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We will have two presentations and by Los Alamos theorists:, Condensed Matter Physics Seminar9:30am
11/24
We will have two presentations and by Los Alamos theorists:, Condensed Matter Physics Seminar
Tuesday, November 24th, 2020
09:30 AM - 11:00 AM
Storrs Campus online
We will have two presentations and by Los Alamos theorists:
9:30-10:00 Shizeng Lin (Los Alamos)
Switching of valley polarization and topology in twisted bilayer graphene by electric currents
The associated manuscript is available at https://arxiv.org/abs/2002.02611.
10:00-10:30 Jian Xin Zhu (Los Alamos)
Signatures of Spin Polarized Fermi Arcs in the Quasiparticle Interferences of CeBi
Ref.: arXiv:2008.10628
10:30-11:00 Discussion
Zoom Meeting:
https://kth-se.zoom.us/j/62068067873 -
Prof A. Balatsky, Department of Physics, University of Connecticut, "Dynamic Quantum Matter and Dark Matter Detection ", Graduate Student Seminar12:15pm
11/20
Prof A. Balatsky, Department of Physics, University of Connecticut, "Dynamic Quantum Matter and Dark Matter Detection ", Graduate Student Seminar
Friday, November 20th, 2020
12:15 PM - 01:15 PM
Storrs Campus online
Prof A. Balatsky,
Department of Physics,
University of Connecticut
Dynamic Quantum Matter and Dark Matter Detection
I will give an overview of activities in the group: starting with the challenge and recent theoretical and experimental progress in identifying the dynamic and entangled orders in quantum materials. As a simple, yet new case I will describe the phenomenon of dynamic multiferroicity in STO and comment on the challenge of detection of quantum hidden orders that require multimode quantum probes. Further, I will discuss proposed applications of quantum materials outside of "usual suspect list", like the use of quantum materials as detectors for Dark Matter. -
Graduate Student Kemal Tezgin, Department of Physics, University of Connecticut, "Theoretical and Phenomenological Studies of the Nucleon Structure in High Energy Reactions ", PhD Dissertation Defense1:00pm
11/18
Graduate Student Kemal Tezgin, Department of Physics, University of Connecticut, "Theoretical and Phenomenological Studies of the Nucleon Structure in High Energy Reactions ", PhD Dissertation Defense
Wednesday, November 18th, 2020
01:00 PM - 03:00 PM
Storrs Campus Video meeting
Graduate Student Kemal Tezgin, Department of Physics,
University of Connecticut
Theoretical and Phenomenological Studies of the Nucleon Structure in High Energy Reactions
The understanding of the internal structure of the proton and other strongly interacting particles is at the forefront of modern nuclear physics research. Generalized Parton Distribution Functions (GPDs) are a powerful tool to advance the understanding of the hadron structure. In addition to the information about the one- dimensional collinear momentum distributions of partons (quarks, anti-quarks, and gluons) known from studies of high energy deep-inelastic reactions, GPDs also carry information on the distribution of partons in the transverse plane, and allow us in this way to access the three-dimensional structure of the nucleon. GPDs can be studied in hard-exclusive reactions and contain also information on the energy-momentum tensor form factors which will allow us to gain insights on quantities like pressure or angular momentum distribution inside the nucleon. The goal of this thesis is to deepen our understanding of the three-dimensional structure of the nucleon. We investigate energy-momentum tensor form factors and densities, and all leading-twist GPDs in the bag model. This quark model provides a consistent theoretical framework to investigate many general concepts that have recently attracted interest, and allows one to study insightful limits like the large-Nc limit, heavy-quark limit, or the non-relativistic limit. Another important aspect of this thesis is the discussion of the monopole and quadrupole contributions to the angular momentum density. Finally, the description of pseudoscalar meson production in exclusive processes in terms of GPDs is discussed in the Goloskokov-Kroll model and implemented in the PARTONS framework, a software development project which will provide direct support for experiments at the Jefferson National Lab and the future Electron-Ion Collider. -
Theoretical and Phenomenological Studies of the Nucleon Structure in High Energy Reactions , Doctoral Dissertation Oral Defense Of Kemal Tezgin1:00pm
11/18
Theoretical and Phenomenological Studies of the Nucleon Structure in High Energy Reactions , Doctoral Dissertation Oral Defense Of Kemal Tezgin
Wednesday, November 18th, 2020
01:00 PM - 02:30 PM
Storrs Campus Zoom
Theoretical and Phenomenological Studies of the Nucleon Structure in High Energy Reactions
In high energy collisions, Parton Distribution Functions (PDFs) are fundamental objects to describe one-dimensional collinear momentum distributions of partons (quarks, anti-quarks, and gluons) inside the nucleon. In addition to PDFs, Generalized Parton Distribution Functions (GPDs) also carry information on the distribution of partons in the transverse plane to its motion and allow us to access the three-dimensional structure of the nucleon. On the other hand, energy-momentum tensor (EMT) densities allow us to access the pressure, shear forces, and angular momentum density inside the nucleon. The goal of this thesis is to deepen our understanding of the three-dimensional structure of the nucleon. We investigate energy-momentum tensor (EMT) form factors and densities, and all leading-twist GPDs in the bag model, formulated in the large-N_c limit. We also evaluate all leading-twist chiral-odd GPDs of the relativistic nucleon in the bag model. The consistency of this quark model allows us to investigate many general concepts that have recently attracted interest, including pressure, shear forces, and angular momentum density. Another important aspect of this thesis is to discuss that the monopole and quadrupole contributions to the angular momentum density can be generated from each other uniquely in a model-independent way. The last chapter is dedicated to the phenomenology of GPDs and the Goloskokov-Kroll model's implementation in the PARTONS framework for pseudoscalar meson production in exclusive processes. -
Dr. Vivienne Baldassare, Washington State Univeristy , "Searching for active galactic nuclei in low-mass galaxies via optical variability", Astronomy Seminar11:00am
11/18
Dr. Vivienne Baldassare, Washington State Univeristy , "Searching for active galactic nuclei in low-mass galaxies via optical variability", Astronomy Seminar
Wednesday, November 18th, 2020
11:00 AM - 12:00 PM
Storrs Campus online
Dr. Vivienne Baldassare, Washington State Univeristy
Searching for active galactic nuclei in low-mass galaxies via optical variability
The present-day population of supermassive black holes in low-mass galaxies offers a window into massive black hole formation in the early universe. While we cannot yet observe the formation of "black hole seeds" at high redshift, the fraction of small galaxies that host a supermassive black hole -- and the properties of those black holes -- are thought to depend on the mechanism by which they form. However, black holes in the smallest galaxies can be difficult to find, requiring creative new approaches. I will discuss recent work showing that long-term optical photometric variability in low-mass galaxies can identify active galactic nuclei that are missed by other selection techniques. I will present an analysis of the nuclear variability of more than 70,000 nearby galaxies and discuss our sample of low-mass, variability-selected supermassive black holes. Using this sample, we also begin to place meaningful constraints on the present-day black hole occupation fraction at low galaxy stellar masses.
Webex link: https://uconn-cmr.webex.com/meet/yah14006 -
Prof A. Puckett, Department of Physics, University of Connecticut, Graduate Student Seminar12:15pm
11/13
Prof A. Puckett, Department of Physics, University of Connecticut, Graduate Student Seminar
Friday, November 13th, 2020
12:15 PM - 01:15 PM
Storrs Campus online
Prof A. Puckett,
Department of Physics,
University of Connecticut
Sub-femtoscale structure of strongly interacting matter from "hard" electron-nucleus collisions
The emergence of nucleon structure and dynamics from strong interactions among its elementary quark and gluon constituents is one of the most difficult and interesting problems in all of physics. The strong interaction, NOT the electroweak Higgs mechanism, is responsible for the dynamical generation of the mass of approximately 98% of all ordinary matter in the universe. Scattering of ultrarelativistic electron beams from nucleon and nuclear targets is the tool of choice for the precision study of nucleon structure. The Super BigBite Spectrometer (SBS) at Jefferson Lab, a novel device currently being installed in JLab's experimental Hall A, with the first beam tentatively expected in 2021, will facilitate a focused program of high-impact nucleon structure measurements in electron-nucleon scattering at large momentum transfer. In this talk I will give an overview of the upcoming SBS program and opportunities for graduate student involvement. -
Professor Saroj Prasad Dash, Quantum Device Physics Laboratory, Dept. Microtechnology and Nanoscience, Chalmers University of Technology, Sweden, "Spin Current in Topological Quantum Materials", Condensed Matter Physics Seminar10:00am
11/10
Professor Saroj Prasad Dash, Quantum Device Physics Laboratory, Dept. Microtechnology and Nanoscience, Chalmers University of Technology, Sweden, "Spin Current in Topological Quantum Materials", Condensed Matter Physics Seminar
Tuesday, November 10th, 2020
10:00 AM - 11:00 AM
Storrs Campus online
Professor Saroj Prasad Dash,
Quantum Device Physics Laboratory, Dept. Microtechnology and Nanoscience,
Chalmers University of Technology, Sweden
Spin Current in Topological Quantum Materials
An outstanding feature of topological quantum materials is their unique spin topology in the electronic band structures with an expected novel charge‐to‐spin conversion effects. In the Weyl semimetal candidate WTe2 we observed both conventional1 and unconventional2 charge‐to‐spin conversion effects at room temperature. In addition to the conventional spin Hall and Rashba--Edelstein effects, we also measured an unconventional charge‐to‐spin conversion component in WTe2. Such a large spin polarization can be possible in WTe2 due to a reduced crystal symmetry combined with its large spin Berry curvature, spin--orbit interaction with a novel spin‐texture of the Fermi states. We also investigated giant Rashba spin-orbit materials BiTeBr to detect the current induced spin polarization at room temperature.3 Furthermore, we integrated graphene with a topological insulator4,5 in van der Waals heterostructures6 to engineer proximity-induced spin-charge conversion phenomena. In these heterostructures, we experimentally demonstrate a gate-tunable spin-galvanic effect at room temperature, allowing for efficient conversion of a non-equilibrium spin polarization into a transverse charge current.7 These findings provide an efficient route for realizing all-electrical and gate-tunable spin phenomenon in topological materials and their heterostructures.
References:
1. Observation of charge to spin conversion in Weyl semimetal at room temperature.
B Zhao, D Khokhriakov, Y Zhang, H Fu, B Karpiak, AM Hoque, X Xu, Y Jiang, B Yan, SP Dash.
Physical Review Research 2 (1), 013286 (2020).
2. Unconventional charge-to-spin conversion Weyl Semimetal WTe2. B Zhao, B Karpiak, D Khokhriakov, A Johansson, AM Hoque, X Xu, Y Jiang, I Mertig, SP Dash. Advanced Materials, 2000818 (2020).
3. Electrically controlled spin injection from giant Rashba spin-orbit conductor BiTeBr"
Z Kovács-Krausz et al., Nano Letters 20, 7, 4782--4791 (2020).
4. Origin and evolution of surface spin current in topological insulators
A Dankert, P Bhaskar, D Khokhriakov, IH Rodrigues, B Karpiak, MV Kamalakar, S Charpentier, I Garate, SP Dash.
Phys. Rev. B 97, 125414 (2018).
5. Room Temperature Electrical Detection of Spin Polarization in Topological Insulators
A Dankert, J. Geur, M.V. Kamalakar, SP Dash;
Nano Letters 15 (12) 7976 (2015).
6. Tailoring emergent spin phenomena in Dirac material heterostructures.
D Khokhriakov, A. W. Cummings, K Song, M Vila, B Karpiak, A Dankert, S Roche and SP. Dash.
Science Advances, 4, 9, eaat9349 (2018)
7. Gate-tunable Spin-Galvanic Effect in Graphene - Topological insulator van der Waals Heterostructures at Room Temperature. D Khokhriakov, AM Hoque, B Ka -
Jacob Franklin, Department of Physics, University of Connecticut, "Quantum sensing for nanoscale magnetic imaging", Graduate Student Seminar12:15pm
11/6
Jacob Franklin, Department of Physics, University of Connecticut, "Quantum sensing for nanoscale magnetic imaging", Graduate Student Seminar
Friday, November 6th, 2020
12:15 PM - 01:15 PM
Storrs Campus online
Jacob Franklin,
Department of Physics,
University of Connecticut
Quantum sensing for nanoscale magnetic imaging
Nanoscale resolution of the properties of materials often plays a crucial role in the pursuit of explanations for exotic phenomena in such materials. These phenomena, such as high temperature superconductivity and frustrated magnetic states, have very exciting potential for practical applications, such as quantum computing. In the Sochnikov Lab, we use state-of-the-art sensors called SQUIDs to probe the magnetic properties of materials and generate magnetic maps at their surfaces. These images are on the order of micrometers in spatial resolution and play an important role in the study of the aforementioned phenomena, for example, because they can be used to analyze the formation and interaction of domains in response to parameters like temperature, auxiliary magnetic field, or strain. I will present some of the fundamental materials research work I have done in the Sochnikov Lab, in which I and my lab mates have taken a direct role in both measurement and analysis. In addition, I will share my experience with instrumentation development projects like the construction of custom-built piezoelectric scanners, the improvement of wiring in our cryostats, the coding of a GUI system for the plotting of data, and the improvement of our data interpolation functions. -
Mohammad Akhshik, Department of Physics, University of Connecticut, "REQUIEM-2D: REsolving QUIEscent Magnified galaxies using strong gravitational lensing, 2D grism spectroscopy and multi-band photometry", Astronomy Seminar10:00am
11/4
Mohammad Akhshik, Department of Physics, University of Connecticut, "REQUIEM-2D: REsolving QUIEscent Magnified galaxies using strong gravitational lensing, 2D grism spectroscopy and multi-band photometry", Astronomy Seminar
Wednesday, November 4th, 2020
10:00 AM - 11:00 AM
Storrs Campus online
Mohammad Akhshik, Department of Physics, University of Connecticut
REQUIEM-2D: REsolving QUIEscent Magnified galaxies using strong gravitational lensing, 2D grism spectroscopy and multi-band photometry
Despite the tremendous progress that has been made in the last decade in studying massive high redshift (z~2) quiescent galaxies, their formation pathways and quenching mechanisms have not yet been established observationally. In my talk, I will review the REQUIEM^2D galaxy survey of eight strong lensed quiescent galaxies at z=1.6-2.9, our attempt to understand the formation scenarios of quiescent galaxies by analyzing the spatially resolved stellar populations with deep HST grism spectroscopy. After briefly reviewing our methodology, I will discuss the results from our REQUIEM^2D pilot target, MRG-S0851, a gravitationally lensed quintuply imaged massive compact red galaxy at z=1.9. Using our recovered ages and SFHs from the joint spectrophotometric analysis, along with trajectories in the UVJ and FUVVJ color-color diagrams, I show that MRG-S0851 is consistent with an early forming, slow quenched galaxy that is going through a centrally-concentrated rejuvenation phase.
Dr. Daniel Walker, Department of Physics, University of Connecticut
Uncovering the hidden star formation in the Milky Way's Central Molecular Zone
As our nearest "extreme environment", the Central Molecular Zone (CMZ, inner few hundred parsecs of our Galaxy) offers an ideal laboratory in which to study the extent to which the process of star formation is sensitive to differing environmental conditions. At a distance of just 8.1 kpc, we can study this process from Galactic scales all the way down to protostellar scales, something that is not possible in extragalactic analogues. In this talk, I will give an overview of our current understanding of star formation in this region of the Galaxy. I will then present some results from recent and ongoing projects that are transforming our view of the CMZ, and providing insight into key questions concerning the role of galactic environment in the star formation process.
Meeting Link: https://uconn-cmr.webex.com/meet/cab16109 -
Prof Jeremy Levy, Department of Physics and Astronomy, University of Pittsburgh, "Ferroelastic Textures, Magnetism, and Superconductivity in LaAlO3/SrTiO3", Condensed Matter Physics Seminar10:00am
11/3
Prof Jeremy Levy, Department of Physics and Astronomy, University of Pittsburgh, "Ferroelastic Textures, Magnetism, and Superconductivity in LaAlO3/SrTiO3", Condensed Matter Physics Seminar
Tuesday, November 3rd, 2020
10:00 AM - 11:00 AM
Storrs Campus online
Prof Jeremy Levy, Department of Physics and Astronomy, University of Pittsburgh
Ferroelastic Textures, Magnetism, and Superconductivity in LaAlO3/SrTiO3
LaAlO3/SrTiO3 heterostructures exhibit a wide range of phenomena that are not well understood. The most prominent are the existence of superconductivity at very low densities, which has been known for more than half a century, and magnetism, which is a more recent discovery. Here I will review experiments that directly probe and/or control these effects at nanoscale dimensions, and suggest that there are strong couplings between ferroelastic domain structure (texture) in LaAlO3/SrTiO3 and both magnetism and superconductivity. I will also examine a connection between some reports of magnetism in transport experiments and phenomena related to superconductivity.
Zoom Meeting:
https://kth-se.zoom.us/j/69230357179 -
Profs. Gerald Dunne and Jon Trump, Department of Physics, University of Connecticut, "Black Holes: The 2020 Nobel Prize in Physics", The 2020 Nobel Prize In Physics (Physics Department Colloquium)3:30pm
10/30
Profs. Gerald Dunne and Jon Trump, Department of Physics, University of Connecticut, "Black Holes: The 2020 Nobel Prize in Physics", The 2020 Nobel Prize In Physics (Physics Department Colloquium)
Friday, October 30th, 2020
03:30 PM - 04:30 PM
Storrs Campus online
Profs. Gerald Dunne and Jon Trump, Department of Physics, University of Connecticut
Black Holes: The 2020 Nobel Prize in Physics
The Nobel Foundation has awarded the 2020 Nobel Prize in Physics to Roger Penrose "for the discovery that black hole formation is a robust prediction of the general theory of relativity", and to Reinhard Genzel and Andrea Ghez "for the discovery of a supermassive compact object at the centre of our galaxy".
See https://www.nobelprize.org/prizes/physics/2020/summary/
We review the physics and the significance of these remarkable discoveries. There will be some technical detail but the talk is intended for a general audience.
Webex link: https://uconn-cmr.webex.com/meet/jot16106 -
Dr. Bradford Snios, Harvard-Smithsonian Center for Astrophysics, "Kinematics of extragalactic jets", Graduate Student Seminar12:15pm
10/30
Dr. Bradford Snios, Harvard-Smithsonian Center for Astrophysics, "Kinematics of extragalactic jets", Graduate Student Seminar
Friday, October 30th, 2020
12:15 PM - 01:15 PM
Storrs Campus online
Dr. Bradford Snios, Harvard-Smithsonian Center for Astrophysics
Kinematics of extragalactic jets
Extragalactic jets emitted from active galactic nuclei are a well-established phenomenon. These jets are known to propagate with bulk relativistic motion over kiloparsec-scale distances, generating emission across multiple energy bands, including the X-ray. In my talk, I will discuss recent X-ray observations investigated for proper motions and brightness changes in nearby jets. Using multi-epoch observations spanning several years, proper motions from X-ray emission are detected for the first time in extragalactic systems, with superluminal motions measured up to speeds of 6.3c. Brightness variations up to 73% are found for the X-ray knots in the jets, and spectroscopic modeling is used to determine cooling emission mechanisms from the sources. These results provide invaluable constraints on the kinematic evolution of these exotic extragalactic systems. -
Prof. Elena Dormidontova, Department of Physics, University of Connecticut, "Soft Matter Physics: HPC Simulations and Theory", Graduate Student Seminar12:15pm
10/23
Prof. Elena Dormidontova, Department of Physics, University of Connecticut, "Soft Matter Physics: HPC Simulations and Theory", Graduate Student Seminar
Friday, October 23rd, 2020
12:15 PM - 01:15 PM
Storrs Campus online
Prof. Elena Dormidontova,
Department of Physics,
University of Connecticut
Soft Matter Physics: HPC Simulations and Theory
Soft matter includes a broad range of structurally different materials ranging from small molecules such as lipids and liquids crystals to macromolecules, biopolymers and colloids. These materials can self-assemble into different organized structures and possess properties which vary depending on external conditions. To be able to understand the principles of self-assembly, predict and direct the outcomes of it is highly desirable to gain fundamental insight into biological self-assembly and to be able to create new materials with desired properties for energy, photonic, nanoelectronics, nanomedicine, sensors and other advanced functional nanomaterials. Theory and molecular modeling play an increasingly important role in gaining fundamental insights into complex behavior of these systems, as it allows to achieve atomistic level details inaccessible experimentally or guide experimental material development by predicting self-assembly pathways depending on structural properties of the building elements and external conditions. Several examples of ongoing, recently funded and planned interdisciplinary research projects collaboration with experimental groups will be discussed in connection with corresponding computer modeling approaches and material applications. -
Prof. Erin Scanlon, Department of Physics, University of Connecticut, "An Introduction to Physics Education Research", Graduate Student Seminar12:15pm
10/16
Prof. Erin Scanlon, Department of Physics, University of Connecticut, "An Introduction to Physics Education Research", Graduate Student Seminar
Friday, October 16th, 2020
12:15 PM - 01:15 PM
Storrs Campus online
Prof. Erin Scanlon,
Department of Physics,
University of Connecticut
An Introduction to Physics Education Research
Physics education research (PER) is a subfield of physics that focuses on investigating questions such as: 1) how can we teach physics better?; 2) how do students learn physics?; and 3) how can we make the physics community more inclusive, equitable, and diverse? In this talk, we will give an introduction to PER, including common misconceptions, methods, and the PER happening at UConn. -
Dr. Viktor Mokeev, Jefferson National Laboratory, "Advances in the Exploration of the Nucleon Resonance Spectrum and Structure in Experimentswith CLAS and CLAS12", Particle, Astrophysics, And Nuclear Physics Seminar2:00pm
10/12
Dr. Viktor Mokeev, Jefferson National Laboratory, "Advances in the Exploration of the Nucleon Resonance Spectrum and Structure in Experimentswith CLAS and CLAS12", Particle, Astrophysics, And Nuclear Physics Seminar
Monday, October 12th, 2020
02:00 PM - 03:00 PM
Storrs Campus online
Dr. Viktor Mokeev, Jefferson National Laboratory
Advances in the Exploration of the Nucleon Resonance Spectrum and Structure in Experimentswith CLAS and CLAS12
Studies of nucleon resonances (N*) in experiments with electromagnetic probes offer unique information on many facets of the strong interaction in the regime of large (on the order of unity) QCD running couplings seen in the generation of the spectrum of N* states with different quantum numbers and structural features. The current status of the N* spectrum and structure studies for exclusive meson photo- and electro-production data with CLAS at Jefferson Lab will be presented in the talk. The extension of these efforts in the Jefferson Lab 12 GeV-era experiments with CLAS12 will be outlined.
WebEx Meeting: https://uconn-cmr.webex.com/uconn-cmr/j.php?MTID=mb3e4c57467ee718677987ca3a427a21d -
Dr. James Guillochon, Berkshire Gray, "From Black Holes, to Data Science, to Robots: Tips & tricks for going into industry", Physics Colloquium: From Black Holes To Robots3:30pm
10/9
Dr. James Guillochon, Berkshire Gray, "From Black Holes, to Data Science, to Robots: Tips & tricks for going into industry", Physics Colloquium: From Black Holes To Robots
Friday, October 9th, 2020
03:30 PM - 04:30 PM
Storrs Campus BPB-131
Dr. James Guillochon, Berkshire Gray
From Black Holes, to Data Science, to Robots: Tips & tricks for going into industry
The majority of physics/astronomy PhD recipients now leave the field for industry either immediately after graduation or after one or more postdoctoral stints. This has been driven by several factors, including the overproduction of PhDs relative to a declining pool of available tenure-track positions, greater freedom to choose where to live, and often significantly higher salaries. However, STEM graduates are increasingly finding that data science, the de facto refuge for former academics, is itself becoming somewhat saturated, with data on recent job listings suggesting that the majority of DS positions are now filled by bachelor's degree recipients rather than PhDs. In this talk, I will describe how I navigated this increasingly complicated landscape to find my current job, and share some pieces of advice I feel are generically useful to those who might be looking for jobs outside of academia in the next few years.
_______
Dr. James Guillochon received a PhD in astrophysics from the University of California Santa Cruz and then went on to hold prestigious postdoctoral fellowships, the Hubble and ITC fellowships, at the Harvard-Smithsonian Center for Astrophysics. He developed a reputation as a world-renowned researcher in a range of topics, including black hole mergers, tidal disruption events, white dwarf accretion, and more. He is also well-known for his open-source contributions to the scientific community, including vox charta, open access astronomy catalogs, software, as well as maintaining a current list of US and Canadian astrophysics graduate program policies regarding the use of the physics GRE in graduate admissions decisions here.
In 2018 Dr. Guillochon transitioned to working in the industry as a Robotics Engineer in the Boston area. He is an outspoken advocate for positive transitions from academia to industry and will be joining us for a virtual colloquium on Friday to discuss his transition. -
Dr. Hossein Sadeghpour, Institute for Theoretical Atomic, Molecular and Optical Physics, Harvard-Smithsonian Center for Astrophysics, "Quantum electron scattering", Graduate Student Seminar12:15pm
10/9
Dr. Hossein Sadeghpour, Institute for Theoretical Atomic, Molecular and Optical Physics, Harvard-Smithsonian Center for Astrophysics, "Quantum electron scattering", Graduate Student Seminar
Friday, October 9th, 2020
12:15 PM - 01:15 PM
Storrs Campus online
Dr. Hossein Sadeghpour,
Institute for Theoretical Atomic, Molecular and Optical Physics, Harvard-Smithsonian Center for Astrophysics
Quantum electron scattering
The second quantum revolution is upon us and atomic molecular and optical (AMO) physics is the discipline leading this revolution. Major advances in cooling and trapping of atoms and molecules in the last three decades now allow practitioners to create exotic many-body systems whose properties and behavior are predicated on fluctuations inherent in quantum systems. The ultracold AMO systems can be precisely and exquisitely interrogated and manipulated to engineer few-body interactions that "nature" may not naturally provide. I'll draw on some fundamental physics concepts to elucidate a few of these quantum many-body features. -
Dr. Semeon Valgushev, Brookhaven National Lab, "Phase diagram of QCD and Lifshitz regime: how transverse thermal fluctuations might turn nuclear matter into quantum-spin liquid", Particle, Astrophysics, And Nuclear Physics Seminar2:00pm
10/5
Dr. Semeon Valgushev, Brookhaven National Lab, "Phase diagram of QCD and Lifshitz regime: how transverse thermal fluctuations might turn nuclear matter into quantum-spin liquid", Particle, Astrophysics, And Nuclear Physics Seminar
Monday, October 5th, 2020
02:00 PM - 03:00 PM
Storrs Campus online
Dr. Semeon Valgushev, Brookhaven National Lab
Phase diagram of QCD and Lifshitz regime: how transverse thermal fluctuations might turn nuclear matter into quantum-spin liquid
We discuss dense cool QCD where a region with spatially inhomogeneous condensate might emerge. In that case, QCD phase diagram may exhibit a Lifshitz regime, which can appear either instead of, or in addition to Critical End Point. We study the Lifshitz regime using a combination of large-N expansion and numerical lattice simulations of an effective O(N) sigma model. We find evidence that quantum fluctuations disorder inhomogeneous condensate ("chiral spirals") and give rise to unusual quantum spin-liquid phase. We also discuss how this novel phase can be detected experimentally.
Zoom Meeting Link:
https://us02web.zoom.us/j/8192648596?pwd=WFkzK1VXa2V4ZVRVNC90ZnM3NDdlQT09
Meeting ID: 819 264 8596
Passcode: 9lYjMG
Note: The seminar will start at 2:00PM, but participants are welcomed to join the meeting at 1:30PM for discussion. -
Prof. M. Gai, Department of Physics, University of Connecticut, "Oxygen Formation in Stellar Helium Burning", Graduate Student Seminar12:15pm
10/2
Prof. M. Gai, Department of Physics, University of Connecticut, "Oxygen Formation in Stellar Helium Burning", Graduate Student Seminar
Friday, October 2nd, 2020
12:15 PM - 01:15 PM
Storrs Campus online
Prof. M. Gai, Department of Physics, University of Connecticut
Oxygen Formation in Stellar Helium Burning
The Laboratory for Nuclear Science (LNS) at Avery Point (http://astro.uconn.edu), aka the Laboratory for Astrophysics, is engaged in research of several problems central to stellar Evolution theory. Today we shall discuss oxygen formation is stellar helium burning, that determines the C/O ratio in stars. This is an essential laboratory input to stellar evolution theory that for example determines the final fate of a Type II supernova (black hole or neutron star), as well as the light curve of a Type Ia supernova (that is used to measure distances to the end of the observable universe from which the accelerated expansion of the universe was recently discovered).
This presentation will involve our faculty at Avery Point (Gai) and in the UK (Smith) and the two graduate students (Stern and Schweitzer) who are working on experiments at Duke University in the USA, in Warsaw, Poland, and in a new facility constructed in Romania. -
Prof. Richard Milner MIT, Physics Colloquium: Visualizing The Proton3:30pm
9/25
Prof. Richard Milner MIT, Physics Colloquium: Visualizing The Proton
Friday, September 25th, 2020
03:30 PM - 04:30 PM
Storrs Campus Remote
Prof. Richard Milner
MIT
Abstract:
Nuclear physicists have recently made progress in understanding how to visualize the fundamental structure of the proton. Electrons scattered from the proton's charged constituents produce snapshots that offer the possibility to produce for the first time a coherent 3D image of the proton. The basic
elements of the technique will be outlined and ongoing experiments at Jefferson Laboratory as well as future experiments at the planned Electron-Ion Collider (EIC) at Brookhaven Laboratory will be described.
Remote Connection info:
TBA -
Graduate Student Benjamin Commeau, Department of Physics, University of Connecticut, "Two Studies on Topological Properties of Organic Superconductors and a new Quantum Dynamical Simulation Algorithm", PhD Dissertation Defense2:00pm
9/25
Graduate Student Benjamin Commeau, Department of Physics, University of Connecticut, "Two Studies on Topological Properties of Organic Superconductors and a new Quantum Dynamical Simulation Algorithm", PhD Dissertation Defense
Friday, September 25th, 2020
02:00 PM - 04:00 PM
Storrs Campus Video meeting
Graduate Student Benjamin Commeau, Department of Physics,
University of Connecticut
Two Studies on Topological Properties of Organic Superconductors and a new Quantum Dynamical Simulation Algorithm
In this thesis I investigate two research topics in topological organic superconductors and one research topic in variational algorithms for quantum computation.
In the first chapter we investigate the structural and electronic properties of the three structural phases alpha, beta and kappa of (BEDT-TTF)2I3, by performing state of the art ab initio calculations in the framework of density functional theory. We furthermore report about the irreducible representations of the corresponding electronic band structures, symmetry of their crystal structure, and discuss the origin of band crossings.
Additionally, we discuss the chemically induced strain in kappa-(BEDT-TTF)2I3 achieved by replacing the iodine layer with other Halogens: Fluorine, Bromine and Chlorine. In the case of kappa-(BEDT-TTF)2F3, we identify topologically protected crossings within the band structure. These crossings are forced to occur due to the non-symmorphic nature of the crystal. In the second chapter, we performed structural optimization and electronic structure calculations in the framework of density functional theory, incorporating, first, the recently developed strongly constrained and appropriately normed semilocal density functional SCAN, and, second, van der Waals corrections to the PBE exchange correlation functional by means of the dDsC dispersion correction method.
In the case of alpha-(BEDT-TTF)2F3 the formation of over-tilted Dirac-type-II nodes within the quasi 2-dimensional Brillouin zone can be found.
For kappa-(BEDT-TTF)2F3, the recently reported topological transition within the electronic band structure cannot be revealed. In the third chapter, we propose a new algorithm called Variational Hamiltonian Diagonalization (VHD), which approximately transforms a given Hamiltonian into a diagonal form that can be easily exponentiated. VHD allows for fast forwarding, and removes Trotterization error and allows simulation of the entire Hilbert space. We prove an operational meaning for the VHD cost function in terms of the average simulation fidelity. Moreover, we prove that the VHD cost function does not exhibit a shallow-depth barren plateau. Our numerical simulations verify that VHD can be used for fast-forwarding dynamics.
Zoom Link: https://harvard.zoom.us/j/92203325795?pwd=T2VoYzNPNkwvZW1GWFlhQk9Ga1lwUT09 -
Prof. T. Blum, Department of Physics, University of Connecticut, "Lattice QCD at UConn", Graduate Student Seminar12:15pm
9/18
Prof. T. Blum, Department of Physics, University of Connecticut, "Lattice QCD at UConn", Graduate Student Seminar
Friday, September 18th, 2020
12:15 PM - 01:15 PM
Storrs Campus online
Prof. T. Blum, Department of Physics, University of Connecticut
Lattice QCD at UConn
I will give a brief introduction to the Standard Model of Particle Physics, and Quantum Chromodynamics (QCD) in particular. I will then describe how we solve QCD using large scale numerical simulations. I will finish with a few current and important examples. -
Graduate Student Saman Bastami, Department of Physics, University of Connecticut, "Studies on Hadron Structure through Transverse-Momentum-Dependent Parton Distribution Functions", PhD Dissertation Defense1:15pm
9/11
Graduate Student Saman Bastami, Department of Physics, University of Connecticut, "Studies on Hadron Structure through Transverse-Momentum-Dependent Parton Distribution Functions", PhD Dissertation Defense
Friday, September 11th, 2020
01:15 PM - 03:15 PM
Storrs Campus Video meeting
Graduate Student Saman Bastami, Department of Physics,
University of Connecticut
Studies on Hadron Structure through Transverse-Momentum-Dependent Parton Distribution Functions
The detailed description of hadrons in terms of quarks and gluons, the fundamental degrees of freedom of Quantum Chromodynamics, is an open problem. Important aspects of hadron structure can be studied in certain deep-inelastic high-energy processes which have revealed important insights about the longitudinal momentum distributions of quarks and gluons inside hadrons. Our knowledge of the three-dimensional structure is still very limited. Transverse momentum dependent parton distribution functions (TMDs) are one of the main tools to study the transverse structure of hadrons through processes such as semi-inclusive deep inelastic scattering SIDIS) or the Drell-Yan process. This dissertation is dedicated to phenomenological and model studies of TMDs.
All spin and azimuthal asymmetries of the lepton-nucleon SIDIS are calculated at leading- and subleading twist exploring the so-called "Wandzura-Wilczek-type" approximation which consists in a systematic neglect quark-gluon correlations. The results are obtained using available phenomenological information on TMDs as well as constraints from state-of-the-art lattice QCD calculations, and compared to the experimental data from HERMES, COMPASS and Jefferson Lab.
The asymmetries of the pion-induced Drell-Yan process with polarized protons are studied at leading twist. The information about TMDs is taken from non-perturbative calculations in the lightfront constituent quark model, the spectator model and, where available, phenomenological extractions of TMDs. The results are compared to recent data from the first polarized pion-nucleon Drell-Yan experiment performed by the COMPASS Collaboration at CERN, and predictions for future experiments are made.
The "covariant parton model", an effective hadronic model based on the intuitive parton model concept, is extended and formalized. This allows one to compute all time-reversal-even TMDs of leading and subleading twist in a systematic way. This model naturally supports the Wandzura-Wilczek-type approximations and predicts several non-trivial relations between TMDs, many of which are supported in other model frameworks and can be tested in experiments. Applications and limitations of the model are discussed.
Meeting video link: https://zoom.us/j/96866754697?pwd=NEM1WUt3VkxhbVdQQWdacVVubHNvQT09 -
Prof. D. McCarron, Department of Physics, University of Connecticut, "A quantum-leap towards next generation technologies", Graduate Student Seminar12:15pm
9/11
Prof. D. McCarron, Department of Physics, University of Connecticut, "A quantum-leap towards next generation technologies", Graduate Student Seminar
Friday, September 11th, 2020
12:15 PM - 01:15 PM
Storrs Campus online
Prof. D. McCarron, Department of Physics, University of Connecticut
A quantum-leap towards next generation technologies
Recent progress manipulating quantum systems has led to a second quantum revolution that is developing new technologies that leverage the laws of nature at small scales. This talk will give an overview of some of these new technologies alongside their applications - with an emphasis on ultracold systems cooled to one millionth of a degree above absolute zero. I will draw links between these applications and my own research program before giving a brief summary of our experimental progress.
Research Group URL: http://themccarrongroup.com -
Doctoral Dissertation Oral Defense of Saman Bastami1:30pm
9/7
Doctoral Dissertation Oral Defense of Saman Bastami
Monday, September 7th, 2020
01:30 PM - 03:00 PM
Other Zoom
Studies on Hadron Structure through Transverse Momentum Dependent Parton Distribution Functions -
Graduate Student Brandon A. Clary, Department of Physics, University of Connecticut, "Exclusive Phi Production Beam Spin Asymmetry Measurements with CLAS12", PhD Dissertation Defense9:30am
8/21
Graduate Student Brandon A. Clary, Department of Physics, University of Connecticut, "Exclusive Phi Production Beam Spin Asymmetry Measurements with CLAS12", PhD Dissertation Defense
Friday, August 21st, 2020
09:30 AM - 11:30 AM
Storrs Campus Video meeting
Graduate Student Brandon A. Clary, Department of Physics,
University of Connecticut
Exclusive Phi Production Beam Spin Asymmetry Measurements with CLAS12
Measurements of the beam spin asymmetry (BSA) of the exclusive electroproduction of the vector phi(1020) meson through its decay into charged Kaons have been performed. The data set used was based on the RG-A run period from the recently upgraded CEBAF Large Acceptance Spectrometer (CLAS12) in Hall B at Jefferson National Lab (JLab). The run period used a 10.6 GeV longitudinally polarized electron beam and an unpolarized hydrogen target. The available statistics collected allow for detailed studies of the W, -t, xB, and Q2 dependencies of the BSA amplitudes from vector phi meson production. The BSA measurements will shed light on the exchange mechanisms responsible for phi production at JLab energies. In this dissertation, a non-zero BSA is observed, which suggests a possible enhancement of pseudo-scalar exchange mechanism near phi production threshold. Therefore, the non-zero BSA may be a result of the interference of the pseudo-scalar exchange mechanism with a scalar one. Ultimately, information on the dominant exchange mechanism will aid in the development of a Generalized Parton Distribution (GPD) based description of these processes in the context of hard to soft transition.
Webex link: https://uconn-cmr.webex.com/uconn-cmr/j.php?MTID=m0844eee0d13477ad76f35797ae8467db -
Dr. D. Farfurnik, University of Maryland, "Enhancing the coherence properties of quantum dots toward quantum photonic applications", Condensed Matter Physics Seminar10:00am
7/14
Dr. D. Farfurnik, University of Maryland, "Enhancing the coherence properties of quantum dots toward quantum photonic applications", Condensed Matter Physics Seminar
Tuesday, July 14th, 2020
10:00 AM - 11:00 AM
Storrs Campus online
Dr. D. Farfurnik, University of Maryland
Enhancing the coherence properties of quantum dots toward quantum photonic applications
Self-assembled Quantum Dots (QD) exhibit some of the best single photon emission properties, including nearly ideal efficiency and indistinguishability. As such, and considering their compatibility with nanofabrication techniques, on-chip integration of QDs as single photon emitters and non-linear components plays a key role in integrated photonic-based information processing and may pave the way toward the creation of quantum networks. Manipulating and storing quantum information utilizing QD spins, however, is limited by their short coherence times originating from interactions with a nuclear bath. In this talk, I will describe our approaches for addressing this challenge: First, the application of dynamical decoupling (DD) pulse sequences prolongs the coherence times by decoupling the QD spins from the environment. While the performance of such protocols is often limited by the accumulation of pulse imperfections, arbitrary spin control enabling composite and concatenated sequencing could further enhance the achievable spin control fidelities [1]. Such a sequencing is implementable by driving a Lambda system of the QD utilizing an optical signal arbitrarily modulated by a temperature-stabilized electro optical modulator (EOM). I will present a recent experimental demonstration of such a control [2], our analysis for optimizing the EOM working point for enhancing the achievable optical rotation Rabi frequencies, as well as the efficiency of the protocol for QDs strongly coupled to L3 photonic crystal cavities. Second, the resulting coherence properties may be further enhanced by utilizing molecules of coupled QDs (QDM), which offer a singlet-triplet ground state decoherence-free subspace [3]. Beyond the promising combination of such a subspace with the application of DD sequences, leveraging the isolated optical transitions of the QDM may offer single-shot spin readout capabilities. I will present our approach for implementing such a spin readout incorporating microwave pi-pulses, its experimental feasibility utilizing optimally designed transmission lines, and the expected readout fidelities based on the achievable microwave Rabi frequencies [4].
[1] D. Farfurnik et al., ``Optimizing a dynamical decoupling protocol for solid-state electronic spin ensembles in diamond'', Phys. Rev. B 92, 060301(R) (2015)
[2] J.H. Bodey et al., ``Optical spin locking of a solid-state qubit'', npj Quantum Information 5, 95 (2019)
[3] D. Kim et al., ``Ultrafast optical control of entanglement between two quantum-dot spins'', Nat. Phys. 7, 223--229 (2011)
[4] D. Farfurnik et al., ``Experimental realization of time-dependent phase-modulated continuous dynamical decoupling'', Phys. Rev. A 96, 013850 (2017)
Zoom Meeting: https://kth-se.zoom.us/j/61809414846 -
Graduate Student Daniel McNeel, Department of Physics, University of Connecticut, "Shape Coexistence in \(^{28}\)Mg: Structure of a Transitional Nucleus", PhD Dissertation Defense1:00pm
6/11
Graduate Student Daniel McNeel, Department of Physics, University of Connecticut, "Shape Coexistence in \(^{28}\)Mg: Structure of a Transitional Nucleus", PhD Dissertation Defense
Thursday, June 11th, 2020
01:00 PM - 03:00 PM
Storrs Campus Video meeting
Graduate Student Daniel McNeel, Department of Physics,
University of Connecticut
Shape Coexistence in \(^{28}\)Mg: Structure of a Transitional Nucleus
The structure of nuclei outside the region of stability is an area of ongoing experimental research. Recent investigations in the region around \(^{32}\)Mg have discovered inversions in the usual ordering of shell model states. From these discoveries, theories of the evolution towards this "island of inversion" predict low-lying deformed intruder states for several nuclei in the region. One such nucleus, which exists in the region of transition between the normal and inverted hierarchies, is \(^{28}\)Mg. In this nucleus the ground state is expected to be mixed, i.e. it is a superposition of nearby \(0^+\) neutron pairing configurations. An excited intruder \(0^+\) state will have a different configuration and shape than surrounding states, a property known as shape coexistence.
Multi-nucleon transfer is known to be sensitive to the static deformation of a nucleus. It is also sensitive to both the amplitude and phase of configuration mixed states, and enhances transfer to those states which are similar to the ground state of the target plus two nucleons in single particle orbitals. This makes it a valuable tool to investigate the properties of \(^{28}\)Mg. The two-neutron adding reaction \(^{26}\)Mg(t,p)\(^{28}\)Mg has been used to study the properties of the ground state and excited \(0^+\) states. This experiment was carried out at Argonne National Laboratory using the HELIcal Orbit Spectrometer (HELIOS). HELIOS was designed to overcome the difficulties of measuring reactions in inverse kinematics. Experiments in inverse kinematics consist of a heavy particle, in this case \(^{26}\)Mg, incident on the light particle (\(^3\)H).
Because multi-nucleon transfers are more complex than single particle transfers, a calculation of the nuclear structure must guide the understanding of which configurations will be strongly populated. Shell model calculations have been used to evaluate the structure related transfer amplitudes, which were used as input into Distorted Wave Born Approximation (DWBA) calculations for the reaction. The results of this analysis are the relative contributions of different configurations to the ground state and excited \(0^+\) states, which provide a stringent test of the theoretical prediction of shape coexistence and intruder states.
Video link: https://uconn-cmr.webex.com/meet/dgm14002 -
Graduate Student Matthew Phelps, Department of Physics, University of Connecticut, "Cosmological Fluctuations in Standard and Conformal Gravity", PhD Dissertation Defense10:00am
6/2
Graduate Student Matthew Phelps, Department of Physics, University of Connecticut, "Cosmological Fluctuations in Standard and Conformal Gravity", PhD Dissertation Defense
Tuesday, June 2nd, 2020
10:00 AM - 12:00 PM
Storrs Campus Video meeting
Graduate Student Matthew Phelps, Department of Physics,
University of Connecticut
Cosmological Fluctuations in Standard and Conformal Gravity
In the theory of cosmological perturbations, extensive methods of simplifying the equations of motion and eliminating non-physical gauge modes are required in order to construct the perturbative solutions. One approach, standard within modern cosmology, is to decompose the metric perturbation into a basis of scalars, vectors, and tensors defined according to their transformation behavior under three-dimensional rotations (the S.V.T. decomposition). By constructing a projector formalism to define the basis components, we show that such a decomposition is intrinsically non-local and necessarily incorporates spatially asymptotic boundary conditions. We continue application of the S.V.T. decomposition and solve the fluctuation equations exactly within standard cosmologies as applied to both Einstein gravity and conformal gravity, finding that in general the various S.V.T. gauge-invariant combinations only decouple at a higher-derivative level. To match the underlying transformation group of General Relativity and thus provide a manifestly covariant formalism, we introduce an alternate scalar, vector, tensor basis with components defined according to general four-dimensional coordinate transformations. In this basis, the fluctuation equations greatly simplify, where one can again decouple them into separate gauge-invariant sectors at the higher-derivative level. In the context of conformal gravity, we use similar constructions to solve the fluctuation equations exactly within any geometry that is conformal to flat and show that in a radiation era Robertson-Walker cosmology, fluctuations grow as \(t^4\).
Video Meeting URL: https://uconn-cmr.webex.com/meet/map14010 -
Prof. Chiara Mingarelli, Department of Physics, University of Connecticut, "Probing supermassive black hole mergers with pulsar timing", Graduate Student Seminar12:15pm
4/24
Prof. Chiara Mingarelli, Department of Physics, University of Connecticut, "Probing supermassive black hole mergers with pulsar timing", Graduate Student Seminar
Friday, April 24th, 2020
12:15 PM - 01:15 PM
Storrs Campus video conferencing
Prof. Chiara Mingarelli, Department of Physics, University of Connecticut
Probing supermassive black hole mergers with pulsar timing
Galaxy mergers are a standard aspect of galaxy formation and evolution, and most (likely all) large galaxies contain supermassive black holes. As part of the merging process, the supermassive black holes should in-spiral together and eventually merge, generating a background of gravitational radiation in the nanohertz regime. An array of precisely timed pulsars spread across the sky can form a galactic-scale gravitational wave detector in this band. I describe the current efforts to develop and extend the pulsar timing array concept, together with recent limits which have emerged from international efforts to constrain astrophysical phenomena at the heart of supermassive black hole mergers. -
Graduate Student Lukasz Kuna, Department of Physics, University of Connecticut, "Mesoscale Studies of Nanostructured Multi-Functional Materials", PhD Dissertation Defense10:00am
4/16
Graduate Student Lukasz Kuna, Department of Physics, University of Connecticut, "Mesoscale Studies of Nanostructured Multi-Functional Materials", PhD Dissertation Defense
Thursday, April 16th, 2020
10:00 AM - 12:00 PM
Storrs Campus Video meeting
Graduate Student Lukasz Kuna,
Department of Physics,
University of Connecticut
Mesoscale Studies of Nanostructured Multi-Functional Materials
In this dissertation, multiple studies centered around functional properties of materials for applications in devices and novel technologies are carried out utilizing a mesoscale modeling approach. The studies involve simulating the properties of dielectric nano/microstructures with coupled polar and elastic degrees of freedom and developing a greater understanding of their dependence on the structure size, morphology and applied external conditions. Of particular focus in this work are optical properties of electroactive materials including zero- and one-dimensional structures such as nanoparticles and nanowires, as well as mesoscopic functional properties of larger structures such as polycrystalline ceramics (with submicron grain sizes) and ferroelectric mesa structures. The first two research topics are focused on the band gap properties of 1-D semiconductors and modeling of ferroelectric mesa structures, each study serving as an important tool in progressing the understanding of these materials for functional applications. The final topic, comprising the larger portion of the work, presents a novel approach for studying transmission in nanocrystalline ceramics based upon wave-train theory, that is then utilized to predict light transmission in polycrystalline ceramics. In particular, simulations examining the optical properties modulation under different applied mechanical and electrical boundary conditions predict large changes to transmission, including switching from full transparency to opacity in some instances. The results presented in this dissertation highlight an extraordinary promise of functional nano- and microceramics for a wide range of advanced engineering applications. -
Prof. L. Levitov, Department of Physics, MIT, "Long-Lived Excitations, Directional Memory and Hydrodynamic Transport in Two-Dimensional Electron Fluids", Condensed Matter Physics Seminar9:00am
4/10
Prof. L. Levitov, Department of Physics, MIT, "Long-Lived Excitations, Directional Memory and Hydrodynamic Transport in Two-Dimensional Electron Fluids", Condensed Matter Physics Seminar
Friday, April 10th, 2020
09:00 AM - 10:00 AM
Storrs Campus online
Prof. L. Levitov, Department of Physics, MIT
Long-Lived Excitations, Directional Memory and Hydrodynamic Transport in Two-Dimensional Electron Fluids
It was found recently that 2D electron fluids can support collective excitations that are not subject to Landau's \(T^2\) dissipation [1,2,3]. This surprising behavior originates from the head-on carrier collisions, a process that dominates angular relaxation at not-too-high temperatures \(T \ll T_F\) due to the joint effect of Pauli blocking and kinematic constraints. As a result, a large family of exceptionally long-lived excitations emerges, associated with the odd-parity harmonics of momentum distribution. This leads to "tomographic" dynamics: fast 1D spatial diffusion along the unchanging velocity direction accompanied by a slow angular dynamics that gradually randomizes velocity orientation. The abnormally slow angular relaxation originates from correlated angular dynamics involving "lock-step'' angular displacements along the Fermi surface occurring in collinear two-particle collisions. The slow loss of directional memory is described as non-Brownian angular random walk, "superdiffusion" on the Fermi surface. The collective behavior with directional memory dominates at moderately long times, pushing the onset of conventional hydrodynamics to abnormally large timescales. The tomographic regime features an unusual hierarchy of time and length scales, resulting in scale-dependent transport coefficients. The scale dependence manifests itself in fractional-power current flow profiles and unusual conductance scaling vs. temperature and sample size. This exotic behavior can be directly probed by transport measurement techniques, as well as by momentum-resolved tunneling measurements.
1. P J Ledwith, H Guo, L Levitov, The Hierarchy of Excitation Lifetimes in Two-Dimensional Fermi Gases,
Annals of Physics 411, 167913 (2019)
2. P J Ledwith, H Guo, A V Shytov, L Levitov,
Tomographic Dynamics and Scale-Dependent Viscosity in Two-Dimensional Electron Systems,
Phys Rev Lett 123, 116601 (2019)
3. P J Ledwith, H Guo, L Levitov, Angular Dynamics and Directional Memory in Two-Dimensional Electron Fluids,
2019
Zoom Meeting: https://kth-se.zoom.us/j/123036826 -
Prof. G. Fernando, Department of Physics, University of Connecticut, "Quasi-two-dimensional organics, Hubbard ladders, and dynamic stability", Graduate Student Seminar12:15pm
4/3
Prof. G. Fernando, Department of Physics, University of Connecticut, "Quasi-two-dimensional organics, Hubbard ladders, and dynamic stability", Graduate Student Seminar
Friday, April 3rd, 2020
12:15 PM - 01:15 PM
Storrs Campus video conferencing
Prof. G. Fernando, Department of Physics, University of Connecticut
Quasi-two-dimensional organics, Hubbard ladders, and dynamic stability
This presentation is a summary of several projects we have been working on during the past few years.
Our work covers electronic structure calculations of selected organic materials, searches for Dirac and Weyl materials as well as many-body physics of small clusters. In addition, recent developments in time crystal ideas are being examined at the many-body level. Our main interests are focused on several active areas in condensed matter physics such as topological materials, phase separation in small Hubbard clusters, unconventional superconductivity such as odd-frequency or photo-molecular high temperature superconductivity, frustrated magnetic systems such as quantum spin liquids and transport properties in two-dimensional systems. In addition, there is an ongoing effort on probing some fundamental aspects of quantum mechanics.
The link to the presentation:
https://physics.uconn.edu/wp-content/uploads/sites/2234/2020/04/phys_seminar_apr3_20.pptx -
Dr. Raffaella DeVita, INFN Genoa and Jefferson Lab, "Hadron spectroscopy in the light quark sector", Particle, Astrophysics, and Nuclear Physics Seminar2:00pm
3/30
Dr. Raffaella DeVita, INFN Genoa and Jefferson Lab, "Hadron spectroscopy in the light quark sector", Particle, Astrophysics, and Nuclear Physics Seminar
Monday, March 30th, 2020
02:00 PM - 03:00 PM
Storrs Campus GS-413E
Dr. Raffaella DeVita, INFN Genoa and Jefferson Lab
Hadron spectroscopy in the light quark sector -
Prof. Masafumi Fukuma, Kyoto University , "Title/abstract TBA", Particle, Astrophysics, and Nuclear Physics Seminar2:00pm
3/23
Prof. Masafumi Fukuma, Kyoto University , "Title/abstract TBA", Particle, Astrophysics, and Nuclear Physics Seminar
Monday, March 23rd, 2020
02:00 PM - 03:00 PM
Storrs Campus GS-413E
Prof. Masafumi Fukuma, Kyoto University
Title/abstract TBA -
CANCELLED:, Dr. J. Nathan Hohman, Institute of Materials Science and the Department of Chemistry, University of Connecticut, CANCELLED: Condensed Matter Physics Seminar2:00pm
3/17
CANCELLED:, Dr. J. Nathan Hohman, Institute of Materials Science and the Department of Chemistry, University of Connecticut, CANCELLED: Condensed Matter Physics Seminar
Tuesday, March 17th, 2020
02:00 PM - 03:00 PM
Storrs Campus GS 119
CANCELLED:
Dr. J. Nathan Hohman,
Institute of Materials Science and the Department of Chemistry, University of Connecticut
Self-Assembly of Low-Dimensional Nanomaterials in Crystalline Ensemble
When reduced in size to the nanoscale, materials express compelling new phenomena. For example, a single layer abstracted from graphite leads to fantastic new properties in graphene, or a nanocrystal of gold takes on new optical properties as a nanoparticle. Making materials very small or very thin has been an easy way to prepare exciting new materials--for example, the 2D transition metal dichalcogenides (TMDCs) have a long history of investigation prior to the recent interest in their monolayers for applications in photovoltaics, electrocatalysts, and spintronic materials. 2D phases have been uncovered for a number of elements and binary semiconductors, although many compounds do not share the same propensity to form 2D structures. Through the use of hybrid materials like hybrid perovskites and metal organic chalcogenide assemblies (MOCHAs), low-dimensional nanostructures can be prepared that are part of a crystalline ensemble, unlocking new portions of the period table to the exploration of low-dimensional phases. Importantly, hybrid materials combine organic components which enables structural and electronic direction at the molecular scale. Here, we consider the structure and organization of mithrene- silver benzeneselenolate- a self-assembling layered hybrid structure, and examine its optoelectronic properties in the context of a 2D-like material. Synthetic manipulation of dimensionality and topology is used to prepare a family of related crystalline polymer systems, and the role of intermolecular forces and molecular geometry on the inorganic phases are considered in the context of transitions between 1D, 2D, and 3D coordination polymer systems. -
Due to the current health situation and concerns surrounding the Corona virus, we are canceling the Katzenstein Lecture and Banquet scheduled for Friday, March 13, 2020., CANCELLED: 24th Annual Katzenstein Distinguished Lecture4:00pm
3/13
Due to the current health situation and concerns surrounding the Corona virus, we are canceling the Katzenstein Lecture and Banquet scheduled for Friday, March 13, 2020., CANCELLED: 24th Annual Katzenstein Distinguished Lecture
Friday, March 13th, 2020
04:00 PM - 05:00 PM
Storrs Campus Student Union Theater
Due to the current health situation and concerns surrounding the Corona virus, we are canceling the Katzenstein Lecture and Banquet scheduled for Friday, March 13, 2020.
Presented by the UConn Physics Department, the Katzenstein Distinguished Lecture series continues this spring. This year's program features Professor Donna Strickland of the University of Waterloo, 2018 Nobel Prize winner in Physics for co-inventing chirped pulse amplification, a technique for creating high-intensity ultrashort optical pulses. More information about Professor Strickland can be found at https://physics.uconn.edu/2020/03/04/professor-donna-strickland-katzenstein-distinguished-lecturer-march-13-2020/ -
Prof. A. Wuosmaa, Department of Physics, University of Connecticut, "Exotic Nuclei -- Modern Directions in Nuclear Physics", Graduate Student Seminar12:15pm
3/13
Prof. A. Wuosmaa, Department of Physics, University of Connecticut, "Exotic Nuclei -- Modern Directions in Nuclear Physics", Graduate Student Seminar
Friday, March 13th, 2020
12:15 PM - 01:15 PM
Storrs Campus GS-119
Prof. A. Wuosmaa, Department of Physics, University of Connecticut
Exotic Nuclei -- Modern Directions in Nuclear Physics
The study of so-called "exotic nuclei" -- atomic nuclei with a large imbalance between the number of neutrons and protons -- is a major focus of nuclear-physics research today. Our understanding of the structure of nuclei far from stability is rather poor in comparison to what we know about stable nuclei, and that knowledge is important for understanding, for example, violent events in the cosmos responsible for the synthesis of the chemical elements. I will discuss some basics of nuclear structure, some examples where nuclear structure influences astrophysics, and how we can study the properties of exotic nuclei in the laboratory. Finally, I will describe a new accelerator facility that will be completed within the next two years which will enable a deeper understanding of the properties of exotic nuclei and will provide many new opportunities for research. -
Dr. Sumanta Bandyopadhyay, Nordita, "Superconductivity in a nonhermitian system and Berezinksii classification ", Condensed Matter Physics Seminar2:00pm
3/11
Dr. Sumanta Bandyopadhyay, Nordita, "Superconductivity in a nonhermitian system and Berezinksii classification ", Condensed Matter Physics Seminar
Wednesday, March 11th, 2020
02:00 PM - 03:00 PM
Storrs Campus GS 119
Dr. Sumanta Bandyopadhyay,
Nordita
Superconductivity in a nonhermitian system and Berezinksii classification
We have investigated the effects of nonhemriticty on superconducting states. Nonhermiticity enters our system due to electrons leaking out of/into (in case of pumping) the system. We have explicitly constructed several unconventional pairing amplitudes in nonhermitian systems in thep resence and absence of the particle-hole symmetry. We find nonhermitian dynamics induces odd frequency superconducting states, and we present the related experimental observables. We have further studied the robustness of the Berezinskii classification [1] of anomalous pairing amplitude in the presence of the nonhermiticity and shown that SP∗OT∗=−1 symmetry withstands nonhermiticity. -
CANCELLED:, Dr. A. B. Belonoshko, Department of Physics, Royal Institute of Technology, Sweden, CANCELLED: Condensed Matter Physics Seminar2:00pm
3/10
CANCELLED:, Dr. A. B. Belonoshko, Department of Physics, Royal Institute of Technology, Sweden, CANCELLED: Condensed Matter Physics Seminar
Tuesday, March 10th, 2020
02:00 PM - 03:00 PM
Storrs Campus GS 119
CANCELLED:
Dr. A. B. Belonoshko,
Department of Physics, Royal Institute of Technology, Sweden
Iron under extreme conditions
I will report the latest theoretical data on the iron phase diagram. A particular emphasis will be on the stabilization of the high-PT body-centered cubic (bcc) Fe under conditions of the Earth Inner Core [1] and how its stabilization interfere in the interpretation of iron melting curve and resolution of related enigmatic questions.
The mechanism of the high-PT bcc Fe phase stabilization is quite unique. The atoms in this structure move at times as in a liquid [2]. Therefore, the mean square displacement never saturates and the diffusion coefficient and the viscosity of the bcc Fe are similar to those in very viscous liquid [3].
Recently, our theoretical prediction of the stability of high-PT bcc Fe phase [1,4] was confirmed by diamond anvil cell experiments [5]. Interesting, that when a number of the experimental studies analyzed with the knowledge of the physics of the bcc Fe phase, those experiments confirm the stability of the new phase rather than contradict it.
I will show how the X-ray diffraction pattern of the bcc Fe looks like and discuss whether similar XRD patterns have already been observed in Fe high-PT melting experiments. I will demonstrate that the stabilization of the bcc phase was at times misinterpreted as melting.
The similarity of the bcc and liquid iron under extreme conditions of pressure and temperature revives the speculations on the existence of the critical solid-liquid point.
Acknowledgments: This work was supported by the Swedish Research Council.
[1] A. B. Belonoshko, T. Lukinov, J. Fu, J. Zhao, S. Davis, S. I. Simak Nature Geoscience 10, 312 (2017).
[2] https://www.youtube.com/watch?v=s5Rl7mtxiEY
[3] A. B. Belonoshko, J. Fu, T. Bryk, S. I. Simak, M. Mattesini, Nature Communications 10, 1-7 (2019).
[4] A. B. Belonoshko, R. Ahuja, B. Johansson, Nature 424, 1032 (2003).
[5] R. Hrubiak, Y. Meng, G. Shen, arXiv:1804.05109 Experimental evidence of a body centered cubic iron at the Earth's core conditions. -
Dr. Ali Kaya, Department of Physics, Harvard University, "Challenging the initial condition prescriptions in quantum cosmology", Physics Colloquium (Dr. Ali Kaya)3:30pm
3/6
Dr. Ali Kaya, Department of Physics, Harvard University, "Challenging the initial condition prescriptions in quantum cosmology", Physics Colloquium (Dr. Ali Kaya)
Friday, March 6th, 2020
03:30 PM - 04:30 PM
Storrs Campus BPB-131
Dr. Ali Kaya, Department of Physics, Harvard University
Challenging the initial condition prescriptions in quantum cosmology
Determining the initial state of the universe is a challenging problem in quantum cosmology and there are popular suggestions like the no boundary (Hawking & Hartle) and the tunneling (Vilenkin) prescriptions.
After briefly reviewing the problem, we argue that the quantum theory of gravity must resolve the big-bang singularity either by yielding a regular past eternal evolution or by a smooth finite beginning; in both cases the initial state can in principle be totally arbitrary that need not to be restricted by any ad-hoc principle. We illustrate this point in a minisuperspace toy model where there is a smooth beginning of the universe provided by the matter Hamiltonian degenerating to the zero operator. This simple model also illustrates how quantum gravity may resolve the big-bang singularity. -
Prof. A. Balatsky, Department of Physics, University of Connecticut and NORDITA, "Materials Informatics and Quantum Matter ", Graduate Student Seminar12:15pm
3/6
Prof. A. Balatsky, Department of Physics, University of Connecticut and NORDITA, "Materials Informatics and Quantum Matter ", Graduate Student Seminar
Friday, March 6th, 2020
12:15 PM - 01:15 PM
Storrs Campus GS-119
Prof. A. Balatsky, Department of Physics, University of Connecticut and NORDITA
Materials Informatics and Quantum Matter
High-throughput calculations using first-principles methods in combination with approaches from data mining and machine learning fields have enabled a new stage in accelerated discovery of functional materials with special properties. I will present newly developed Organic Materials Database (OMDB, https://omdb.diracmaterials.org/) and discuss use of these methods. Our platform hosts thousands of electronic structures of synthesized organic materials [1] and is a useful tool in searching for novel materials. I will also discuss the implemented tools to predict and search magnetic structure factors and exchange coupling of organic materials in our database. Our work is a step towards a new way to search for novel functional materials characterized by a specific pattern in their electronic structure, for example, Dirac materials, topological insulators [2,3]. I will also present the ongoing work on the dynamics of quantum matter, where we predict transient collective instabilities in driven quantum systems [4].
[1] Stanislav S. Borysov http://et.al, (2017), PLoS ONE 12(2): http://e0171501.doi:10.137 https://doi.org/10.1371/journal.pone.0171501
[2] R. M. Geilhufe, S. S. Borysov, D. Kalpakchi, A.V. Balatsky, Physical Review Materials 2:2, (2018): 024802
[3] R. Matthias Geilhufe, Bart Olsthoorn, Alfredo D. Ferella, Timo Koski, Felix Kahlhoefer, Jan Conrad and Alexander V. Balatsky, Phys. Status Solidi RRL, 2018, 12, 1800293. S. Borysov et al, npj Computational Materials volume 4, Article number: 46 (2018)
[4] A Pertsova, AV Balatsky, Dynamically Induced Excitonic Instability in Pumped Dirac Materials, Annalen der Physik, 1900549 (2020) -
Prof. M. Gai, Department of Physics, University of Connecticut, "The Big Bang", Graduate Student Seminar12:15pm
2/28
Prof. M. Gai, Department of Physics, University of Connecticut, "The Big Bang", Graduate Student Seminar
Friday, February 28th, 2020
12:15 PM - 01:15 PM
Storrs Campus GS-119
Prof. M. Gai, Department of Physics, University of Connecticut
The Big Bang
The Big Bang theory is one of the most fundamental theory of nature. In particular Big Bang Nucleosynthesis (BBN) is a parameter free theory, that gave one of the first and strongest evidence for the Big Bang theory. Current observation of primordial elements (that were produced during BBN), that are measured in some cases with an accuracy nearing 1%, are predicted at the same level of accuracy, with excellent agreement with observation. But one nagging problem remains: the production of 7Li in BBN is approximately a factor 3 and close to 5 sigma smaller than the prediction of BBN. This problem has been known over the last forty years as the "Primordial 7Li Problem".
We will review the Big Bang theory and BBN and describe an attempt to solve the lithium problem in the Master work of Emily Kading at UConn. We conclude that currently, there is still no standard solution to the lithium problem. -
Charles Reynolds Distinguished Lecture, Charles Reynolds Distinguished Lecture (Prof. Peter Abbamonte, U. of Illinois)3:30pm
2/21
Charles Reynolds Distinguished Lecture, Charles Reynolds Distinguished Lecture (Prof. Peter Abbamonte, U. of Illinois)
Friday, February 21st, 2020
03:30 PM - 04:30 PM
Storrs Campus BPB-131
Charles Reynolds Distinguished Lecture
"Bose Condensation of Excitons in a Transition Metal Dichalcogenide"
Professor Peter Abbamonte
University of Illinois
Urbana, IL
Bose condensation has shaped our understanding of macroscopic quantum phenomena, having been realized in superconductors, atomic gases, and liquid helium. Excitons are bosons that have been predicted to condense into either a superfluid or an insulating electronic crystal. But definitive evidence for a thermodynamically stable exciton condensate has never been achieved. In this talk I will describe our use of momentum-resolved electron energy-loss spectroscopy (M-EELS) to demonstrate the existence of an exciton condensate in the transition metal dichalcogenide semimetal, 1T‐TiSe2. This phase of matter was predicted in the 1960's and nicknamed "excitonium" by Halperin and Rice, but not realized for certain until now. I will discuss the experimental signature of exciton condensation, a plasmon that disperses to zero energy at the transition temperature, and latest results on its stability against carrier doping and hydrostatic pressure. -
Dr. Evan Philip, Department of Physics & Astronomy, Stony Brook University, "Chiral Photocurrents and Terahertz Emission in Dirac/Weyl Semimetals", Condensed Matter Physics Seminar2:00pm
2/19
Dr. Evan Philip, Department of Physics & Astronomy, Stony Brook University, "Chiral Photocurrents and Terahertz Emission in Dirac/Weyl Semimetals", Condensed Matter Physics Seminar
Wednesday, February 19th, 2020
02:00 PM - 03:00 PM
Storrs Campus GS 119
Dr. Evan Philip, Department of Physics & Astronomy, Stony Brook University
Chiral Photocurrents and Terahertz Emission in Dirac/Weyl Semimetals
I will start with an introduction to Dirac/Weyl semimetals and chiral anomaly. We will then look at a new mechanism for photocurrents in Dirac/Weyl semimetals that relies on the chiral anomaly. I will also discuss terahertz emission from the Weyl semimetal TaAs induced by a near-infrared laser, where Weyl fermions play a central role. We will conclude with remarks on some potential applications of these works. -
Dr. I. Zaliznyak, Brookhaven National Laboratory, "Entropic elasticity and negative thermal expansion in crystalline solids", Condensed Matter Physics Seminar2:00pm
2/18
Dr. I. Zaliznyak, Brookhaven National Laboratory, "Entropic elasticity and negative thermal expansion in crystalline solids", Condensed Matter Physics Seminar
Tuesday, February 18th, 2020
02:00 PM - 03:00 PM
Storrs Campus GS 119
Dr. I. Zaliznyak, Brookhaven National Laboratory
Entropic elasticity and negative thermal expansion in crystalline solids
While most solids expand when heated, some materials show the opposite behavior: negative thermal expansion (NTE). NTE is common in polymers and biomolecules, where it stems from the entropic elasticity of an ideal, freely-jointed chain. The origin of NTE in solids had been widely believed to be different, with phonon anharmonicity and specific lattice vibrations that preserve geometry of the coordination polyhedra -- rigid unit motions (RUMs) -- as leading contenders for explaining NTE. Our neutron scattering study of a simple cubic NTE material, ScF3, overturns this consensus [1]. We observe that the correlation in the positions of the neighboring fluorine atoms rapidly fades on warming, indicating an uncorrelated thermal motion, which is only constrained by the rigid Sc-F bonds. These experimental findings lead us to a quantitative, quasi-harmonic theory of NTE in terms of entropic elasticity of a Coulomb floppy network crystal, which is applicable to a broad range of open framework solids featuring floppy network architecture [2]. Our theory is in remarkable agreement with experimental results in ScF3, accurately describing NTE, phonon frequencies, entropic compressibility, and structural phase transition governed by entropic stabilization of criticality. We thus find that NTE in a family of insulating ceramics stems from the same simple and intuitive physics of entropic elasticity of an under-constrained floppy network that has long been appreciated in soft matter and polymer science, but broadly missed by the "hard" condensed matter community.
Our results reveal the formidable universality of the NTE phenomenon across soft and hard matter [1,2].
[1] D. Wendt, et al., Sci. Adv. 5: eaay2748. (2019).
[2] A. V. Tkachenko, I. A. Zaliznyak. arXiv:1908.11643 (2019). -
Dr. Andrey Sadofyev, Los Alamos National Laboratory, "Spin polarization of gauge bosons in rotating plasma", Particle, Astrophysics, and Nuclear Physics Seminar2:00pm
2/17
Dr. Andrey Sadofyev, Los Alamos National Laboratory, "Spin polarization of gauge bosons in rotating plasma", Particle, Astrophysics, and Nuclear Physics Seminar
Monday, February 17th, 2020
02:00 PM - 03:00 PM
Storrs Campus GS-413E
Dr. Andrey Sadofyev, Los Alamos National Laboratory
Spin polarization of gauge bosons in rotating plasma
I will show that the chiral vortical effect (CVE) known to take place for massless fermions in a rotating system can be, in fact, generalized to particles of arbitrary spin. These effects are particularly interesting since they describe the polarization of quarks, gluons, and photons in rotating QGP produced in heavy-ion collisions. For gauge bosons the local polarization current is not gauge invariant making it harder to use this object on practice. This issue can be resolved if one focuses on a class of gauge-invariant but non-canonical polarization currents of gauge bosons known as zilches. I will further show that CVE for gauge bosons has a counterpart in the general zilch current - zilch vortical effect (ZVE) and discuss how ZVE arises in a simple theoretical setup. -
Prof. G. Dunne, Department of Physics, University of Connecticut, "Scientific Communication: Preparing a Talk, a Proposal, or a Paper", Graduate Student Seminar12:15pm
2/14
Prof. G. Dunne, Department of Physics, University of Connecticut, "Scientific Communication: Preparing a Talk, a Proposal, or a Paper", Graduate Student Seminar
Friday, February 14th, 2020
12:15 PM - 01:15 PM
Storrs Campus GS-119
Prof. G. Dunne, Department of Physics, University of Connecticut
Scientific Communication: Preparing a Talk, a Proposal, or a Paper
An important part of the work of a scientist is to communicate clearly the results of their work, in a way that can be understood by the appropriate audience: scientific, political or general. In this talk I discuss some tips for preparing a paper, a seminar or a proposal, and encourage you to think carefully about this aspect of your work. The good news is that with a little dedicated effort it is a sure way to stand out from the pack and have your work recognized. -
Prof. Lorenzo Sorbo, Department of Physics, University of Massachusetts Amherst, "Particle production during inflation: a case study", Particle, Astrophysics, and Nuclear Physics Seminar2:00pm
2/10
Prof. Lorenzo Sorbo, Department of Physics, University of Massachusetts Amherst, "Particle production during inflation: a case study", Particle, Astrophysics, and Nuclear Physics Seminar
Monday, February 10th, 2020
02:00 PM - 03:00 PM
Storrs Campus GS-413E
Prof. Lorenzo Sorbo, Department of Physics, University of Massachusetts Amherst
Particle production during inflation: a case study
In this talk I will quickly review primordial inflation. After arguing that axion-like inflatons are especially well motivated, I will discuss how a derivative coupling of a pseudoscalar inflaton to vector and to fermions fields can amplify significantly the mode functions of those degrees of freedom which, in their turn, can lead to a very rich phenomenology. -
Prof. Reynold E. Silber, Department of Geology and Geophysics, Yale University, "Transport properties of liquid transition metals at extreme conditions: a lesson from metallic glasses with the forbidden symmetry", Physics Colloquium (Prof. Reynold Silber)3:30pm
2/7
Prof. Reynold E. Silber, Department of Geology and Geophysics, Yale University, "Transport properties of liquid transition metals at extreme conditions: a lesson from metallic glasses with the forbidden symmetry", Physics Colloquium (Prof. Reynold Silber)
Friday, February 7th, 2020
03:30 PM - 04:30 PM
Storrs Campus BPB-131
Prof. Reynold E. Silber, Department of Geology and Geophysics, Yale University
Transport properties of liquid transition metals at extreme conditions: a lesson from metallic glasses with the forbidden symmetry
The Earth's core is a giant heat engine that supports the existence of life on our planet by providing heat to drive mantle convection, plate tectonics and volcanism. The convection of a liquid iron (Fe) alloy in the outer core generates the Earth's magnetic field. However, transport properties of liquid Fe-alloys (e.g., electrical, thermal and viscous transport properties) at extreme core conditions are some of the least constrained parameters. The high pressure experimental measurements of the transport properties are extremely challenging and a general theoretical understanding of the structures of liquid transition metals is still incomplete. Recent successful electrical resistivity measurements of liquid Fe, Ni and Fe-Si alloy at pressures up to 24 GPa show the invariant electrical resistivity along the melting boundaries. It was demonstrated that the Icosahedral Short Range Order (ISRO) structures in liquid transition metals and alloys strongly modulate transport properties at extreme conditions. Supporting evidence for the presence of the ISRO in the Earth's and other terrestrial outer cores comes from the recently discovered quasi-crystalline phases in natural metallic glasses with the forbidden symmetry, previously considered impossible to exist in nature. However, the existence of forbidden fivefold symmetry is not possible without super-cooling of metallic glass forming liquids that contain ISRO structures. Thus, metallic glasses represent one of the convergence points between planetary science and materials science. Here, I first discuss a new paradigm imposed by the ISRO structures on the transport properties of the outer cores of terrestrial planetary bodies. The discussion is then extended toward the important role ISROs play in formation of metallic glasses with exotic properties. Furthermore, I examine the potential application of high pressures toward manufacturing of metallic glasses with customizable concentration of structures with ISRO or any other forbidden symmetry. Considering the important role of metallic glasses in the high tech industry, this research has significant cross-disciplinary implications. -
Prof. I. Sochnikov, Department of Physics, University of Connecticut, "Quantum sensing and imaging of materials", Graduate Student Seminar12:15pm
1/31
Prof. I. Sochnikov, Department of Physics, University of Connecticut, "Quantum sensing and imaging of materials", Graduate Student Seminar
Friday, January 31st, 2020
12:15 PM - 01:15 PM
Storrs Campus GS-119
Prof. I. Sochnikov, Department of Physics, University of Connecticut
Quantum sensing and imaging of materials
I will describe our recent discoveries of fascinating emergent phenomena in several quantum materials, including high temperature and low temperature superconductors. I will provide details of our state-of-the-art experimental systems with a focus on quantum sensing and mesoscopic imaging.
Additionally, I will present my view of what a successful doctorate in experimental physics includes, as well as, what you might expect from our Ph.D. program and how to be successful in it. -
Prof. Dale Kocevski, Colby College, "Connecting Black Hole Growth and Galaxy Evolution Across Cosmic Time", Physics Colloquium (Prof. Dale Kocevski)3:30pm
1/24
Prof. Dale Kocevski, Colby College, "Connecting Black Hole Growth and Galaxy Evolution Across Cosmic Time", Physics Colloquium (Prof. Dale Kocevski)
Friday, January 24th, 2020
03:30 PM - 04:30 PM
Storrs Campus BPB 131
Prof. Dale Kocevski, Colby College
Connecting Black Hole Growth and Galaxy Evolution Across Cosmic Time
Supermassive black holes, and the active galactic nuclei (AGN) that they power, are thought to play an integral role in the evolution of galaxies by acting to regulate, and eventually suppress, the star formation activity of their host galaxies. I will discuss recent efforts to test this proposed connection by studying the demographics of galaxies experiencing active black hole growth. In particular, I will highlight results obtained using infrared imaging from the Hubble Space Telescope, which has allowed us to study galaxies back when the Universe was a quarter of its current age. It is during this era of cosmic history that black hole growth and star formation activity in the Universe are at their peak. I will discuss what Hubble has revealed about the mechanisms that fuel AGN activity at this epoch and the connection between black hole growth and the emergence of the first generation of passive galaxies in the Universe. I will also discuss future work planned with Hubble's successor, the James Webb Space Telescope, which will soon allow us to view the first galaxies and black holes to form after the Big Bang.
Cookies will be served prior to the talk, at 3:00 p.m. outside BPB-131 -
Prof. R. Jones, Department of Physics, University of Connecticut, "Resolving a Mystery in QCD with High Energy Photons", Graduate Student Seminar12:15pm
1/24
Prof. R. Jones, Department of Physics, University of Connecticut, "Resolving a Mystery in QCD with High Energy Photons", Graduate Student Seminar
Friday, January 24th, 2020
12:15 PM - 01:15 PM
Storrs Campus GS-119
Prof. R. Jones, Department of Physics, University of Connecticut
Resolving a Mystery in QCD with High Energy Photons
Almost immediately after QCD was recognized as the correct theory of the strong force, it was realized that in addition to the stable nuclear particles (known hadrons) that had already been seen, other entire families of unstable nuclear particles should also exist, which decay into the known hadrons. These new particles, collectively known as "exotic hadrons", include glueballs, hybrids, tetraquarks, and pentaquarks. Experimental searches for exotics for the past 40 years have mostly turned up empty, until recently. I will describe recent results from the LHC that give convincing evidence of tetraquarks, and a new experiment recently begun at Jefferson Lab to search for hybrids. -
Dr. Matt Orr, California Institute of Technology, "Spatially Resolved Star Formation in Cosmological Zoom-in Simulations: Understanding the Role of Feedback in Scaling Relations", Astronomy Seminar2:00pm
1/22
Dr. Matt Orr, California Institute of Technology, "Spatially Resolved Star Formation in Cosmological Zoom-in Simulations: Understanding the Role of Feedback in Scaling Relations", Astronomy Seminar
Wednesday, January 22nd, 2020
02:00 PM - 03:00 PM
Storrs Campus GS-119
Dr. Matt Orr, California Institute of Technology
Spatially Resolved Star Formation in Cosmological Zoom-in Simulations: Understanding the Role of Feedback in Scaling Relations
Cosmological simulations have evolved over the past two decades to match ever more restrictive constraints on galaxy formation and evolution. For much of this time, simulations struggled to match global properties of observed galaxies: stellar mass--halo mass relations, integrated star formation rates--gas masses (integrated Kennicutt-Schmidt), etc. However, the latest generation of zoom-in simulations is just now able to spatially resolve many of these galaxy scaling relations. In my talk, I will discuss several aspects of spatially resolved galaxy scaling relations in the FIRE (Feedback In Realistic Environments) suite of cosmological zoom-in simulations, among them: Kennicutt-Schmidt, star formation rate profiles, and line of sight gas velocity dispersions correlating with star formation rates. These projects all relating back to the idea that stellar feedback has a central role to play in the emergence of many of these galaxy scaling relations. I will explore how modern cosmological simulations like FIRE, and associated analytic models, are moving closer to observations, both in their results and their ability to model observables directly. -
Dr. Kiryl Pakrouski, Department of Physics, Princeton University, "Automatic design of Hamiltonians", Condensed Matter Physics Seminar2:00pm
1/10
Dr. Kiryl Pakrouski, Department of Physics, Princeton University, "Automatic design of Hamiltonians", Condensed Matter Physics Seminar
Friday, January 10th, 2020
02:00 PM - 03:00 PM
Storrs Campus GS 119
Dr. Kiryl Pakrouski, Department of Physics, Princeton University
Automatic design of Hamiltonians
We formulate an optimization problem of finding optimal Hamiltonians by analogy to the variational principle. Given a variational ansatz for a Hamiltonian we construct a loss function as a weighted sum of relevant Hamiltonian properties specifying thereby the search query. Using fractional quantum Hall effect as a test system we illustrate how the framework can be used to determine a generating Hamiltonian of a finite-size model wavefunction (Moore-Read Pfaffian and Read-Rezayi states) or to find optimal parameters for an experiment. We also discuss how the search for approximate generating Hamiltonians may be used to find simpler and more realistic models implementing the given exotic phase of matter by experimentally accessible interaction terms. -
Dr. GiBaik Sim, Department of Physics, Korea Advanced Institute of Science and Technology, "Interacting spin-3/2 and spin-1 Fermions : Topological superconductivity", Condensed Matter Physics Seminar2:00pm
1/7
Dr. GiBaik Sim, Department of Physics, Korea Advanced Institute of Science and Technology, "Interacting spin-3/2 and spin-1 Fermions : Topological superconductivity", Condensed Matter Physics Seminar
Tuesday, January 7th, 2020
02:00 PM - 03:00 PM
Storrs Campus GS 119
Dr. GiBaik Sim, Department of Physics, Korea Advanced Institute of Science and Technology
Interacting spin-3/2 and spin-1 Fermions : Topological superconductivity
In this talk, I will first discuss generic realization of topological superconductivity in three-dimensional quadratic band touching system. [1]
Based on the interacting Luttinger model, I exhibit that the absence of particle-hole symmetry leads the system to favor the special spin-quintet
superconductors with secondary spin-singlet pairing ; (i) uniaxial nematic phase with secondary spin-singlet pairing \( \left(S_{3z^2-r^2}+s\right)\), (ii) timereversal breaking phase with secondary spin-singlet pairing \( \left( S_{3z^2 -r^2} + S_{xy}+iS_{x^2-y^2} + s \right) \). \( \left(S_{3z^2-r^2}+s\right)\) phase possesses topologically non-trivial nodal rings and drumhead-like surface states. \( \left( S_{3z^2 -r^2} + S_{xy}+iS_{x^2-y^2} + s \right) \) phase contains topologically protected Bogoliubov Fermi pockets and corresponding zero-energy arc states. I will also argue
possible applications of this theory to YPtBi.
As a next step, I will introduce the spin-triplet superconductivity in the
newly discovered form of the topological semimetal, where spin-1 electrons
form triple-band crossings. [2] The peculiar property of spin-1 Fermions is that Fermi statistics rules out on-site spin-singlet pairing. Adopting the Landau theory of spin-triplet pairings, I exhibit that the system stabilizes two
distinct phases ; (i) time-reversal symmetric \(S_z\) phase, (ii) time-reversal breaking \(S_{x}+iS_{y}\) phase. Remarkably, both of these phases have gapless Bogoliubov quasiparticles and furthermore possess topological invariants for each nodal ring or Bogoliubov Fermi surface.
[1] G. Sim, A. Mishra, M. J. Park, Y. B. Kim, G. Y. Cho, and S. Lee, Physical Review B 100, 064509 (2019).
[2] G. Sim, M. J. Park, and S. Lee, arXiv:1909.04015 (2019). -
Dr. Julia Wildeboer, Max Planck Institute for the Physics of complex systems, "Tales from the Quantum Spin Liquid Crypt", Condensed Matter Physics Seminar4:00pm
12/12
Dr. Julia Wildeboer, Max Planck Institute for the Physics of complex systems, "Tales from the Quantum Spin Liquid Crypt", Condensed Matter Physics Seminar
Thursday, December 12th, 2019
04:00 PM - 05:00 PM
Storrs Campus GS-117
Dr. Julia Wildeboer, Max Planck Institute for the Physics of complex systems
Tales from the Quantum Spin Liquid Crypt
Two-dimensional frustrated quantum antiferromagnets can harbor a phase of matter called a quantum spin liquid .This state exhibits no conventional symmetry but emergent, topological order. Remarkably, the spin liquid state has fascinating features such as gapped fractionalized quasiparticle excitations with exotic quantum statistics making it a highly sought after state in the (topological) quantum computation community.
In this talk, I will review properties of a spin liquid state and discuss the concept of quantum entanglement which is an important diagnostic tool when it comes to uncovering the nature of a spin liquid state. I will introduce a family of fractional quantum Hall (FQH) lattice states. Using the Moore-Read lattice state as an example, I will demonstrate how ''FQH physics in lattice systems'' can advance the field by discussing the issue of inserting quasiholes and quasielectrons into the FQH lattice state, the insertion of the latter being impossible in continuum FQH states because of a singularity problem. -
Prof. A. Polkovnikov, Department of Physics, Boston University, "Periodically driven quantum systems", Condensed Matter Physics Seminar2:00pm
12/12
Prof. A. Polkovnikov, Department of Physics, Boston University, "Periodically driven quantum systems", Condensed Matter Physics Seminar
Thursday, December 12th, 2019
02:00 PM - 03:00 PM
Storrs Campus GS-117
Prof. A. Polkovnikov,
Department of Physics,
Boston University
Periodically driven quantum systems
In this talk I will give an overview of periodically driven (Floquet) quantum systems. In particular, after giving a general introduction I will discuss basic ideas of Floquet engineering, relation between the high frequency expansion and the Schrieffer-Wolff transformation, general questions of adiabaticity in such systems, heating and the ways to suppress it. -
Graduate Student Cheng Tu, Department of Physics, University of Connecticut, "Study HVP and HLbL contribution to the muon g - 2 using Lattice QCD ", PhD Dissertation Defense3:00pm
12/10
Graduate Student Cheng Tu, Department of Physics, University of Connecticut, "Study HVP and HLbL contribution to the muon g - 2 using Lattice QCD ", PhD Dissertation Defense
Tuesday, December 10th, 2019
03:00 PM - 05:00 PM
Storrs Campus GS-117
Graduate Student Cheng Tu,
Department of Physics,
University of Connecticut
Study HVP and HLbL contribution to the muon g - 2 using Lattice QCD
The hadronic vacuum polarization (HVP) contribution and long-distance hadronic light-by-light (HLbL) scattering contribution to the muon anomalous magnetic moment are evaluated by using lattice QCD. The HVP calculations are performed with 2 + 1 + 1 flavors of HISQ fermions at the physical pion mass from three ensembles, generated by the MILC collaboration. In the long-distance part of the HLbL contribution, we replace the QCD, four-current connected Green's function from previous HLbL study with the product of two independent πγγ amplitudes, which are joined by an analytic, position space pion propagator. The calculations are performed with near physical pion mass on four different lattice ensembles, which are generated by RBC/UKQCD Collaboration. -
Dr. Adrian Gozar, Applied Physics Department, Yale University , "Optical nano-imaging of novel quantum materials and hetero-structures.", Condensed Matter Physics Seminar2:00pm
12/10
Dr. Adrian Gozar, Applied Physics Department, Yale University , "Optical nano-imaging of novel quantum materials and hetero-structures.", Condensed Matter Physics Seminar
Tuesday, December 10th, 2019
02:00 PM - 03:00 PM
Storrs Campus GS 117
Dr. Adrian Gozar, Applied Physics Department, Yale University
Optical nano-imaging of novel quantum materials and hetero-structures.
'Quantum materials' are platforms for observation of quantum effects at macroscopic scales. Their properties can be often combined in layered structures and are strongly sensitive to external stimuli, suggesting a plausible path towards a new generation of devices with 'on-demand' functionalities. We focus on expanding the material phase-space of these materials and also on finding new ways to probe their surface and interface properties. An example of novel graphitic structures produced in our lab is borophene, a 2D boron allotrope with potential technological uses in flexible electronics and as a precursor to metallic nanotubes. I will discuss synthesis and characterization of large area, up to 100 μm2 in size, single-crystals of borophene on copper surfaces and also ideas for device integration. Scanning near-field optical microscopy (SNOM) is able to probe electronic properties of surface or subsurface crystalline layers despite the presence of underlying metallic substrates. I will illustrate how the lateral and depth resolution are key advantages of SNOM as a non-invasive optical method for device characterization. I will also emphasize the power of this technique for obtaining fundamental information about electron dynamics in hetero-structures. An example is the generation and coupling to novel excitations such as surface Josephson plasma modes in an ultra-thin superconducting film. These results highlight SNOM as a non-invasive tool which is particularly useful for studying interface electron dynamics, imaging states with broken symmetry in correlated systems and topological materials as well as for probing structure, dielectric properties and emergent conduction channels in nano-structures and biological samples. -
Cancelled!, Prof. I. Sochnikov, Department of Physics, University of Connecticut, Cancelled: Graduate Student Seminar12:15pm
12/6
Cancelled!, Prof. I. Sochnikov, Department of Physics, University of Connecticut, Cancelled: Graduate Student Seminar
Friday, December 6th, 2019
12:15 PM - 01:15 PM
Storrs Campus GS-119
Cancelled!
Prof. I. Sochnikov, Department of Physics, University of Connecticut
Quantum sensing and imaging of materials
I will describe our recent discoveries of fascinating emergent phenomena in several quantum materials, including high temperature and low temperature superconductors. I will provide details of our state-of-the-art experimental systems with a focus on quantum sensing and mesoscopic imaging.
Additionally, I will present my view of what a successful doctorate in experimental physics includes, as well as, what you might expect from our Ph.D. program and how to be successful in it. -
Graduate Student Razib Obaid, Department of Physics, University of Connecticut, "Single and multi-photon induced ionization in atoms and molecules", PhD Dissertation Defense10:00am
12/5
Graduate Student Razib Obaid, Department of Physics, University of Connecticut, "Single and multi-photon induced ionization in atoms and molecules", PhD Dissertation Defense
Thursday, December 5th, 2019
10:00 AM - 12:00 PM
Storrs Campus GS-117
Graduate Student Razib Obaid,
Department of Physics,
University of Connecticut
Single and multi-photon induced ionization in atoms and molecules
The response of atomic and molecular species to photoionization is being studied for decades now. These atoms and molecules respond characteristically upon absorption of photons. The interesting question is: how is the energy deposited into the atoms and molecules by absorption of photons ultimately dissipated? The advent and development of X-ray synchrotrons, free-electron lasers and the strong field optical lasers keep ushering new dimensions into this question in terms of the ability of following rapid sequence of events, and, otherwise, identifying hidden relaxation mechanisms.
Through the means of resonant excitation of valence and inner shell electrons of simple atom, such as neon, and cluster-like complex molecular system such as fullerene and endohedral fullerene, we investigated their relaxation mechanisms by absorption of single and multiple photons. At excitation above their characteristic resonances, we observed hitherto unknown time delayed relaxation mechanisms in the structural change of fullerene, interatomic Coulombic decay and incomplete charge transfer processes in endohedral fullerene, and two photon absorption in neon through observation of fluorescence. Furthermore, we also investigated the fragmentation and hydrogen migration dynamics in hydrocarbons to explore the energy dissipation question for biologically relevant systems. The work is worthwhile in that it contributes to the understanding of the ultrafast intrinsic dynamics of various processes and systems relevant to physics, chemistry, and biology. -
Dr. Fatma Aslam, University of Connecticut & Jefferson Lab, "Singularities in twist-3 distributions and QCD vacuum", Particle, Astrophysics, and Nuclear Physics Seminar3:00pm
12/4
Dr. Fatma Aslam, University of Connecticut & Jefferson Lab, "Singularities in twist-3 distributions and QCD vacuum", Particle, Astrophysics, and Nuclear Physics Seminar
Wednesday, December 4th, 2019
03:00 PM - 04:00 PM
Storrs Campus GS-117
Dr. Fatma Aslam, University of Connecticut & Jefferson Lab
Singularities in twist-3 distributions and QCD vacuum
Twist-3 Generalized Parton Distributions may provide an alternative source of information on quark orbital angular momentum. Additionally, twist-3 GPDs embody information on the spatial distribution of quark-gluon correlations. Spectator models are used to study general features that appear in twist-3 GPDs. We find in 1 loop calculations/spectator models that twist-3 generalized parton distributions exhibit discontinuities. In the forward limit these singular contributions grow into delta function contributions. These terms are essential for certain sum rules for twist 3 PDFs and neglecting these terms leads to an apparent violation of these sum rules. We identify these delta function terms with momentum components in the nucleon state that do not scale as the nucleon is boosted to infinite momentum. -
Dr. Brian Svoboda,National Radio Astronomy Observatory, "The earliest phases of high-mass star formation in the Milky Way", Astronomy Seminar2:00pm
12/4
Dr. Brian Svoboda,National Radio Astronomy Observatory, "The earliest phases of high-mass star formation in the Milky Way", Astronomy Seminar
Wednesday, December 4th, 2019
02:00 PM - 03:00 PM
Storrs Campus GS-119
Dr. Brian Svoboda,National Radio Astronomy Observatory
The earliest phases of high-mass star formation in the Milky Way
High-mass stars are key to regulating the interstellar medium, star formation activity, and overall evolution of galaxies, but their formation remains an open problem in astrophysics. In order to understand the physical conditions during the earliest phases of high-mass star formation, I will present observational studies we have carried out on dense molecular clouds that show no signatures of star formation activity. We identify several thousand dense, starless clump
candidates (SCCs) from the 1.1 mm Bolocam Galactic Plane Survey and systematically analyze their physical properties. We further investigate the 12 most high-mass SCCs within 5 kpc using the Atacama Large Millimeter/submillimeter Array (ALMA) to study their sub-structure at high spatial resolution. We find previously undetected low-luminosity protostars in 11 out of 12 SCCs, fragmentation equal to the thermal Jeans length of the clump, and no starless cores exceeding 30 solar masses. While uncertainties remain concerning the star formation efficiency in this sample, these observational facts are consistent with models where high-mass stars form from initially low- to intermediate-mass protostars that accrete most of their mass from the surrounding clump. I will also present on-going research studying gas inflow signatures with GBT/Argus and ALMA, and the dense core mass function with the JVLA. -
Dr. Fazel Tafti, Boston College, "Design Principles for the Kitaev Magnets with Emergent Majorana Fermions ", Condensed Matter Physics Seminar2:00pm
12/4
Dr. Fazel Tafti, Boston College, "Design Principles for the Kitaev Magnets with Emergent Majorana Fermions ", Condensed Matter Physics Seminar
Wednesday, December 4th, 2019
02:00 PM - 03:00 PM
Storrs Campus GS-117
Dr. Fazel Tafti, Boston College
Design Principles for the Kitaev Magnets with Emergent Majorana Fermions
Our progress toward the age of quantum computing requires a new class of materials with long-range spin entanglement and fractionalized excitations known as Majorana fermions. These elusive particles are theoretically predicted to exist in a spin liquid ground state inside a frustrated magnet. Candidate materials for magnetic frustration and the spin liquid state must have strong interactions but lack any magnetic ordering. Instead of an ordered ground state, these materials produce a quantum entangled ground state with coherent spin fluctuations. In this talk, I will explain how such ground states are constructed in magnetic materials by introducing valence bond solids and resonating valence bonds. I will focus on a special class of materials with honeycomb structure and strong magnetic frustration due to bond dependent ferromagnetic interactions. Such materials are described by a Kitaev Hamiltonian that consists of bond dependent anisotropic exchange interactions. I will explain why the current candidate materials have failed to satisfy the predictions of the theory, and provide a potential solution to improve such materials and achieve a true spin liquid ground state. -
Prof. Jie Wu, Westlake University, China, "Electronic nematicity in unconventional superconductors", Condensed Matter Physics Seminar2:00pm
11/26
Prof. Jie Wu, Westlake University, China, "Electronic nematicity in unconventional superconductors", Condensed Matter Physics Seminar
Tuesday, November 26th, 2019
02:00 PM - 03:00 PM
Storrs Campus GS 119
Prof. Jie Wu, Westlake University, China
Electronic nematicity in unconventional superconductors
The mechanism of high temperature superconductivity is a long-standing mystery in condensed matter physics. Despite of the intensive efforts devoted to this topic since its discovery in 1987, the nature of the superconducting state and the normal state remains ambiguous. Starting from an unexpected observation that the voltage transverse to the current direction is not zero in high temperature superconductors (HTS), I will present our investigations for the underlying mechanism, which at the end leads to the picture of the spontaneous breaking of the rotational symmetry in the normal state of HTS. Such a peculiar state is named as the electronic nematic state, implying its origin is the electron-electron correlation and, more importantly, the motion of electrons is anisotropic in the Cu-O plane. This challenges the basics of the Fermi liquid theory that the electrons' motion is isotropic as the word "liquid" implies. By studying how the nematicity evolves with the temperature and the chemical doping, our experiments reach the conclusion that the high temperature superconductivity in fact emerges out of the electronic nematic state. Other unconventional superconductors, such as ruthenate and Fe-based superconductors, show very similar behavior, indicating the electronic nematicity may be deeply correlated with unconventional superconductivity.
I will also briefly discuss our findings of the dependence of the superconducting temperature on the superfluid density, the abnormal independence of the interface superconductivity on the chemical doping, and the charge cluster glass state in the vicinity of the superconductor-insulator transition. All these findings constitute a vague but coherent picture of HTS.
References:
1. J. Wu, A. T. Bollinger, X. He and I. Božović, "Spontaneous breaking of rotational symmetry in copper oxide superconductors", Nature 547, 432-435 (2017).
2. I. Božović, X. He, J. Wu and A. T. Bollinger, "Dependence of the critical temperature in overdoped copper oxides on superfluid density", Nature 536, 309-311 (2016).
3. J. Wu, A. T. Bollinger, J. Sun and I. Božović, "Hall effect in quantum critical charge cluster glass", Proc. Natl. Acad. Sci. USA 113, 4284-4289 (2016).
4. J. Wu, O. Pelleg, G. Logvenov, A. T. Bollinger, J. Sun, G. S. Boebinger, M. Vanević, Z. R adović and I. Božović, "Anomalous independence of interface superconductivity from carrier density", Nature Materials 12, 877-881 (2013).