November 2, 2020 – Elaina Hancock – UConn Communications The Sloan Digital Sky Survey’s fifth generation – a groundbreaking project to bolster our understanding of the formation and evolution of galaxies, including the Milky Way – collected its very first observations on the evening of October 23. Image: The Sloan Digital Sky Survey’s fifth generation […][Read More]
Kyungseon Joo, a professor of physics, has been named Chair of the CLAS Collaboration, one of the largest international collaborations in nuclear physics. CLAS involves 50 institutions from 9 countries and has about 250 collaborators. The collaboration recently completed the upgrade of the CEBAF Large Acceptance Spectrometer (CLAS12) for operation at 11 GeV beam energy […][Read More]
Could traveling into the past be part of our future? Quite possibly, says Ron Mallett, a UConn emeritus professor of physics who has studied the concept of time travel for decades. Earlier this month, he spoke with NBC Connecticut reporter Kevin Nathan about his life and work as a theoretical physicist, and discussed how time […][Read More]
The UConn Physics Department is delighted to announce that our 2019 Distinguished Katzenstein Lecturer will be Professor Dame Jocelyn Bell Burnell. Professor Dame Jocelyn Bell Burnell is world-famous for her discovery of pulsars in 1967. Pulsars are a special type of neutron star, the rotating dense remnant of a massive star. Pulsars have highly magnetic surfaces, and emit a beam of electromagnetic radiation […][Read More]
The Daily Campus published an article highlighting the research of Prof. Thomas Blum about Quantum Chromodynamics, a theory which describes the interactions between elementary particles. The development of this theory could help further understanding of the Standard Model of particle physics. The Standard Model is what physicists use to describe the fundamental building blocks of […][Read More]
UConn Astrophysicist and observational astronomer Jonathan Trump was a recent guest on UConn 360, a podcast from the Storrs campus of the University of Connecticut. In this conversation, Jonathan tells about how attending a lecture as an undergraduate at Penn State captured his interest and changed the course of his professional career. Now Jonathan offers […][Read More]
Physicists used to think that superconductivity – electricity flowing without resistance or loss – was an all or nothing phenomenon. But new evidence suggests that it’s not so clear cut, at least in copper oxide superconductors. “If we understood why copper oxide is a superconductor at such high temperatures, we might be able to synthesize a better one”, says UConn physicist Ilya Sochnikov. Sochnikov and his colleagues at Rice University, Brookhaven National Lab and Yale recently figured out part of that puzzle, and they report their results in the latest issue of Nature.[Read More]
Daniel McCarron, assistant professor of physics, the College of Liberal Arts and Sciences, will receive $645,000 over five years for his work on the development of techniques to trap large groups of molecules and cool them to temperatures near absolute zero. The possible control of molecules at this low temperature provides access to new research applications, such as quantum computers that can leverage the laws of quantum mechanics to outperform classical computers.[Read More]
When Carlos Trallero started his academic career in physics, he had no idea he would become a pioneer in a field of research that uses high-power lasers to investigate atomic and molecular physical phenomena. Originally from Cuba, where there isn’t much funding for experimental research, Trallero began his academic career by studying theoretical physics. But as a senior graduate student at Stony Brook University, he got the chance to work in a lab doing experimental work and quickly recognized it was his true passion.[Read More]
May 27-June 5 UConn Physics Department hosted an international summer school Strong interactions beyond simple factorization: collectivity at high energy from initial to final state. The school was supported by an NSF grant to Prof. Kovner and was devoted to modern approaches to the physics of high energy hadronic and heavy ion collisions.[Read More]
Amelia Henkel, graduating Double Major in Physics and Human Rights, and President of the Undergraduate Women in Physics Club, speaks on the CLAS website about her passion for physics and human rights, and how she mastered challenges in her remarkably interdisciplinary curriculum. “We really need to interact with other disciplines,” says Amelia, “because that’s […][Read More]
On April 11th and 12 of 2019 Prof. Paul Corkum of the Joint Attosecond Laboratory (University of Ottawa and the National Research Council of Canada) visited the department. Prof. Corkum’s main area of research is on the interaction of ultrashort laser pulses with matter broadly defined. His most notable contribution is perhaps the discovery of […][Read More]
The University of Connecticut’s Katherine Whitaker is part of a team of astronomers who have put together the largest and most comprehensive “history book” of the universe from 16 years’ worth of observations from NASA’s Hubble Space Telescope.This image, a mosaic of nearly 7,500 separate Hubble exposures, presents a wide portrait of the distant universe and contains roughly 265,000 galaxies that stretch back through 13.3 billion years to just 500 million years after the Big Bang.[Read More]
UConn physics professor Nora Berrah has been elected to the historic and prestigious American Academy of Arts and Sciences. This year, more than 200 individuals were elected to the academy with compelling achievements in academia, business, government, and public affairs. Berrah, who was head of the physics department from 2014 to 2018, has been recognized […][Read More]
This image is the first ever taken of a black hole, captured by the Event Horizon Telescope (EHT) project. The black center is a direct view of the event horizon of a supermassive black hole with a mass of 6.5 billion times the Sun, lying at the center of the Virgo cluster of galaxies. The bright ring is emission from hot gas just above the event horizon, with an asymmetric shape caused by gravitational lensing of light in the strong gravity of the black hole. The EHT collaboration captured the image using a network of 8 radio telescopes that spanned the Earth.[Read More]
An international research team headed by Dr. Aaron LaForge from the research group of Prof. Nora Berrah in the Physics department at UConn has recently discovered a new type of decay mechanism leading to highly efficient double ionization in weakly-bound systems. The team has published its results in the science journal “Nature Physics”. Ionization is […][Read More]
Original UConn Today article here Rising Star in Astrophysics Receives Sloan Foundation Fellowship February 19, 2019 – Jessica McBride – Office of the Vice President for Research Kate Whitaker, assistant professor of physics, stands next to a telescope inside the observatory on top of the Gant Complex on Feb. 14, 2019. (Peter Morenus/UConn Photo) As […][Read More]
Physics professor Nora Berrah has been named a 2018 Fellow of the American Association for the Advancement of Science (AAAS). Prof. Berrah has been recognized for her distinguished contributions to the field of molecular dynamics, particularly for pioneering non-linear science using x-ray lasers and spectroscopy using synchrotron light sources. View full story on CLAS website.[Read More]
A young Cara Battersby once scrawled out the phrase “Science is curious” in a school project about what she wanted to do when she grew up.
This simple phrase still captures Battersby’s outlook on her research about our universe.
Recently shortlisted for the 2018 Nature Research Inspiring Science Award, Battersby has been working on several projects aimed at unfolding some of the most compelling mysteries of galaxies near and far.
“I’m really interested in how stars are born,” Battersby says. “They’re the source of all life on Earth.”
Battersby is leading an international team of over 20 scientists to map the center of the Milky Way Galaxy using the Submillimeter Array in Hawaii, in a large survey called CMZoom. She was recently awarded a National Science Foundation grant to follow-up on this survey and create a 3D computer modeled map of the center of the Milky Way Galaxy.[Read More]
Connor Occhialini – Finalist 2018 LeRoy Apker Undergraduate Achievements Award by Jason Hancock One of our star undergraduates, Connor Occhialini, has won national recognition as a finalist in the 2018 LeRoy Apker Undergraduate Achievements Award competition for his research in the UConn Physics department. The honor and distinction is awarded not only for the excellent […][Read More]
Dr. Antonio Picón, Departamento de Química, Facultad de Ciencias, Universidad Autónoma de Madrid, "Mapping the real-time movies of chemical bonds", Atomic, Molecular, And Optical Physics Seminar4:00pm
Dr. Antonio Picón, Departamento de Química, Facultad de Ciencias, Universidad Autónoma de Madrid, "Mapping the real-time movies of chemical bonds", Atomic, Molecular, And Optical Physics Seminar
Wednesday, March 3rd, 2021
04:00 PM - 05:00 PM
Storrs Campus onlineDr. Antonio Picón, Departamento de Química, Facultad de Ciencias, Universidad Autónoma de Madrid
Mapping the real-time movies of chemical bonds
Valence electrons play a crucial role in the formation of chemical bonds within a molecular system and determine its charge and electron transfer properties. In the static regime, these properties are defined by the electron density distribution of the equilibrium geometry. However, when out of equilibrium, ultrafast electronic rearrangements within the order of a few femtoseconds together a significant alteration of the chemical bonds can occur. I will address in this talk our undergoing investigations for mapping these ultrafast changes through X-ray photoelectron spectroscopy that have been critical in retransforming the well-established concepts of chemical shifts. I will additionally illustrate our developments for the selective manipulation of chemical bonding through X-ray free electron laser pulses.
Dr. Siddharth Mohite, UW-Milwaukee and CCA, Flatiron Institute, "Investigating Populations across the Gravitational-Wave Mass Spectrum: Statistical Tools and Implications for Astrophysics", Astronomy Seminar11:30am
Dr. Siddharth Mohite, UW-Milwaukee and CCA, Flatiron Institute, "Investigating Populations across the Gravitational-Wave Mass Spectrum: Statistical Tools and Implications for Astrophysics", Astronomy Seminar
Wednesday, March 3rd, 2021
11:30 AM - 12:00 PM
Storrs Campus onlineDr. Siddharth Mohite, UW-Milwaukee and CCA, Flatiron Institute
Investigating Populations across the Gravitational-Wave Mass Spectrum: Statistical Tools and Implications for Astrophysics
Merging compact object binaries comprising of pairs of black holes, neutron stars or a neutron star and a black hole are energetic sources of gravitational-wave (GW) and electromagnetic (EM) radiation. Current and future gravitational-wave observatories such as LIGO-Virgo-KAGRA, LISA and NANOGrav will help uncover a diverse population of these binaries across the mass spectrum. While the LIGO-Virgo-KAGRA observatories probe compact objects roughly from 1 to 100 times a solar mass, observatories such as LISA and NANOGrav are predicted to probe supermassive binaries in the million to billion solar mass regimes. On the other hand, telescopes around the world will aid in detecting binaries that contain neutron stars by observing an associated electromagnetic counterpart called a kilonova. Investigating the properties of these binary populations will shed light on some long-standing problems in astrophysics such as stellar and galaxy evolution and nuclear equation of state. In this talk, I will present an attempt to create a Bayesian framework that can simultaneously use information from GW and EM surveys to place constraints on the kilonova population. I will also briefly introduce a method to model the mass distribution of binaries detectable by LIGO-Virgo-KAGRA, using Gaussian processes. Finally, I will also present some investigations into modeling the effects of circum-binary gas and eccentricity on the expected gravitational-wave sources from merging supermassive black hole binaries detectable by observatories like NANOGrav.
Joyce Caliendo, University of Connecticut , "Early Science with the Large Millimeter Telescope: Constraining the Gas Fraction of a Compact Quiescent Galaxy at z = 1.883 ", Astronomy Seminar11:00am
Joyce Caliendo, University of Connecticut , "Early Science with the Large Millimeter Telescope: Constraining the Gas Fraction of a Compact Quiescent Galaxy at z = 1.883 ", Astronomy Seminar
Wednesday, March 3rd, 2021
11:00 AM - 11:30 AM
Storrs Campus onlineJoyce Caliendo, University of Connecticut
Early Science with the Large Millimeter Telescope: Constraining the Gas Fraction of a Compact Quiescent Galaxy at z = 1.883
We present constraints on the dust continuum flux and inferred gas content of a gravitationally lensed massive quiescent galaxy at z=1.883 +/- 0.001 using AzTEC 1.1mm imaging with the Large Millimeter Telescope. MRG-S0851 appears to be a prototypical massive compact quiescent galaxy but has evidence that it experienced a centrally concentrated rejuvenation event in the last 100 Myr. This galaxy is undetected in the AzTEC image but we calculate an upper limit on the millimeter flux and use this to estimate the H_2 mass limit via an empirically calibrated relation that assumes a constant molecular gas-to-dust ratio of 150.
We constrain the 3 sigma upper limit of the H_2 fraction from the dust continuum in MRG-S0851 to be M_(H_2)/M_* < 6.8%. MRG-S0851 has a low gas fraction limit with a moderately low sSFR owing to the recent rejuvenation episode, which together results in a relatively short depletion time of
Dr. H. Larsson, California Institute of Technology, "Molecules in quantum motion --- Understanding electrons, nuclei, and their interactions", Atomic, Molecular, And Optical Physics Seminar4:00pm
Dr. H. Larsson, California Institute of Technology, "Molecules in quantum motion --- Understanding electrons, nuclei, and their interactions", Atomic, Molecular, And Optical Physics Seminar
Monday, March 1st, 2021
04:00 PM - 05:00 PM
Storrs Campus onlineDr. H. Larsson, California Institute of Technology
Molecules in quantum motion ---
Understanding electrons, nuclei, and their interactions
In order to fully understand the chemical physics of molecular systems, we need to simulate both the electronic and vibrational motion quantum mechanically. However, simulations of quantum many-body systems, such as molecules, scale exponentially with system size. I will explain how to tame this 'curse of dimensionality' by combining methods from the traditionally disjoint fields of electronic structure and nuclear dynamics. This combination has enabled the simulation of complex systems with unprecedented accuracy and speed. I will demonstrate how these methods make it possible to solve a diverse set of problems, ranging from characterizing hydrated protons on a molecular quantum level to the interaction of molecules with extremely short and intense light pulses on attosecond time scales. I will demonstrate how these simulations provide new insight into complex fundamental physical processes.
Dr. Jean Marcel Ngoko Djiokap, Department of Physics & Astronomy, University of Nebraska, Lincoln, "Control of Electron Motion on an Attosecond Timescale ", Atomic, Molecular, And Optical Physics Seminar4:00pm
Dr. Jean Marcel Ngoko Djiokap, Department of Physics & Astronomy, University of Nebraska, Lincoln, "Control of Electron Motion on an Attosecond Timescale ", Atomic, Molecular, And Optical Physics Seminar
Wednesday, February 24th, 2021
04:00 PM - 05:00 PM
Storrs Campus onlineDr. Jean Marcel Ngoko Djiokap, Department of Physics & Astronomy, University of Nebraska, Lincoln
Control of Electron Motion on an Attosecond Timescale
Technological advances 20 years ago in producing new extreme ultraviolet coherent light sources with attosecond duration have created a new research field, namely, attosecond physics. A main goal of attosecond physics is to control electron motion on its natural (attosecond) timescale, in order to probe bond formation and breaking in molecules during chemical reactions. A milestone toward achieving such goal is the experimental realization of isolated, few-cycle, attosecond pulses seeded by a free electron laser (FEL) or high harmonic generation (HHG) with stable and tunable carrier-envelope phase (CEP), and with full control of their polarizations. Unlike HHG, X-ray attosecond pulses from FEL have sufficient intensities that permit the realization of the holy grail (atto-pump/atto-probe experiments) of attosecond physics. Use of circularly or elliptically polarized attosecond light opens the possibility of presently investigating and manipulating linear and nonlinear effects that are not accessible with linearly-polarized pulses. In this talk, after briefly introducing the physical mechanisms at the basis of attosecond pulse generation, I will focus on our numerical and analytical methods for the investigation of ultrafast ionization processes in atoms and molecules of astrophysical interest, with emphasis on two-electron processes in which electron correlations play a key role. Enabled by the broad bandwidth of attosecond pulses, the first unusual effect we predicted in double photoionization of H2 by an intense few-cycle elliptically polarized attosecond pulse is the molecular symmetry-mixed dichroism (MSMD. The other effect is the novel electron phenomenon of electron vortices in attosecond photoionization of atoms and molecules, which provides a dramatic example of wave-particle duality. Our predictions of electron matter-wave vortices, which have now been observed experimentally, have already opened a new interdisciplinary area in physics.
Dr. S. Feeney, UCL, "Clarifying the Hubble Constant Tension", Astronomy Seminar11:00am
Wednesday, February 24th, 2021
11:00 AM - 12:00 PM
Storrs Campus onlineDr. S. Feeney, UCL
Clarifying the Hubble Constant Tension
Our best estimate of the Universe's current expansion rate (the Hubble constant) from the local Universe (via the Cepheid distance ladder) is in four-sigma tension with the value extrapolated from cosmic microwave background data assuming the standard cosmology. Whether this discrepancy represents physics beyond the Standard Model or deficiencies in our understanding of the data is the subject of intense debate. In this talk, I will review the community's attempts to explain and interpret the Hubble constant tension, clarifying the current picture using Bayesian probability theory, and consider the potential for independent gravitational wave observations to arbitrate the dispute.
Contact Information: Prof. C. MingarelliMore
Dr. Anh-Thu Le, Missouri University of Science and Technology, "Toward Ultrafast Molecular Imaging with Intense Laser Pulses ", Atomic, Molecular, And Optical Physics Seminar4:00pm
Dr. Anh-Thu Le, Missouri University of Science and Technology, "Toward Ultrafast Molecular Imaging with Intense Laser Pulses ", Atomic, Molecular, And Optical Physics Seminar
Wednesday, February 17th, 2021
04:00 PM - 05:00 PM
Storrs Campus onlineDr. Anh-Thu Le, Missouri University of Science and Technology
Toward Ultrafast Molecular Imaging with Intense Laser Pulses
High harmonic generation (HHG), laser-induced electron diffraction, and other rescattering phenomena are at the heart of strong-field and attosecond physics. However, it is challenging to interpret experimental measurements as accurate ab initio calculations for molecules in intense laser fields are essentially prohibitive. Recently, we developed the quantitative rescattering theory to provide a simple solution to this problem. Our theory establishes direct links between these strongly nonlinear processes with the well-studied traditional scattering processes, thereby making realistic simulations possible. More importantly, our theory allows straightforward decoding of the imprints of the target structure from the experimental data. In this talk, I will present our recent contributions in interpreting different experiments and reconstructing molecular structure for targets that undergo ultrafast transformations. Furthermore, I will also discuss our progress in molecular imaging with ultrafast soft X-ray pulses from HHG or free-electron laser sources. Finally, I will discuss the challenges and our future directions in developing theoretical tools for practical realization of molecular "movies" with atomic resolution in space and time that can provide new insights into fundamental chemical reactions.
Dr. Francois Mauger, Department of Physics & Astronomy, Louisiana State University, " Watching electrons move in molecules", Atomic, Molecular, And Optical Physics Seminar4:00pm
Dr. Francois Mauger, Department of Physics & Astronomy, Louisiana State University, " Watching electrons move in molecules", Atomic, Molecular, And Optical Physics Seminar
Monday, February 15th, 2021
04:00 PM - 05:00 PM
Storrs Campus onlineDr. Francois Mauger, Department of Physics & Astronomy,
Louisiana State University
Watching electrons move in molecules
Electrons are the glue that holds matter together: Their spatial arrangement defines chemical bonds, and their time evolution controls reactions. But electrons are light, and they move fast, reaching down to the femtosecond and attosecond regimes. So probing dynamics at the spatial and temporal scales of electron motions in molecules is a formidable challenge, one that holds the promise of going beyond the "what happened" of spectroscopy to the "how did that happen" that a movie provides. New ultrafast light sources, like X-ray lasers and table-top attosecond sources, together with state-of-the-art theoretical tools are opening this frontier. In this talk I will discuss recent developments and future perspectives for watching coherent electron motion in molecules. This research, at the frontier of ultrafast science, involves cross-disciplinary approaches intersecting atomic and molecular physics and chemistry, optics and lasers, applied mathematics and computer science.
Dr. Kris Pardo, Jet Propulsion Laboratory , "Detecting Gravitational Waves and Dark Matter with the Roman Space Telescope's Exoplanet Microlensing Survey", Astronomy Seminar11:00am
Dr. Kris Pardo, Jet Propulsion Laboratory , "Detecting Gravitational Waves and Dark Matter with the Roman Space Telescope's Exoplanet Microlensing Survey", Astronomy Seminar
Wednesday, February 10th, 2021
11:00 AM - 12:00 PM
Storrs Campus onlineDr. Kris Pardo, Jet Propulsion Laboratory
Detecting Gravitational Waves and Dark Matter with the Roman Space Telescope's Exoplanet Microlensing Survey
The Roman Space Telescope's Exoplanet Microlensing Survey will take tens of thousands of exposures of 10 million stars over 5 years, pinpointing their positions with extreme accuracy. The nominal purpose of this mission is to detect over a thousand planets; however, its unique design and excellent astrometric precision also open other avenues of astrophysical study. Gravitational waves and dark matter halos can both cause apparent changes in stellar positions in a correlated manner. In this talk, I will explain these phenomena and how this survey will let us study supermassive black hole populations and dark matter properties.
WebEx meeting URL: https://uconn-cmr.webex.com/meet/cmf19005
Contact Information: Prof. C. FaesiMore
Dr. A. Stevens, NSF Postdoctoral Fellow, Michigan State University and University of Michigan, "Mapping Matter in Strong Gravity: Spectral-Timing of Black Holes and Neutron Stars ", Astronomy Seminar11:00am
Dr. A. Stevens, NSF Postdoctoral Fellow, Michigan State University and University of Michigan, "Mapping Matter in Strong Gravity: Spectral-Timing of Black Holes and Neutron Stars ", Astronomy Seminar
Wednesday, February 3rd, 2021
11:00 AM - 12:00 PM
Storrs Campus onlineDr. A. Stevens, NSF Postdoctoral Fellow, Michigan State University and University of Michigan
Mapping Matter in Strong Gravity: Spectral-Timing of Black Holes and Neutron Stars
One of the best laboratories to study strong-field gravity is the inner 100s of kilometers around black holes and neutron stars in binary systems with low-mass stars like our Sun. The X-ray light curves of these systems show variability on timescales from milliseconds to months -- the rapid variability can appear as quasi-periodic oscillations (QPOs), which may be produced by general relativistic effects. My research looks at QPOs from black holes and neutron stars by applying state-of-the-art "spectral-timing" techniques to constrain the physical origin of these signals. In this talk, I will discuss data from NICER, an X-ray telescope attached to the International Space Station. I will also highlight open-source astronomy research software and the importance of mental wellbeing in academia.
Webex link: https://uconn-cmr.webex.com/meet/jot16106
Contact Information: Prof. J. TrumpMore
Prof. J. Haraldsen, University of North Florida , "Examining multi-band effects on the electronic compressibility of a 2D electron gas: Insights into the negative compressibility of LAO/STO", Condensed Matter Physics Seminar11:00am
Prof. J. Haraldsen, University of North Florida , "Examining multi-band effects on the electronic compressibility of a 2D electron gas: Insights into the negative compressibility of LAO/STO", Condensed Matter Physics Seminar
Wednesday, February 3rd, 2021
11:00 AM - 12:00 PM
Storrs Campus onlineProf. J. Haraldsen, University of North Florida
Examining multi-band effects on the electronic compressibility of a 2D electron gas: Insights into the negative compressibility of LAO/STO
In this study, we investigate the consequences of two electronic bands at the negative electronic compressibility (NEC) cross-over point for a two-dimensional electron gas (2DEG) using a simple homogeneous model with Coulombic interactions and first-order multi-band coupling. We examine the role of effective mass and relative permittivity in relation to the critical carrier density at the cross-over point through a comparison of one- and two-band models. In general, it is shown that the population of a second band, along with the presence of inter-band coupling, can dramatically change the cross-over carrier density. Given the difficulty in determining and confirming multi-band electronic systems, this model provides a potential method for identifying multi-band electronic systems using precise bulk electronic properties measurements. To help illustrate this method, we apply our results to the observed NEC in the 2D electron gas at the interface of LaAlO3/SrTiO3 (LAO/STO) and determine that, for the known parameters of LAO/STO, the system is likely a realization of a two-band 2D electron gas. Furthermore, we provide general limits on the inter-band coupling with respect to the electronic band population.
Zoom link: https://kth-se.zoom.us/j/62759109592
Prof. P. Mannheim, Department of Physics, University of Connecticut, "Is Dark Matter Fact or Fantasy -- Clues from the Data", Astronomy Seminar11:00am
Prof. P. Mannheim, Department of Physics, University of Connecticut, "Is Dark Matter Fact or Fantasy -- Clues from the Data", Astronomy Seminar
Wednesday, January 27th, 2021
11:00 AM - 12:00 PM
Storrs Campus onlineProf. P. Mannheim,
Department of Physics, University of Connecticut
Is Dark Matter Fact or Fantasy -- Clues from the Data
We discuss arguments both in favor of and against dark matter. With the repeated failure of experiment to date to detect dark matter we discuss what could be done instead, and to this end look for clues in the data themselves. We identify various regularities in galactic rotation curve data that correlate the total gravitational potential with luminous matter rather than dark matter. We identify a contribution to galactic rotation curves coming from the rest of the visible universe, and suggest that dark matter is just an attempt to describe this global effect in terms of standard local Newtonian gravity within galaxies. Thus the missing mass is not missing at all -- it has been hiding in plain sight all along as the rest of the visible mass in the universe.
Webex link: https://uconn-cmr.webex.com/meet/cab16109
Dr. Caitlin Witt, Department of Physics and Astronomy, West Virginia University, Astronomy Seminar10:00am
Wednesday, January 20th, 2021
10:00 AM - 11:00 AM
Storrs Campus onlineDr. Caitlin Witt, Department of Physics and Astronomy, West Virginia University
Multimessenger Astrophysics in the NANOGrav Pulsar Timing Array
Nearly all galaxies contain supermassive black holes, and when these galaxies merge, they can form supermassive black hole binaries. As they progress towards merger, these binaries emit strong nanohertz gravitational waves (GWs). In the next few years, pulsar timing arrays will reach the sensitivities required to detect GWs from both individual supermassive black hole binaries, as well as the stochastic GW background formed by the entire population of these binaries. However, GWs are not the only method used to search for supermassive binaries; by combining GW searches with electromagnetic searches, we enter the regime of multimessenger astrophysics. In this talk, I'll discuss multimessenger efforts within the NANOGrav pulsar timing array, including the recently published targeted multimessenger search for GWs that I led for the collaboration. We developed the first collaboration toolkit for analysis of multimessenger data, and applied it to the well-known binary candidate 3C 66B. We also demonstrated improvements to constraints that can be made by including electromagnetic data in this way. I'll also present some of my ongoing work on the electromagnetic searches for supermassive black hole binaries, where we are exploring the capabilities of binary detection methods on AGN with periodic variability, for both existing and future time-domain surveys.
Webex link: https://uconn-cmr.webex.com/meet/cmf19005
Contact Information: Dr. A. HuangMore
Anahita Alavi, University of California, Riverside, "Dwarf Galaxies Before Exciting Future Observations: The Importance of Extragalactic HST UV Imaging Surveys", Astronomy Seminar12:00pm
Anahita Alavi, University of California, Riverside, "Dwarf Galaxies Before Exciting Future Observations: The Importance of Extragalactic HST UV Imaging Surveys", Astronomy Seminar
Wednesday, December 9th, 2020
12:00 PM - 01:00 PM
Storrs Campus onlineAnahita Alavi, University of California, Riverside
Dwarf Galaxies Before Exciting Future Observations: The Importance of Extragalactic HST UV Imaging Surveys
Dwarf galaxies (M*/M0 < 109) are the smallest and least luminous but most abundant galaxies in the universe. These galaxies are at the forefront of many important questions in galaxy formation theory, yet observationally we are only just beginning to constrain their physical properties, especially at high redshifts. Therefore, it is not surprising that JWST, Roman Telescope, and Euclid will be devoting some part of their time to study these galaxies via their stellar continuum and/or nebular emission lines at various redshifts.
In this talk, I will show how the combination of our deep UV imaging with WFC3/UVIS camera on HST and extensive spectroscopic observations with MOSFIRE spectrograph at the Keck observatory and grism data from WFC3 Infrared Spectroscopic Parallel Survey (WISP) allowed us to 1- observe dwarf galaxies at high redshifts (i.e., 1 (i.e., 1 < z < 3 ), which have always been below the detection limits of many surveys, and 2- better understand the formation and evolution of this population of galaxies via studying their number density evolution (i.e., luminosity function), star formation history (i.e., bursty SFH) and dust attenuation. In addition, I will introduce our new large UV imaging surveys with HST (UVCANDELS and UV Frontier Fields II), which will further explore the high-redshift dwarf galaxies. These UV surveys are vitally important because some of their primary science goals, such as studying the escaping ionizing radiation from galaxies, cannot fundamentally be studied by JWST. Relatedly, I will present our recent work of searching for escaping ionizing radiation from low-mass galaxies at high redshift.
Condensed Matter Physics Seminar10:00am
Tuesday, December 8th, 2020
10:00 AM - 11:00 AM
Storrs Campus onlinePeter Littlewood, University of Chicago
Dynamical phase transitions at many body exceptional point
Spontaneous synchronization is at the core of many natural phenomena. Your heartbeat is maintained because cells contract in a synchronous wave; some bird species synchronize their motion into flocks; quantum synchronization is responsible for laser action and superconductivity. The transition to synchrony, or between states of different patterns of synchrony, is a dynamical phase transition that has much in common with conventional phase transitions of state -- for example solid to liquid, or magnetism -- but the striking feature of driven dynamical systems is that the components are "active". Consequently quantum systems with dissipation and decay are described by non-Hermitian Hamiltonians, and active matter can abandon Newton's third law and have non-reciprocal interactions. This substantially changes the character of many-degree-of-freedom dynamical phase transitions and the critical phenomena in their vicinity, since the critical point is an "exceptional point" where eigenvalues become degenerate and eigenvectors coalesce. We will illustrate this in several different systems -- a Bose-Einstein condensate of polaritons, models of multicomponent active matter such as flocks of birds, generalised Kuramoto models, and others. We argue that there is a systematic theory, generalized phase diagram, and corresponding universality classes for these dynamical systems.
Fruchart et al., arXiv:2003.13176
Hanai et al., 10.1103/PhysRevLett.122.185301
Zoom Meeting: https://kth-se.zoom.us/j/67773156040
Prof. Steven Longmore, Liverpool John Moores University, "Ecosystems and Life", Astronomy Seminar10:00am
Wednesday, December 2nd, 2020
10:00 AM - 11:00 AM
Storrs Campus onlineProf. Steven Longmore, Liverpool John Moores University
Ecosystems and Life
Abstract: I will cover two topics united under the theme of ecosystems shaping the potential for life. In the first half, I will present recent results showing that the architecture of planetary systems is shaped by their environmental ecosystems, in particular the degree of stellar clustering around their host star (Winter et al, 2020, Nature, 586, 528). We identify old, co-moving stellar groups around exoplanet host stars in the astrometric data from the Gaia satellite and demonstrate that the architecture of planetary systems exhibits a strong dependence on local stellar clustering in position-velocity phase space, implying a dependence on their formation or evolution environment. After controlling for host stellar age, mass, metallicity, and distance from the Sun, we obtain highly significant differences in planetary (system) properties between phase space overdensities and the field. The median semi-major axis and orbital period of planets in overdensities are 0.087 au and 9.6 days, respectively, compared to 0.81 au and 154 days for planets around field stars. 'Hot Jupiters' (massive, close-in planets) predominantly exist in stellar phase-space overdensities, strongly suggesting that their extreme orbits originate from environmental perturbations rather than internal migration or planet-planet scattering. Our findings suggest that stellar clustering is an important factor setting the architectures of planetary systems. In the second half of the talk, I will discuss how we are using astrophysics research techniques to help ecologists protect ecosystems, save critically endangered animal species, and stop peat forest fires that are a major contributor to climate change.
Webex link: https://uconn-cmr.webex.com/meet/cab16109
Prof. H.Haggard, Bard College, "Why do so many black holes measured in gravitational waves have zero spin?", Particle, Astrophysics, And Nuclear Physics Seminar2:00pm
Prof. H.Haggard, Bard College, "Why do so many black holes measured in gravitational waves have zero spin?", Particle, Astrophysics, And Nuclear Physics Seminar
Monday, November 30th, 2020
02:00 PM - 03:00 PM
Storrs Campus onlineProf. H.Haggard, Bard College
Why do so many black holes measured in gravitational waves have zero spin?
Black hole entropy is a robust prediction of quantum gravity with no established phenomenological consequences to date. We use the Bekenstein-Hawking entropy formula and general-relativistic statistical mechanics to determine the probability distribution of random geometries uniformly sampled in phase space. We show that this statistics (in the limit \( \hbar \to 0\) ) is relevant to large curvature perturbations, resulting in a population of primordial black holes with zero natal spin. In principle, the identification of such a population at LIGO, Virgo, and future gravitational wave observatories could provide the first observational evidence for the statistical nature of black hole entropy.
Prof. Sang Wook Cheong, Department of Physics and Astronomy, Rutgers University, "Trompe L'oeil Ferromagnetism", Condensed Matter Physics Seminar9:30am
Prof. Sang Wook Cheong, Department of Physics and Astronomy, Rutgers University, "Trompe L'oeil Ferromagnetism", Condensed Matter Physics Seminar
Monday, November 30th, 2020
09:30 AM - 10:30 AM
Storrs Campus onlineProf. Sang Wook Cheong,
Department of Physics and Astronomy, Rutgers University
Trompe L'oeil Ferromagnetism
The characteristics of ferro-(ferri)magnetism with non-zero magnetization include magnetic attraction, magnetic circular dichroism, and magneto-optical Kerr (MOKE), Faraday, and various anomalous Hall-type (Hall, Ettingshausen, Nernst, and thermal Hall) effects. Non-magnetic or antiferromagnetic materials in external electric fields or other environments (called specimen constituents) can share symmetry operational similarity (SOS) with magnetization in relation to broken symmetries. These specimen constituents can be associated with non-zero magnetization and/or show ferromagnetism-like behaviors, so we say that they exhibit Trompe L'oeil Ferromagnetism. Examples include linear magnetoelectric materials such as Cr2O3 under electric fields, Faraday effect in chiral materials such as tellurium with current flow, magnetic field induced by the motion of Neel- or Bloch-type ferroelectric walls, and magneto-optical Kerr (MOKE), Faraday effect, and/or anomalous Hall-type effects in certain antiferromagnets such as Cr2O3, MnPSe3, Mn4(Nb,Ta)2O9, and Mn3(Sn,Ge,Ga). A large number of new specimen constitutes having SOS with Magnetization will be discussed, and require future experimental verification of their ferromagnetism-like behaviors, and also theoretical understanding of possible microscopic mechanisms.
We will have two presentations and by Los Alamos theorists:, Condensed Matter Physics Seminar9:30am
Tuesday, November 24th, 2020
09:30 AM - 11:00 AM
Storrs Campus onlineWe 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
Dr. Vivienne Baldassare, Washington State Univeristy , "Searching for active galactic nuclei in low-mass galaxies via optical variability", Astronomy Seminar11:00am
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 onlineDr. 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
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
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 onlineProfessor 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.
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
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
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 onlineMohammad 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
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 onlineProf 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.
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
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 onlineDr. 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
Contact Information: Prof. K. JooMore
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
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 onlineDr. 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:
Meeting ID: 819 264 8596
Note: The seminar will start at 2:00PM, but participants are welcomed to join the meeting at 1:30PM for discussion.
Dr. D. Farfurnik, University of Maryland, "Enhancing the coherence properties of quantum dots toward quantum photonic applications", Condensed Matter Physics Seminar10:00am
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 onlineDr. 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 . 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 , 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 . 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 .
 D. Farfurnik et al., ``Optimizing a dynamical decoupling protocol for solid-state electronic spin ensembles in diamond'', Phys. Rev. B 92, 060301(R) (2015)
 J.H. Bodey et al., ``Optical spin locking of a solid-state qubit'', npj Quantum Information 5, 95 (2019)
 D. Kim et al., ``Ultrafast optical control of entanglement between two quantum-dot spins'', Nat. Phys. 7, 223--229 (2011)
 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
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
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 onlineProf. 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,
Zoom Meeting: https://kth-se.zoom.us/j/123036826
Dr. Raffaella DeVita, INFN Genoa and Jefferson Lab, "Hadron spectroscopy in the light quark sector", Particle, Astrophysics, and Nuclear Physics Seminar2:00pm
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-413EDr. 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
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-413EProf. Masafumi Fukuma, Kyoto University
CANCELLED:, Dr. J. Nathan Hohman, Institute of Materials Science and the Department of Chemistry, University of Connecticut, CANCELLED: Condensed Matter Physics Seminar2:00pm
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 119CANCELLED:
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.
Contact Information: Prof. B. WellsMore
Dr. Sumanta Bandyopadhyay, Nordita, "Superconductivity in a nonhermitian system and Berezinksii classification ", Condensed Matter Physics Seminar2:00pm
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 119Dr. Sumanta Bandyopadhyay,
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  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
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 119CANCELLED:
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  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 . 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 .
Recently, our theoretical prediction of the stability of high-PT bcc Fe phase [1,4] was confirmed by diamond anvil cell experiments . 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.
 A. B. Belonoshko, T. Lukinov, J. Fu, J. Zhao, S. Davis, S. I. Simak Nature Geoscience 10, 312 (2017).
 A. B. Belonoshko, J. Fu, T. Bryk, S. I. Simak, M. Mattesini, Nature Communications 10, 1-7 (2019).
 A. B. Belonoshko, R. Ahuja, B. Johansson, Nature 424, 1032 (2003).
 R. Hrubiak, Y. Meng, G. Shen, arXiv:1804.05109 Experimental evidence of a body centered cubic iron at the Earth's core conditions.