Dr. Taran Driver, PULSE institute and SLAC National Accelerator Laboratory and Linac Coherent Light Source

Probing Correlated Multi-Electron Dynamics on the Attosecond Timescale

The interaction of light with matter is a fundamental process for probing and engineering the quantum properties of a molecule or material. This interaction is mediated by electrons, and understanding the many-body dynamics of electronic systems in the first moments following light-driven excitation is a frontier challenge. The characteristic timescale for this electron motion is set by the splitting of the relevant energy levels, which results in motion on the attosecond (10-18 s) timescale. It is now possible to generate pulses of light lasting on the order of one hundred attoseconds, both on the tabletop in the laboratory and at large free-electron laser facilities. I will present recent work using attosecond x-ray pulses to probe the ultrafast dynamics of multi-electron systems. We measured the photoemission delay in the core-level ionization of a molecule. This is the delay between the arrival of a photon and the emission of an electron in photoionization, which was long considered an instantaneous process. In fact, this delay reveals strong modulations due to electron correlation. We also time-resolved the response of an aromatic molecule, para-aminophenol, to impulsive photoionization. By accessing the dynamics within the first femtosecond following the removal of an electron, we observed the interplay between the sub-femtosecond decay of shake-up states and coherent charge density oscillation on the few-femtosecond timescale. I will also touch on future directions which will harness these new methods to develop ultrafast probes of electron motion and exotic light-engineered states in quantum materials.

Prof. Lina Necib, Department of Physics, MIT

Mapping out the Dark Matter in the Milky Way

In this talk, I will explore the interfacing of simulations, observations, and machine learning techniques to construct a detailed map of Dark Matter in the Milky Way, focusing on the Galactic Center/Halo and dwarf galaxies. For the Galactic Halo, I will present a recent work that reveals a decline in the stellar circular velocity, inducing tensions with established estimates of the Milky Way’s mass and Dark Matter content. I will discuss how the underestimated systematic errors in such a common methodology necessitates a revised approach that combines theory, observations, and machine learning. In dwarf galaxies, I will present a novel Graph Neural Network methodology that facilitates the accurate extraction of Dark Matter density profiles, validated against realistic simulations. I will conclude with a discussion on the future trajectory of astroparticle physics, emphasizing the need for the integration of astrophysical probes with experimental Dark Matter research, potentially leading to a better understanding of the nature of Dark Matter.

Prof. Philip Mannheim, Department of Physics, University of Connecticut

Why there are dark matter, dark energy, and quantum gravity problems, and what we can do about them

We trace the origin of the dark matter, dark energy and quantum gravity problems to the extrapolation of the standard Newton-Einstein wisdom to beyond its solar system origins. We show that this same solar system wisdom can be obtained from the conformal gravity theory, with its extrapolation leading to a resolution of all of the dark matter, dark energy and quantum gravity problems.

Prof. Vernon Cormier, Department of Physics, University of Connecticut

Physics of Earth’s Core

Among the terrestrial planets, Earth has the largest magnetic field, driven by convective motion in an electrically conducing iron rich liquid outer core.  This field has been sustained since nearly the time of Earth’s formation, preventing loss of water and atmospheric erosion by the solar wind.  Research to understand the evolution and dynamics of the core includes measurements and modeling of its gravitational and magnetic fields, the propagation of elastic waves sampling its interior, and the theories of condensed matter physics.  Outstanding problems include the unknown light element composition of the outer and inner cores, the crystalline lattice structure of the solid inner core and that of iron at 360 GPa and 6000 deg. K, gravitational and electromagnetic coupling between Earth’s mantle and solid inner core, the low shear modulus and Poisson’s ratio of the inner core, and the possibility of the inner core being in a superionic state.

Dr. Yu He, Yale University

Electronic pseudogap from fluctuations in low dimensional materials

Most metal-to-insulator and metal-to-superconductor transitions are so dramatic that certain symmetries are also concurrently broken, and an energy gap opens in lockstep with this process. But there are electronic systems that develop energy gaps without any broken symmetry, most notably the “pseudogap” in cuprate superconductors. In this talk, I will show two examples of electronic pseudogap in unexpected places: the heavily hole-doped cuprates [1], and an excitonic insulator candidate Ta2NiSe5 [2]. The former is supposedly a good metal where mean-field BCS is thought to apply, and the latter is a structural symmetry-breaking system with strong electron-phonon coupling. Via angle-resolved photoemission spectroscopy and x-ray scattering, we show the electronic gap to persist well above the transition temperature in both systems. With insights from controlled numerical calculations, we show that fluctuation is an important factor when describing the properties of low dimensional material systems. Finally, I will discuss a few new directions in the study of fluctuations.

[1] Phys Rev X 11, 031068 (2021); Nat Mater 22, 671 (2023)

[2] Phys Rev Research 5, 043089 (2023); Nat Commun 14, 7512 (2023)

Adam Riess- Bloomberg Distinguished Professor and 2011 co-winner of the Nobel Prize in Physics, Johns Hopkins University

In 1929 Edwin Hubble discovered that our Universe is expanding. Eighty years later, the Space Telescope that bears his name is being used to study an even more surprising phenomenon: that the expansion is speeding up. The origin of this effect is not known, but is broadly attributed to a type of “dark energy” first posited to exist by Albert Einstein and now dominating the mass-energy budget of the Universe. Professor Riess will describe how his team discovered the acceleration of the Universe and why understanding the nature of dark energy presents one of the greatest remaining challenges in astrophysics and cosmology. He will also discuss recent evidence that the Universe continues to defy our best efforts to predict its behavior.

Adam Riess is a Bloomberg Distinguished Professor, the Thomas J. Barber Professor in Space Studies at the Krieger School of Arts and Sciences, a distinguished astronomer at the Space Telescope Science Institute and a member of the National Academy of Sciences.

He received his bachelor’s degree in physics from the Massachusetts Institute of Technology in 1992 and his PhD from Harvard University in 1996. His research involves measurements of the cosmological framework with supernovae (exploding stars) and Cepheids (pulsating stars). Currently, he leads the SHOES Team in efforts to improve the measurement of the Hubble Constant and the Higher-z Team to find and measure the most distant type Ia supernovae known to probe the origin of cosmic acceleration.

In 2011, he was named a co-winner of the Nobel Prize in Physics and was awarded the Albert Einstein Medal for his leadership in the High-z Supernova Search Team’s discovery that the expansion rate of the universe is accelerating, a phenomenon widely attributed to a mysterious, unexplained “dark energy” filling the universe. The discovery was named by Science magazine in 1998 as “the Breakthrough Discovery of the Year.”

His accomplishments have been recognized with a number of other awards, including a MacArthur Fellowship in 2008, the Gruber Foundation Cosmology Prize in 2007 (shared), and the Shaw Prize in Astronomy in 2006.

Reception at 3:00pm in the Gant Science Light Court

Madisyn Brooks, UConn

Title and abstract TBA

Prof. Andrew Puckett, Department of Physics, University of Connecticut

Precision studies of proton and neutron structure via medium-energy electron scattering

Electron scattering has been one of the most important tools for precisely probing the femtoscopic structure of strongly interacting matter ever since Hofstadter’s pioneering measurements of electron-proton scattering and electron-nucleus scattering at Stanford in the 1950s revealed the non-point-like nature of the proton and provided a first direct measurement of the proton’s size, leading to the Nobel Prize in Physics in 1961. The Continuous Electron Beam Accelerator Facility (CEBAF) at Jefferson Lab (JLab) in Newport News, Virginia, is the world’s leading facility for the precision three-dimensional imaging of the nucleon’s quark-gluon structure in both coordinate and momentum space. CEBAF uses superconducting radio-frequency acceleration technology to deliver electron beams of unparalleled quality in terms of energy, intensity, duty-cycle, and polarization. Experimentalists use these high-quality electron beams together with state-of-the-art target and detector technologies and high-performance data acquisition and computing capabilities to map the internal structure of strongly interacting matter with unprecedented precision and kinematic reach. In this talk, I will give a brief overview of the physics of electron scattering and its utility as a precision probe of nuclear structure, followed by a detailed overview of UConn’s role and Ph.D. research opportunities at JLab with the Puckett group.

Dr. Shafique Adam, Washington University in St. Louis

A narrow magic window for ultraflat bands and emergent heavy fermions near the magic angle in twisted bilayer graphene

The notion of a single “magic angle” in twisted bilayer graphene has evolved into a fascinating array of magic angles and ranges each describing different facets of the material’s behavior.  While the original continuum model predicted a nominal magic angle, its simplicity ignored the intricate interplay of different physical phenomena.  For example, lattice relaxation [1] near the magic angle shifts its value upward, only to be counteracted by pseudomagnetic fields.  Including a symmetry allowed relaxation parameter changes this magic angle to a magic range.  Yet another magic angle emerges from the coupling to phonons when the Fermi velocity equals the phonon sound velocity.  Building upon this rich tapestry of magical effects, we will discuss our recent work on the convergence of lattice relaxation and Hartree interaction near the magic angle [2]. We unveil a previously unreported Lifshitz transition to a Fermi surface topology that supports a “heavy fermion” pocket and an ultraflat band pinned to the Fermi energy. Analytical and numerical insights shed light on the narrow “magic angle range” where the “heavy fermion” is stable and make predictions for its experimental observation.  We believe that the bands presented here are accurate  at high temperature and provide a good starting point to understand the myriad of complex behavior observed in this system.

[1] “Analytical Model for Atomic Relaxation in Twisted Moiré Materials” by MMA Ezzi, GN Pallewela, C De Beule, EJ Mele, and S Adam, arXiv:2401.00498 (2024)

[2] “A self-consistent Hartree theory for lattice-relaxed magic-angle twisted bilayer graphene” by MMA Ezzi, L Peng, Z Liu, JHZ Chao, GN Pallewela, D Foo, and S Adam arXiv:2404.17638 (2024)

Prof. Luca Argenti, University of Central Florida

ASTRA: A Transition-Density-Matrix Approach to Time-Resolved Molecular Ionization

Attosecond science, which investigates the time-resolved correlated motion of electrons in atoms, molecules, and solids, is rapidly advancing toward larger molecular systems and more complex processes, such as multiple ionization and molecular fragmentation. Theoretical methods capable of addressing both multiple excitations and photofragment entanglement are essential to capture these phenomena. Among the most promising theoretical approaches are ab initio wave-function-based close-coupling (CC) methods, increasingly adopted by the AMO community.

Despite significant progress from codes like XCHEM [1,2], tRecX [3], RMT [4], and UKRmol+ [5], scaling remains a major challenge – whether in handling ionic correlation, accounting for many atoms, or for distant fragments. To address these limitations, we developed ASTRA [6] (AttoSecond TRAnsitions), an ab initio CC molecular ionization code based on high-order transition density matrices between correlated ionic states of arbitrary multiplicity [7], and hybrid Gaussian-B-spline integrals [5,9]. ASTRA integrates multiple state-of-the-art codes, such as DALTON [8], a general-purpose quantum chemistry code, LUCIA [7], a large-scale CI code, and GBTOlib [5], a hybrid integral library suited for slow photoelectrons and comparatively small molecules.

ASTRA has successfully reproduced total and partial photoionization cross sections, photoemission asymmetry parameters, and molecular-frame photoelectron angular distributions for molecules such as N ₂ , CO, H ₂ CO, and Pyrazine, showing excellent agreement with existing benchmarks. Currently, ASTRA is being applied to study attosecond transient absorption spectra of CO and O ₂ , as well as sequential XUV-pump IR-probe ionization of C ₂ H ₄ . Its formalism naturally extends to molecular double ionization and can efficiently model electron exchange between multiple disjoint molecular fragments − relevant for describing ionization in weakly bound clusters like (H ₂ O) _n .

Looking ahead, continued integration with tools tailored to high-energy photoemission, non-adiabatic nuclear dynamics, and strong fields ionization will be critical for addressing emerging challenges in ultrafast many-body dynamics. Free-electron lasers enable time-resolved studies of core ionization, while table-top attosecond pump-probe experiments are targeting increasingly larger molecules, monitoring both electron dynamics and nuclear rearrangements throughout chemical reactions with intense probe pulses [10]. To reproduce these complex experiments, we are collaborating with NIST to replace GBTOlib with a more efficient hybrid library capable of handling larger molecules and higher orbital angular momenta. We are also pairing ASTRA with surface-hopping methods [11], where multiphoton ionization is typically not available. Additionally, to track the asymptotic evolution of weakly coupled photofragments under strong light fields − without incurring prohibitive computational costs − we are considering integrating separate optimized propagators for each fragment, which will open the door for us to simulate strong-field multichannel molecular-ionization processes.

[1] M. Klinker et al., J. Phys. Chem. Lett. 9, 756 (2018).

[2] V. J. Borràs et al., Science Advances 9, eade3855 (2023).

[3] A. Scrinzi, Comput. Phys. Commun. 270, 108146 (2022).

[4] A. C. Brown et al., Comput. Phys. Commun. 250, 107062 (2020).

[5] Z. Masin et al., Comp. Phys. Commun. 249, 107092 (2020).

[6] J. M. Randazzo et al., Phys. Rev. Res. 5, 043115 (2023).

[7] J. Olsen et al., J. Chem. Phys. 89, 2185 (1988); ibid. 104, 8007 (1996).

[8] K. Aidas et al., Comp. Mol. Sci. 4, 269 (2014).

[9] H. Gharibnejad et al., Comp. Phys. Commun. 263, 107889 (2021).

[10] F. Vismarra et al., Nature Chemistry (2024).

[11] L. Fransén et al., J. Phys. Chem. A 128, 1457 (2024).

Prof. Philip Mannheim, University of Connecticut

The Accelerating Universe

I will describe some of the background that led to the award of the Nobel prize to Dr. Adam Riess, who will be our 2024 Katzenstein speaker on November 15.

Dr. Jakob den Brok, Harvard Smithsonian Center for Astrophysics

Title and abstract TBA

Prof. Anh-Thu Le, Department of Physics, University of Connecticut

Following electron-nuclear dynamics with ultrafast intense lasers

Recent progress in laser technology has led to new coherent light sources that can be used to investigate ultrafast processes in matter. To take advantage of these new light sources, different experimental techniques have been developed to reveal the inner-workings of coupled electron-nuclear dynamics in molecules. Concurrently, theoretical and computational tools have also been developed to understand and decode hidden information from experimental measurements. In this talk, I will present our group’s recent progress in understanding intense laser-atom/molecule interactions by using some of the most promising techniques such as laser-induced electron diffraction, high-harmonic generation spectroscopy, and attosecond transient absorption spectroscopy. I will also address the challenges and opportunities in this field for practical realization of molecular “movies” with atomic resolution in space and time that can provide new insights into fundamental chemical reactions.

Prof. Matthew Guthrie, University of Connecticut;

A New Era for Connecticut’s Oldest Planetarium: Historic Roots to Modern Revival

The UConn Planetarium, built in 1954, has long been a central resource for astronomy education and outreach at the University of Connecticut. In this talk, I will present an overview of the planetarium’s historical roots at UConn, its significance in the community, and the extensive renovations we have completed to bring this important facility back to life. After years of disuse, the planetarium has been fully upgraded with modern technology and will officially reopen on November 1st, immediately following this colloquium.

Our efforts to restore the planetarium are guided by the legacy of Dr. Cynthia Peterson, UConn’s first woman physics faculty member and a pioneer in science education. The planetarium now officially bears her name as the Cynthia Wyeth Peterson Memorial Planetarium, in honor of her decades of dedication to astronomy outreach. Following my presentation, Nora Berrah and Celeste Peterson will speak about Dr. Peterson’s life and achievements - how her contributions to UConn and the wider scientific community continue to resonate today.

Prof. Moshe Gai, Department of Physics, University of Connecticut

Concepts of Stellar Evolution

Star are born, they evolve to a mature midlife and sooner or later die, some in an amazing last display. We will discuss how star reveal the stages of Stellar Evolution and what makes them tick. We will also seek feedback on the need for such a graduate class at UConn.

Prof. Philip Kim, Harvard University

Searching for Anyon in Quantum Materials

The search for anyons, quasiparticles with fractional charge and exotic exchange statistics, has inspired decades of condensed matter research. Moreover, it has been predicted that exchange braiding of these particles, especially non-abelian anyons, can produce topologically protected logic operations that can serve as building blocks for fault-tolerant quantum computing. In this talk, I will discuss the progress of research on two quantum materials platforms to realize these exotic particles. In the first example, we will discuss anyons arising in fractional quantum Hall (FQH) effects, using quantum Hall interferometers for direct observation of the anyon braiding phase around a confined cavity. In the second example, we will discuss our recent experimental efforts to realize non-abelian anyons in proximitized topological insulator surfaces by controlled manipulation of magnetic vortices containing non-abelian anyons.

Jacob Heeren, Collins Aerospace

Skill sets for data science positions in industry

Webex URL: https://uconn-cmr.webex.com/meet/drl20003

Jacob Heeren is a data analyst at Collins Aerospace, where he supports both commercial and military operations. His responsibilities span the entire data pipeline, encompassing data engineering, visualization, analytics, and governance across diverse projects. He holds degrees in psychology and applied mathematics from Iowa State University, with additional studies in astrophysics at the University of Iowa. Outside of his professional role, Jacob enjoys rock climbing and creating music, reflecting his passion for both physical and creative pursuits. Jacob will discuss his career path, current role, and useful skill sets for data science positions

Profs. Xian Wu and Erin Scanlon and Matt Guthrie, 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. 

Prof. Jun Ye, University of Colorado and JILA

Title and abstract TBA

Román Fernández Aranda, Department of Physics, University of Crete and FORTH Institute of Astrophysics, Greece

A Burning Hot DOG: The extreme ISM conditions of the most luminous obscured galaxy in The Universe

Hot dust-obscured galaxies (or Hot DOGs) are a remarkable population of high-redshift galaxies. Hot DOGs harbor hyper-luminous supermassive black holes (SMBHs), which are believed to provide strong feedback, creating extreme conditions in the interstellar medium (ISM) of their host galaxies in recurrent episodes of strong accretion and heavy obscuration. W2246-0526 is a Hot DOG at redshift 4.6 and the most luminous obscured galaxy known to date. I will present ALMA observations of both the brightest far-IR fine-structure emission lines and their underlying dust continuum, combined with ISM modeling of the gas and the dust. This work sheds light on the extreme conditions galaxies can experience during the early stages of the Universe, which is critical to our understanding of how distant and young galaxies evolve.

Prof. Shohini Bhattacharya, Department of Physics, University of Connecticut

Exploring the Cosmic Core of Nucleons with the Electron-Ion Collider

Have you ever wondered what holds the universe together at its most fundamental level? The answer lies in Quantum Chromodynamics (QCD), the theory that describes how quarks and gluons—collectively known as partons—interact to form nucleons, the protons and neutrons that make up all visible matter. Despite our understanding of QCD, the inner workings of partons remain one of the most profound mysteries in physics. How do they move? How do they contribute to a nucleon’s spin and structure? The Electron-Ion Collider (EIC), a cutting-edge facility soon to be operational, is poised to address these profound questions. In this talk, I will take you on a journey into the “cosmic core” of nucleons and explain how the EIC, like a super-powered microscope, will enable us to peer deep inside protons and neutrons, unveiling the dynamics of partons. I will focus on one of my key research projects aimed at unraveling the nucleon spin puzzle using the capabilities of the EIC. But the excitement doesn’t end there. Advancing our understanding of QCD not only helps us probe nucleons but also allows us to test the Standard Model of particle physics, our most comprehensive theory of the universe. Together, we will explore the far-reaching implications of this research field.

Prof. Bryce Gadway, Penn State

Synthetic Dimensions in Rydberg Atom Array

Arrays of dipolar-interacting spins - magnetic atoms, polar molecules, and Rydberg atoms - represent powerful and versatile platforms for analog quantum simulation experiments. The internal state dynamics in these dipolar arrays provide a natural setting to explore problems of equilibrium and non-equilibrium quantum magnetism. The presence of many internal states of the atoms and molecules further enables studies of large-spin magnetism, but also holds promise for more general quantum simulation studies. Here we describe how the simple addition of multi-frequency microwave fields to Rydberg arrays enables highly controllable studies of few- and many-body dynamics along an internal-state “synthetic” dimension. I’ll discuss several early studies in the Rydberg synthetic dimension platform, touching on interaction-driven phenomena relevant to topology, artificial gauge fields, and disorder-induced localization. Looking forward, such microwave manipulation opens up several new directions for exploring complex, driven quantum matter in dipolar arrays.

Dr. Tien Tien Yeh, NORDITA and UConn

Structured Light and Induced Vorticity in Superconductors

Questions of controlling the quantum states of matter via light have been at the forefront of research on driven phases. We demonstrate the effects of imprinted vorticity on superconducting coherent states using structured light. Within the framework of the generalized time-dependent Ginzburg-Landau equation, we show the induction of coherent vortex pairs moving in phase with electromagnetic wave oscillation. The structured light, generated by a Laguerre-Gaussian beam, provides light sources with various quantum properties, such as spin angular momentum and orbital angular momentum. This state of light is also well known as an optical vortex, characterized by a twisted phase front. In the current work, we investigate the optically induced dynamics of superconducting coherent states using both normal light sources and optical vortices. These results uncover rich hydrodynamics of superconducting states and suggest new optical applications for imprinting quantum states on superconducting materials.

Prof. Lea Ferreira dos Santos, Department of Physics, University of Connecticut

Nonequilibrium Quantum Dynamics

Santos’s group uses numerical and analytical methods to understand, predict, and control the dynamics of quantum systems taken far from equilibrium. This talk will present two lines of research of the group. (i) The characterization of quantum systems with many interacting particles, the timescales for their relaxation process, and the conditions for reaching thermal equilibrium. (ii) The use of the quantum-classical correspondence to better understand and make use of static and dynamical properties of transmon qubits, which are the predominant element in circuit-based quantum information processing.

Prof. Wenchao Ge, University of Rhode Island

How to Make a Faster Trapped-Ion Quantum Computer?

Trapped ions offer a pristine platform for quantum computation, but enhancing the interactions without compromising the qubits remains a crucial challenge. In this talk, I will present a strategy to enhance the interaction strengths in trapped-ion systems via parametric amplification of the ions’ motion, thereby suppressing the relative importance of decoherence. We illustrate the power of this approach by showing how it can improve the speed and fidelity of two-qubit gates in multi-ion systems and how it can enhance collective spin states useful for quantum metrology. Our proposal has been further demonstrated in the experiment, confirming the enhancement. Our results open a new avenue of phonon modulation in trapped ions and are directly relevant to numerous other physical platforms in which spin interactions are mediated by bosons.

Prof. Peter Schweitzer, Department of Physics, University of Connecticut

Internal Structure of Hadrons

Hadrons are composed particles and exhibit a rich internal structure which is probed experimentally in high energy experiments and described in the theory of Quantum Chromodynamics. Recent advances in the theory of hadron structure with focus on gravitational form factors are discussed.

Dr. Eric Koch, Harvard Smithsonian Center for Astrophysics

Revealing the multi-phase neutral interstellar medium’s role in the star formation lifecycle: a sharpened view of nearby galaxies from LGLBS and PHANGS-JWST

The neutral interstellar medium (ISM) fuels the star formation lifecycle, yet we still lack vital constraints on the formation and destruction of molecular clouds because of challenges in observing the cold neutral ISM phases with high resolution and sensitivity. With dedicated surveys, the combination of VLA, ALMA, and JWST can now make significant advances in the coming years. In this talk, I will present multiple observational approaches that are making progress in this area: detailed 21-cm HI VLA mapping across the Local Group from the Local Group L-band Survey (lglbs.org), resolved molecular cloud studies with ALMA and JWST in M33 and PAH imaging from PHANGS-JWST as a highly sensitive resolved view of the total neutral gas tracer (phangs.org). These surveys bridge Galactic with extragalactic star formation studies and provide new constraints to guide the next generation of numerical simulations.

The Physics Department ice cream social

will take place on Friday, September 27th at 1:30 in Gant South 117.

All are welcome!

Prof. Simone Colombo, Department of Physics, University of Connecticut

Observing our Universe with Quantum Sensors

In this seminar, we will introduce the application of atomic, molecular, and optical (known as AMO) physics to the field of quantum metrology. We will show how atoms are used as probes of our universe and how to harness quantum effects to enhance their sensing capabilities.

We will then focus on a specific type of atomic sensor and one of our research interests: optical atomic clocks. Building upon recent results, we will illustrate how optical clocks’ performances can be pushed beyond current limitations and how they can be/are deployed to get a better glimpse of the inner workings of our universes. In this framework, we will highlight the research activities that we are currently pursuing in our lab. Crucially, we will attempt to give a perspective on the life of an AMO physicist.

Prof. Nikolay Prokofiev, UMass Amherst

Bi-polaron superconductivity in the low density limit

It has been assumed for decades that high values of Tc from the electron-phonon coupling are impossible. At weak-to-intermediate coupling strength this result follows from the Migdal-Eliashberg theory, while at strong coupling, when bipolarons form, the transition temperatures are low because of the exponential effective mass enhancement. However, the latter conclusion was based on numerical solutions of the Holstein model. I will discuss a different model with coupling based on the displacement modulated hopping of electrons and argue that much larger values of the bipolaron Tc can be achieved in this setup. Non-locality of the problem gives rise to small-size, yet relatively light bipolarons, which can be studied by an exact sign-problem-free quantum Monte Carlo approach even in the presence of strong Hubbard and Coulomb potentials. We find that Tc in this model generically and significantly exceeds typical upper bounds based on Migdal-Eliashberg theory or superfluidity of Holstein bipolarons, and, thus, offers a route towards the design of high-Tc superconductors via functional material engineering. Finally, there are indications for even better prospects in systems with non-linear electron-phonon coupling.

Jake Lewitt, Cortex Fusion, New York, NY

Nuclear fusion in molecules using lasers

Cortex Fusion Systems, Inc. uses shaped ultrafast laser pulses to catalyze fusion reactions in molecules. Our work comprises (1) designing transiently confining effective one-electron potentials in field-dressed molecules, (2) performing quantum chemistry calculations to validate the enhancement of nuclear tunneling by laser-modified electron screening dynamics, and (3) testing pulse shapes in the laser lab by coupling ultrafast spectroscopy techniques with nuclear radiation detection and spectrometry. In this regard, “quantum-controlled fusion” is a coherent, under-the-barrier process that does not require plasma ignition. Our goal is to repurpose the modern suite of commercial femtosecond laser amplifiers and pulse-shaping techniques to achieve compact and scalable fusion generators using quantum control.

Prof. Mingda Li, Nuclear Science and Engineering, MIT

Exploring Potential Roles of Machine Learning in Quantum Materials Research

In recent years, machine learning has achieved great success in chemistry and materials science, but quantum materials face unique challenges. These include the scarcity of data (volume challenge), high dimensionality and computational costs (complexity challenge), elusive experimental signatures (experimental challenge), and unreliable ground truth (validation challenge).

In this Physics Colloquium, we present our recent efforts to support the study of quantum materials with machine learning. For scenarios with high data volumes, such as density-functional-theory (DFT) level studies with weak correlation, machine learning can predict lower-dimensional properties. We introduce a convolutional neural network classifier predicting band topology class based on X-ray absorption (XAS) signals [1]. This approach can also be applied to experimental data, demonstrated by an autoencoder-based protocol to study the magnetic proximity effect with polarized neutron reflectometry, improving fitting resolution [2].

For lower data volumes due to higher computational costs, incorporating symmetry into neural networks can reduce data volume needs. Using the O(3) Euclidean neural network, we predict phonon density-of-states [3], dielectric functions [4], and quantum weight [5] directly from crystal structures. Machine learning without data can also be performed by using differential equations as constraints [5].

For high output dimensions and low input data volumes, such as phonon dispersion relations, we introduce additional approaches like virtual nodes in a graph neural network [6], showing improved efficiency compared to machine-learning potential without losing accuracy.

To address unreliable ground truth, we use machine learning to distinguish Majorana zero modes in scanning tunneling spectroscopy for topological quantum computation [7]. For cases like quantum spin liquids, where experimental signatures are unclear and computational costs are high, we generate materials with potential geometrical frustration. Our latest work, SCIGEN, produces eight million materials belonging to Archimedean lattices, with over 50% passing DFT stability checks after pre-screening [8].

Despite progress, applying machine learning to quantum materials is still in its infancy. We reflect on the out-of-distribution problem, aiming to generate genuine surprises and new features rather than merely recognizing patterns. Additionally, we must address accuracy limitations in many machine learning approaches, especially with complex quantum systems and phase diagram studies.

[1] “Machine learning spectral indicators of topology,” Advanced Materials 34, 202204113 (2022).

[2] “Elucidating proximity magnetism through polarized neutron reflectometry and machine learning,” Applied Physics Review 9, 011421 (2022).

[3] “Direct prediction of phonon density of states with Euclidean neural networks,” Advanced Science 8, 2004214 (2021).

[4] “Ensemble-Embedding Graph Neural Network for Direct Prediction of Optical Spectra from Crystal Structure,” arXiv:2406.16654.

[5] “Panoramic mapping of phonon transport from ultrafast electron diffraction and machine learning,” Advanced Materials 35, 2206997 (2023).

[6] “Virtual Node Graph Neural Network for Full Phonon Prediction,” Nature Computational Science 4, 522 (2024).

[7] “Machine Learning Detection of Majorana Zero Modes from Zero Bias Peak Measurements,” Matter 7, 2507 (2024).

[8] “Structural Constraint Integration in Generative Model for Discovery of Quantum Material Candidates,” arXiv:2407.04557.

Monica Vidaurri, Stanford University and NASA Goddard

Ethics and Aliens: the need for an ethical approach to space science

The progress of space science and exploration has seemingly inevitably fallen to private companies, to the concern of private citizens and scientists, who are directly impacted by private actions in space. Additionally, academia has reached a critical limit in terms of unchecked features that promote elitism and exclusionism, including increasingly competitive admissions to programs and fellowships, scarcity in jobs, prevalent sexual harassment, and others. As individuals, it is difficult to imagine what a truly ethical framework for our work looks like, let alone how we alone can influence laws and policy to change the actions of individuals with seemingly unlimited wealth and resources. This talk will introduce 3 main facets of what ethics means with respect to space science and exploration, including introducing space science as a historically oppressive institution, and how we can begin to move past this as individuals, labs, departments, and institutions. The norms we allow and ignore ultimately shape these broader laws, policies, and workplace culture. As a result, our science cannot be detached from the social and political framework it exists in, and the custom of early and regular collaboration with ethicists and planetary protection specialists (and other social scientists) is critical for not only mission safety, but mission and science integrity, as well as the well-being of those contributing to the mission and who gets to be included in such work. Creating a safe, responsible, and ethical space for peaceful purposes cannot wait for the international space community to create these practices de jure, but must be started at the individual level and regarded as custom for integration into international law, de facto, and require an uncomfortable self-assessment in the true goals of space science, as well as the ways that the academic structure has failed certain groups of students. By creating a new framework that prioritizes ethics, only then can we responsibly go into the unknown.

Everyone is welcome to attend (undergraduate and graduate students, staff, and faculty at the physics department). This big event is part of our efforts to foster a welcoming work environment and solidify our physics community. 

Dr. Guochao Sun, Northwestern University

Unveiling the Physics of Galaxy Formation and its Large-Scale Effects at Cosmic Dawn

Cosmic Dawn, loosely defined here to be the first billion years of cosmic time, is an ever-intriguing era that witnessed the formation of the first generations of galaxies. Toward the end of it there was also the last major phase transition of our Universe, the epoch of reionization (EoR), which is believed to be driven by the hydrogen-ionizing background emerged from the early galaxies formed. In this talk, I will explain how Cosmic Dawn becomes a real exciting epoch for unveiling the physics of galaxy formation thanks to the James Webb Space Telescope (JWST), as well as several forthcoming facilities such as SPHEREx, Roman Space Telescope, Square Kilometer Array, and LiteBIRD focusing on the large-scale effects. I will discuss the theoretical landscape galaxy formation at Cosmic Dawn informed by new JWST observations, with a particular focus on the phenomenon of bursty star formation. I will introduce methods and ideas to shed light on different aspects of early galaxy formation, including the star formation history, stellar feedback, outflows, and the ionizing output, using both individual galaxies and their effects on the large-scale structure and cosmic background radiations. With a few case studies, I will demonstrate how to harness the power of the aforementioned facilities and their synergies for these purposes.

Prof. Cara Battersby, Department of Physics, University of Connecticut

The Milky Way Laboratory

Galaxy centers are the hubs of activity that drive galaxy evolution, from supermassive black holes to feedback from dense stellar clusters. While the bulk of our Milky Way Galaxy is a prime example of present epoch “normal” star formation, our galaxy’s center has gas properties that are more reminiscent of star formation during its cosmic peak. In our research group, the Milky Way Laboratory, we capitalize on both the “normal” and “extreme” star formation in our own cosmic backyard in order to resolve the interplay of physical processes in detail. In this talk, I will discuss efforts to measure how stars gain their mass and how the star formation process may vary across the Galaxy. In our galaxy’s central molecular zone, the process of star formation is complicated by constant gas inflow, high levels of turbulence, and more. I will present both simulations and observations toward this region that aim to understand the role of the gas inflow, the 3-D geometry of the region, properties of the gas, and incipient star formation.

Grad student town hall

Prof. Carlos Trallero, Department of Physics, University of Connecticut

Quantum times

The uncertainty principle for a free electron provides one of the most fundamental time scales known as the Coulomb time scale, that ranges from 3 to 8 zeptoseconds (10-21s). I will discuss about experimental developments in our lab with this temporal resolution and it’s application to fundamental measurements as well as applied research.

Welcome back to UConn Astro!

Dr. Zeyang Li, Stanford University

Applying Cavity QED to Quantum Information Science

Abstract TBA

Dr. Sebastian Schenk, University of Mainz

Quantum Imprint of the Anharmonic Oscillator

We discuss the anharmonic oscillator in quantum mechanics using exact WKB methods in a ‘t Hooft-like double scaling limit where classical behavior is expected to dominate. We compute the tunneling action in this double scaling limit, and compare it to the transition amplitude from the vacuum to a highly excited state. Our results, exact in the semiclassical limit, show that the two expressions coincide, apart from an irreducible and surprising instanton contribution. The semiclassical limit of the anharmonic oscillator betrays its quantum origin as a rule showing that the quantum theory is intrinsically gapped from classical behavior. Besides an example of a resurgent connection between perturbative and nonperturbative physics, this may provide a way to study transition amplitudes from tunnelling actions, and vice versa.

Note the special room: GS 413E

Graduate student Debadarshini Mishra, Department of Physics, University of Connecticut

Photo-Induced Ultrafast Dynamics in Molecules

Imaging electronic and molecular dynamics at ultrafast timescales is crucial for understanding the mechanisms of chemical reactions, which are of fundamental importance in fields ranging from materials science to biochemistry. Furthermore, gaining insights into these processes at the atomic and molecular levels can enable precise control over reaction dynamics, leading to significant technological advancements through the development of efficient catalysts, innovative materials, and targeted drugs. In this dissertation talk, I will present my work on imaging time-resolved dynamics in molecular systems, using various light sources and ultrafast spectroscopy techniques. First, I will discuss a method for the direct visualization of neutral fragments in roaming reactions, which involve an unconventional dissociation process, using coincident Coulomb explosion imaging. Next, I will explore ultrafast electron diffraction as a different yet complementary imaging technique to identify the competing non-radiative relaxation pathways for a UV-excited molecule. Finally, I will briefly discuss our recent work on relaxation and fragmentation dynamics in large molecules, particularly C60, and isomerization and excited-state dynamics in small molecules.

Prof.. Reina Maruyama,Yale University

What is dark matter?

Astrophysical observations give overwhelming evidence for the existence of dark matter. Several theoretical particles have been proposed as dark matter candidates, including weakly interacting massive particles (WIMPs), axions, and, more recently, their much lighter counterparts. However, there has yet to be a definitive detection of dark matter. For years, one group, the DAMA collaboration, has asserted that they observe a dark matter-induced annual modulation signal in their NaI(Tl)-based detectors. Their observations are inconsistent with those from other direct detection dark matter experiments under most assumptions of dark matter. In this talk, I will describe how I came to work on this topic and the debate’s current status, the worldwide experimental effort to test this extraordinary claim, and our progress toward resolving the current stalemate in the field.

Note: The pre-colloquium reception will be 3-4pm in the Gant Light Court

Graduate student Mitchell Bredice, Department of Physics, University of Connecticut

Kinetics, Nucleation, and Relaxation Dynamics of Ion-Seeded Nanoparticles

The recent interest in studying the adsorption and emission spectra of the hazy atmospheres of exoplanets stimulates the interest in clusters, small aggregates of atoms or molecules. The nucleation and dynamics of nanoparticles in the Earth’s atmosphere and their impact on the global climate and environment is another important area of research stimulating investigations of nucleation processes. However, how these small aggregates form is not wholly understood. Traditionally, nucleation of clusters or other phases is described through Classical Nucleation Theory. Although this theory has many discrepancies in describing the nucleation of submicron particles. In this work, we have performed molecular dynamics simulations of the nucleation of ion-seeded nanoparticles, specifically ArnH+ clusters, to investigate the microscopic mechanisms of nucleation from a gas or liquid phase. From these simulations, we have studied the stages of the nonequilibrium and equilibrium growth of ArnH+ clusters and analyzed the size distribution and internal energy relaxation of nascent clusters during different stages of their growth. The fundamental impact of the internal energy relaxation on the nonequilibrium nucleation of small ArnH+ clusters has been demonstrated. This analysis has generally been avoided in previous investigations due to assumptions of the equilibrium nature of the nucleation process. The results of our simulations showed that nanoparticles are formed in highly excited states, thus the cluster growth and relaxation are concurrent processes, and that relaxation of the cluster internal energy can delay cluster growth processes. To further investigate the internal energy relaxation, an ensemble of molecular dynamics simulations was performed for the detailed analysis of the average time evolution of kinetic, potential, and total energies of small ArnH+ clusters, and their kinetic energy relaxation. The results of the performed simulations have been explained through the use of a collisional Boltzmann equation describing the energy relaxation processes. Lastly, the general relationship between nonequilibrium growth and internal energy relaxation is discussed.

Prof. Cassandra Paul (San Jose State University)

Title and abstract (TBD)

Contact: Prof. Erin Scanlon

Remote talk (details forthcoming)

Dr. Esteban Goetz, Department of Physics, University of Connecticut

Interferometric Harmonic Spectroscopy for Electron Dynamics Imaging and Attosecond Pulse Train Phase Characterization

The advent of ultrashort light pulses has opened the possibility of investigating atomic and molecular processes on their natural time scales. In particular, Attosecond Transient Absorption Spectroscopy (ATAS) [1], a technique that allows to time-resolve the quantum dynamics of electrons by monitoring the absorption of extreme ultraviolet (XUV) radiation by an atomic or molecular system when the latter is dressed by an infrared (IR) laser source.

Motivated by recent experimental advances in self-referenced interferometric harmonic spectroscopy [2], we theoretically investigate an alternative approach to ATAS for electron dynamics imaging and attosecond pulse train (APT) phase characterization. In contrast to ATAS, which gives access to the imaginary part of the refractive index through an absorption measurement, an interferometric phase measurement gives information of its real part. In this talk, I will discuss the link between the XUV phase measurements of Ref. [2] and the different photoexcitation pathways occurring at the atomic level which are imprinted in the real part of the macroscopic refractive index. As an application, we show how such an interferometric approach can be used for phase retrieval of attosecond pulse trains based on two-arm harmonic spectroscopy and an optimization algorithm. Finally, I will highlight the impact of spin-orbit couplings and macroscopic and field propagation effects on the phase measurements and APT phase retrieval. Our theoretical description is based on numerical solution of the scalar Maxwell equations beyond Beer’s Law for the macroscopic field propagation coupled to the time-dependent Schroedinger equation for the quantum dynamics.

[1] M. Holler et al., Phys. Rev. Lett. 106, 123601 (2011)

[2] G. R. Harrison et al., arXiv:2305.17263 (2023)

Prof. Claudio Chamon, Boston University

Circuit complexity and functionality: a thermodynamic perspective

We explore a link between complexity and physics for circuits of given functionality. Taking advantage of the connection between circuit counting problems and the derivation of ensembles in statistical mechanics, we tie the entropy of circuits of a given functionality and fixed number of gates to circuit complexity. We use thermodynamic relations to connect the quantity analogous to the equilibrium temperature to the exponent describing the exponential growth of the number of distinct functionalities as a function of complexity. This connection is intimately related to the finite compressibility of typical circuits. Finally, we use the thermodynamic approach to formulate a framework for the obfuscation of programs of arbitrary length – an important problem in cryptography – as thermalization through recursive mixing of neighboring sections of a circuit, which can viewed as the mixing of two containers with “gases of gates”. This recursive process equilibrates the average complexity and leads to the saturation of the circuit entropy, while preserving functionality of the overall circuit. The thermodynamic arguments hinge on ergodicity in the space of circuits which we conjecture is limited to disconnected ergodic sectors due to fragmentation. The notion of fragmentation has important implications for the problem of circuit obfuscation as it implies that there are circuits with same size and functionality that cannot be connected via local moves. Furthermore, we argue that fragmentation is unavoidable unless the complexity classes NP and coNP coincide.

Community event for viewing the April 8 solar eclipse, hosted by UConn faculty and students.

90% of the Sun will be eclipsed from our location at maximum 3:25pm

Activities include:

• solar telescopes
• pinhole camera installation, and camera-making demos
• eclipse demos
• eclipse-viewing glasses for sale(fundraisers for undergrad + graduate physics organizations) 

TITLE:

Quantum acoustics and the physics of the strange metals

ABSTRACT:

Quantum acoustics is the analog of quantum optics, with phonons playing the role of photons. The classical fields (electromagnetic, acoustic) are reached by virtue of coherent states in both cases. Quantum acoustics leads to two time dependent, interacting wave fields, one lattice, one quantum. The electron diffuses at a Planckian rate, independent of electron-lattice coupling and temperature, and the calculated resistivity is linear in temperature. Mott-Ioffe-Regel and Drude peak mysteries are also resolved. A rather different carrier transport scenario emerges for the strange metals.

Dr. Paul M. Eugenio, University of Connecticut

Tunable moire sublattices in twisted square homobilayers: exploiting fundamental principles for new technologies

Stacking and twisting atomically thin bilayers at small angles produces an approximate periodic pattern, due to the overlap of the crystal layers. These devices, dubbed “moire” bilayers, exhibit a high degree of tunability and variability: through choice of twist angle, constituent layers, and gating. To date, a number of such devices have been built which have demonstrated a plethora of novel phases, including non-trivial topology and Mott physics. Despite this explosion in moire research, moire bilayers have been almost exclusively formed from layers with triangular/hexagonal crystal geometry, and where the valence bands are centered on the Gamma or K/K’ high symmetry points. Here we theoretically demonstrate that moire devices formed from square bilayers can be used to simulate the ground state of the Hubbard model, but where the ratio of the nearest-neighbor (t) and next-to-nearest neighbor (t’) tunneling can be tuned between zero and infinity, in situ via an electric field. If experimentally realized, such a device would be the first of its kind, and would open a pathway toward the testing of a number of proposed exotic phases, such as a spin-liquid and d+id superconductivity. Most importantly, the square Hubbard model is a quintessential model for high-Tc in cuprates, where numerics has demonstrated the absence of superconductivity when t’=0.

Graduate student Geoff Harrison, Department of Physics, University of Connecticut

ITAS: A Technique for Complete Quantum Measurements on a New Timescale

Transient absorption spectroscopy is a well-established technique used to study electron dynamics in atomic and molecular systems but typically can only measure the magnitude of the electronic wavefunction. We have integrated interferometric methods into this technique to allow complete quantum measurements of both the magnitude and phase of electronic wavefunctions. A spatial light modulator (SLM) is used to separate the interferometric arms in an extremely stable way, enabling the measurement of effects on the zeptosecond timescale (with a jitter of 3zs). In this talk, I’ll describe how we’ve utilized SLMs to make these measurements possible and share some initial data we’ve taken looking at phase effects in argon.

Dr. Fatma Aslan, Jefferson National Laboratory and UConn

Hadron structure-oriented approach to TMD phenomenology

We present a first practical implementation of a recently proposed hadron structure oriented (HSO) approach to TMD phenomenology applied to Drell-Yan like processes. We compare and contrast general features of our methodology with other common practices and emphasize the improvements derived from our approach that we view as essential for applications where extracting details of nonperturbative transverse hadron structure is a major goal. These include the HSO’s preservation of a basic TMD parton-model-like framework even while accounting for full TMD factorization and evolution, explicit preservation of the integral relationship between TMD and collinear PDFs, and the ability to meaningfully compare different theoretical models of nonperturbative TMD parton distributions.

Dr. Nick Hutzler, California Institute of Technology

UConn Physics Colloquium

Title and abstract: TBD

Contact: Profs. Tom Blum and Dan McCarron

Dr. J. I. A. Li, Brown University

The Superconducting Diode Effect And Spontaneous Symmetry Breaking In Multi-Layer Graphene

The superconducting diode effect, defined as nonreciprocity in the critical supercurrent, provides a unique window into the nature of the superconducting phase. It has been argued that a zero-field diode effect in the superconducting transport requires inversion and time-reversal symmetries to be simultaneously broken. Along this vein, the zero-field superconducting diode effect in multi-layer graphene provides direct evidence of the microscopic coexistence between superconductivity and time-reversal symmetry breaking. In this talk, I will discuss our recent efforts that utilize the angle-resolved measurement of transport nonreciprocity to directly probe the nature of spontaneous symmetry breaking in the normal phase. By investigating the interplay between transport nonreciprocity, ferromagnetism, and superconductivity, our findings suggest that the exchange-driven instability in the momentum space plays a key role in the zero-field superconducting diode effect.

Title: A comprehensive insight into nucleons at the Electron-Ion Collider

Abstract:
Quantum Chromodynamics (QCD) is the theory governing the strong interactions that bind quarks and gluons, collectively known as partons, to form nucleons - the fundamental building blocks of visible matter. Achieving a profound understanding of the partonic structure of nucleons stands as a crucial milestone, and the forthcoming Electron-Ion Collider (EIC) at the Brookhaven National Laboratory is poised to be the ultimate tool in nuclear physics for this purpose. In this talk, I will explore a few of my research endeavors, aiming to address key questions such as, “How can we measure the orbital motion of partons within nucleons?” and “How can we uncover quantum anomalies in the distributions of partons within nucleons, and what can we learn from them?” The state-of-the-art theory discussed in this talk plays a pivotal role in providing comprehensive insight into nucleons, exploring the origins of spin, mass, and symmetry breakings - all of which form the bedrock of QCD and the EIC.

Graduate student Debadarshini Mishra, Department of Physics, University of Connecticut

Imaging ultrafast dynamics in molecular systems

Imaging electronic and molecular dynamics at the attosecond and femtosecond timescales is crucial for understanding the mechanisms of chemical reactions, a fundamental aspect in fields ranging from materials science to biochemistry. This in-depth understanding of chemical processes may allow for precise control over reaction dynamics, thereby paving the way for advancements in technology and medicine, for example, by guiding the development of efficient catalysis, innovative materials, and targeted drugs. In this talk, I will describe our work on imaging time-resolved molecular dynamics using two distinct and complementary techniques.

In the first part of my talk, I will discuss the use of coincident Coulomb explosion imaging for the direct visualization of roaming reactions. These reactions represent unconventional pathways that allow fragments to remain weakly bonded, leading to the formation of unexpected final products. Typically, the neutral character of the roaming fragment and its indeterminate trajectory make direct experimental identification challenging. However, I will demonstrate that by leveraging the power of coincidence imaging, we can reconstruct the momentum vector of the neutral roamer and thus identify an unambiguous signature for roaming.

In the second part of my talk, I will discuss the imaging of UV-induced ring-opening and dissociation dynamics using ultrafast electron diffraction. I will demonstrate that by harnessing the superior temporal and structural resolution of this technique, we can explore the competition among different molecular pathways as well as their wavelength-dependent behavior.

Dr. Andrey Tarasov, North Carolina State University

Title: Hadron as a many-body parton system: from parton interactions to non-perturbative phenomena

Due to the phenomenon of confinement, the hadron cannot be understood as a compound state of independent quarks and gluons but rather represents a strongly bounded many-body parton system. The dynamics of this system gives rise to such fundamental properties of the hadron as spin and mass. How the spin and mass of the hadron arise from the parton dynamics is an outstanding question of modern nuclear science. The parton dynamics can be probed in high-energy scattering experiments using the factorization approach. However, there is a wide class of observables that cannot be described within the conventional factorization schemes due to various reasons, including non-perturbative phenomena. In my talk, I will give several concrete examples and propose a solution based on applying the background field techniques, which provide a unified treatment of parton interactions. I will argue that the application of such techniques allows us to obtain a complete picture of the multi-parton dynamics in QCD and shed light on the origin of the proton spin and mass.

Dr. James Cryan, SLAC National Lab (UConn Physics Colloquium)

Ultrafast dynamics using X-ray attosecond pulses.

Contact: Prof. Nora Berrah

Prof. Moshe Gai and Grad. Student Deran Schweitzer, Department of Physics, University of Connecticut

Stellar Evolution: Supernovae

Dr. Adam Freese, Jefferson Lab

Title: Relativistic mass densities: from the light front to generalized parton distributions

Abstract: The dynamical generation of mass is one of the most fascinating aspects of quantum chromodynamics. Partonic imaging allows us to probe where this generated mass is, and to break it down into contributions from quarks and gluons. In particular, imaging gives us access to generalized parton distributions, which provide a relativistic three-dimensional picture of the proton’s internal structure, in terms of two spatial dimensions and a momentum faction x. In this talk, I examine how the light front provides a means of rigorously describing spatial distributions for relativistic systems (such as the proton), how the energy-momentum tensor provides distributions of energy and momentum, and how x-weighted moments of generalized parton distributions give us the most promising empirical means of accessing the mass distribution in the proton. I will review challenges in empirically accessing the GPDs, as well as ongoing efforts to address these challenges.

Prof. Jed Pixley, Rutgers University

Novel Strongly Correlated Phases in Stacked TMD Bilayers

Two-dimensional transition metal dichalcogenides (TMDs) have emerged as an exciting platform to stack and twist bilayers to engineer strongly correlated quantum phases. Here we present a theory to describe the recent realization of a heavy fermion state in stacked MoTe2/WSe2 bilayers. An extension of this theory that allows for the formation of unconventional superconductivity through repulsive nearest neighbor interactions will be used to show how to realize the p-wave BEC to BCS transition.

Dr. Wenliang Li, Stony Brook University

Title: Probing Proton’s Identity using the Electron-Ion Collider

Abstract:

The Electron-Ion Collider, being constructed at the Brookhaven National Lab, is the “dream machine” for nuclear physics studies for the upcoming decades. The diverse capability in the accelerator design offers physicists a unique opportunity to study quark and gluon structures within nucleons and nuclei. Furthermore, the production and detection of the rare isotopes is a possibility.

In this seminar, we will dive into two examples of many creative ways to use the EIC. 1. Probing the proton’s identity (baryon number), and determining who carries the baryon number within its wavefunction: gluon? quark? Both? 2. EIC can collide the electron beam on an ion beam with any atomic mass, could we use it to create and study the rare isotope (via eA collision) to complement the low-energy studies at FRIB?

Dr. Jaspreet Singh Randhawa, Los Alamos National Laboratory

Title: Nuclear reaction studies to decode the observations from neutron stars in binary systems

Abstract: Neutron stars are ideal astrophysical laboratories to test theories of dense matter physics as they may exhibit most exotic forms of matter, and are pivotal in driving nucleosynthesis in various explosive astrophysical environments; e.g X-ray binaries, neutron star mergers. Breath-taking multi-messenger observations of explosive astronomical events are generating exciting new challenges for nuclear physics and force a rethinking of old paradigms. For X-ray binaries, surface nuclear burning proceeds through extremely proton-rich nuclei powering the X-ray bursts, whereas in neutron star mergers nucleosynthesis proceeds through very neutron-rich nuclei. Therefore, to understand the energy generation and nucleosynthesis in these extreme environments, new nuclear data on very exotic nuclei is required, e.g. nuclear reaction rates or detailed nuclear structure/properties of exotic nuclei. Facility for Rare Isotope Beams (FRIB), a newly developed world’s leading radioactive ion beam facility, will provide an unprecedented access to the very exotic proton-rich and neutron-rich nuclei. In this talk, I will highlight the need for new nuclear physics data to decode observations from X-ray binaries and neutron star mergers, and how FRIB is opening up a new window to explore the most exotic nuclei on earth, to provide much-needed data to facilitate model-observation comparison of various astrophysical environments. I will present the new results from on-going reaction studies at FRIB, and will discuss planned measurements, which will help us to answer some of the most important questions in nuclear astrophysics.

Dr. Riccardo Longo, University of Illinois Urbana-Champaign

Title: Probing Hot & Cold QCD Phenomena Using Jets

Abstract:

The LHC Heavy Ion program offers unique opportunities to study Quantum Chromodynamics (QCD) phenomena at various length and temperature scales. In particular, dijets are fantastic probes for exploring emergent QCD properties in different regimes. Hadronic Pb+Pb collisions create a hot and dense medium composed of quarks and gluons, the Quark Gluon Plasma (QGP). Dijets produced by a hard-scattering can be used to investigate the microscopic properties of this nearly perfect fluid. Conversely, measuring dijets in p+Pb collisions allows for studying different proton size configurations and cold nuclear effects that modify the nucleon Parton Distribution Functions (PDFs) when bound into atomic nuclei. Studies to inform nuclear PDF (nPDF) parametrization can also be carried out by analyzing dijets produced in photo-nuclear events, allowing for investigating a unique kinematic regime. Other aspects of the nucleon structure, such as its spin composition, are studied at CERN fixed target experiments by performing polarized DIS and Drell-Yan measurements. In my talk, I will discuss selected aspects of hot and cold QCD addressed by the ATLAS Heavy Ion and COMPASS experiment programs. In particular, I will present recent dijet measurements in p+Pb and Pb+Pb collisions at ATLAS and recent COMPASS polarized Semi-Inclusive DIS and Drell-Yan results.

Finally, I will show how the cold QCD effort will naturally continue in the research avenues that the Electron-Ion Collider will open.

Dr. François Légaré, Institut national de la recherche scientifique, Energy Materials Télécommunications center

Ultrafast IR/mid-IR laser technologies and their applications at ALLS

The Advanced Laser Light Source (ALLS) is a unique user facility located at INRS-EMT (Varennes, Canada) counting on 40M CDN$ of investment since 2002. Since 2019, this facility has jointed the LaserNetUS network and is now funded as a national research infrastructure by the Canada Foundation for Innovation – Major Science Initiatives. These fundings ease access to the facility for academic and government users. In the first part of my talk, I will give an overview of the facility’s capabilities including the most powerful laser in Canada with 750 TW. In the second part, I will discuss novel approaches developed by my team for the generation of ultrashort pulses in the IR and mid-IR spectral range. This includes multidimensional solitary states in hollow core fibers [1,2] as well as using the frequency domain optical parametric amplification for the generation of tunable CEP stable mid-IR laser pulses [3,4]. Pulse characterization in the mid-IR spectral range will be presented [5]. Finally, I will present recent results on the generation of high-dose MeV electrons from tight focussing in air [6].

References

[1] R. Safaei, G. Fan, O. Kwon, K. Légaré, P. Lassonde, B. E. Schmidt, H. Ibrahim, and F. Légaré (2020), High-energy multidimensional solitary states in hollow core fiber, Nature Phot. 14, 733-739.

[2] L. Arias, A. Longa, G. Jargot, A. Pomerleau, P. Lassonde, G. Fan, R. Safaei, P. Corkum, F. Boschini, H. Ibrahim, and F. Légaré, Few-cycle Yb laser source at 20 kHz using multidimensional solitary states in hollow-core fibers, Opt. Lett. 47, 3612-3615 (2022).

[3] A. Leblanc, G. Dalla-Barba, P. Lassonde, A. Laramée, B. Schmidt, E. Cormier, H. Ibrahim, and F. Légaré (2020), High-field mid-infrared pulses derived from frequency domain optical parametric amplification, Opt. Lett. 45, 2267-2270.

[4] G. Dalla-Barba, G. Jargot, P. Lassonde, S. Tóth, E. Haddad, F. Boschini, J. Delagnes, A. Leblanc, H. Ibrahim, E. Cormier, and F. Légaré, Mid-infrared frequency domain optical parametric amplifier, Opt. Express 31, 14954-14964 (2023).

[5] A. Leblanc, P. Lassonde, S. Petit, J.-C. Delagnes, E. Haddad, G. Ernotte, M. R. Bionta, V. Gruson, B. E. Schmidt, H. Ibrahim, E. Cormier, and F. Légaré (2019), Phase-matching-free pulse retrieval based on transient absorption in solids, Opt. Express 27, 28998.

[6] S. Vallières, J. Powell, T. Connell, M. Evans, M. Lytova, F. Fillion-Gourdeau, S. Fourmaux, S. Payeur, P. Lassonde, S. MacLean, and F. Légaré, High Dose-Rate MeV Electron Beam from a Tightly-Focused Femtosecond IR Laser in Ambient Air (2024), Laser Photonics Rev. 18, 2300078.

François Légaré is a chemical physicist who specializes in developing novel approaches for ultrafast science and technologies, as well as biomedical imaging with nonlinear optics (Ph.D. in chemistry, 2004 – co-supervised by Profs. André D. Bandrauk and Paul B. Corkum). Full professor (2013 - …) at the Energy Materials Telecommunications center of the Institut national de la recherche scientifique (INRS-EMT), he was the director of the Advanced Laser Light Source (ALLS) until 2023. Since 2022, he is the director of the INRS-EMT center and CEO of ALLS. Under his scientific leadership, INRS has received in 2017 a grant of 13.9M CDN$ from the Canada Foundation for Innovation and the Quebec government, with 11.9M CDN$ to upscale the ALLS facility with high average power Ytterbium laser systems and advanced instrumentation for time-resolved material characterization. He is a Fellow and senior member of OPTICA and Fellow of the American Physical Society. He is a member of The College of New Scholars, Artists and Scientists of the Royal Society of Canada (2017). He was awarded the Herzberg medal from the Canadian Association of Physics in 2015 and the Rutherford Memorial Medal in physics of the Royal Society of Canada in 2016. He has contributed to about 200 articles in peer reviewed journals including prestigious ones such as Nature, Science, Nature Photonics, Nature Physics, Nature Communications, and Physical Review Letters. According to Google Scholar, his h-index is 59 with more than 13,000 citations.

UConn Physics Colloquium: Dr. Andrew Held

High Power Commercial Laser Markets and Applications

Abstract: Ubiquitous and familiar applications for lasers include telecom data transmission, laser surgery (LASIK), information processing (DVD/Blue Ray), supermarket scanners, laser pointers and a multitude of laser sensing applications (LIDAR, range finders, facial recognition, etc.). Sophisticated laser technology is also well-recognized as a key, enabling research tool.

Perhaps less well known are the “unsung” commercial applications and markets for higher power lasers. Often out of public view, these laser applications drive diverse and massive commercial markets and are supported by extensive industry-based research and development investments. And are generating increasingly abundant STEM based career opportunities.

The presentation will highlight the laser technologies and applications used in materials processing to mark, engrave, cut, and join everything from shoe leather to sheet metal. Also covered are laser applications supporting the manufacturing of microelectronics-based consumer technology, enabling higher performing devices and ever larger displays. The laser technology and developments that support emerging Directed Energy military applications will be also be reviewed.

Bio:

Andrew Held has recently retired as Senior Vice President of Coherent’ s Aerospace and Defense business. Andrew has over 30 years’ experience in General Business Management, Research, Sales and Marketing of lasers and photonics into a broad range of markets and applications. He received his B.S. in Chemistry and Ph.D. in Laser Spectroscopy from the University of Pittsburgh and was an Alexander von Humboldt Research Fellow at the Technical University in Munich.

Prof. Alexander Balatsky, Department of Physics, University of Connecticut

Dynamics and Quantum Sensing: magnetism, gravity and q-bit sensors

Dr. Thomas Weinacht, Stony Brook University

Long Lived Electronic Coherences in Molecules

I will discuss experiments and calculations that demonstrate long lived electronic coherences in molecules using a combination of measurements with shaped octave spanning ultrafast laser pulses, 3D velocity map imaging and calculations of the light matter interaction. Our pump-probe measurements prepare and interrogate entangled nuclear-electronic wave packets whose electronic phase remains well defined despite vibrational motion along many degrees of freedom. The experiments and calculations illustrate how coherences between excited electronic states survive even when coherence with the ground state is lost, and may have important implications for light harvesting, electronic transport and attosecond science.

Dr. Josiah Sinclair, MIT

A new platform for quantum science: programmable arrays of single atoms inside an optical cavity.

Recently, programmable arrays of single atoms have emerged as a leading platform for quantum computing and simulation with experiments demonstrating control over hundreds of atoms [1]. Interfacing an atom array with a high-quality optical cavity promises even greater control and new capabilities. By coupling atoms to an optical cavity, we can more efficiently collect light from each atom improving detection. In addition, an optical cavity can be used to efficiently entangle many atoms in a single step relying on a novel technique called counterfactual carving [2]. I will describe our progress towards the goal of detecting and correcting errors on a register of Rubidium atoms selectively coupled to a large-waist optical cavity. Beyond detecting errors, applying corrections requires real-time feedback, and I will present a simple experiment demonstrating that fast feedback on microsecond timescales can already improve measurement fidelity. Finally, I will describe our accidental realization that we can use our cavity to directly observe collisions between pairs of trapped atoms in real time.

Dr. Yossathorn Tawabutr, University of Jyväskylä

Fully Consistent NLO Calculation of Forward Single-Inclusive Hadron Production in Proton-Nucleus Collisions

We study the single-inclusive particle production from proton-nucleus collisions in the dilute-dense framework of the color glass condensate (CGC) at next-to-leading order (NLO) accuracy. In this regime, the cross section factorizes into hard impact factors and dipole-target scattering amplitude describing the eikonal interaction of the partons in the target color field. For the first time, we combine the NLO impact factors with the dipole amplitude evolved consistently using the NLO Balitsky-Kovchegov (BK) equation with the initial conditions fitted to HERA structure function data.

The resulting neutral pion cross section with all parton channels included are qualitatively consistent with the recent LHCb measurement. In particular, the NLO evolution coupled to the leading order impact factor is shown to produce a large Cronin peak that is not visible in the data, demonstrating the importance of consistently including NLO corrections to all the ingredients. Furthermore, the transverse momentum spectrum is found to be sensitive to the resummation scheme and the running coupling prescription in the BK evolution. This demonstrates how additional constraints for the initial condition of the BK evolution can be obtained from global analyses including both the HERA and LHC data. In light of the upcoming upgrades to the LHC, the dependence of our results on rapidity will also be discussed.

Dr. Jim Zickefoose and Dr. Gabriela Ilie, Senior Scientists, Physics Division, Mirion Technologies, Meriden CT

Mirion Technologies – Connecting Academia and Industry

Mirion Technologies is a world leader in the development and supply of nuclear instrumentation and supporting software. To accomplish its goals and objectives, Mirion has a diverse team of physicists holding various levels of degrees. In this seminar we will show our paths from graduate studies to joining Mirion, emphasizing how the skills we gained during our academic journeys have contributed or have been beneficial to our professional development in industry. Furthermore, we will highlight Mirion Technologies’ general areas of interest as well as revealing some interesting applications where we have partnered with academia.

Speakers’ bio:

Gabriela is the Product Line Manager for Specialty Detectors and a Senior Application Scientist at Mirion Technologies, focused on developing custom high-purity germanium (HPGe) detector solutions for challenging and unique applications. She joined Mirion in 2012 (formerly Canberra Industries) as a physicist and has worked on a variety of projects offering physics support and doing validation and testing for different products. Gabriela has a Ph.D. in Experimental Nuclear Physics from the University of Cologne, Germany. Before joining Mirion, Gabriela held a Postdoctoral Research position at Yale University where she helped maintain and use a large array of HPGe Clover detectors for nuclear physics measurements and experiments. In the last few years, she has played an active role in promoting new technologies that help customers select the best radiation detection and instrumentation for their applications.

Jim Zickefoose is a Sr. Scientist and R&D Physics Manager at Mirion Technologies in Meriden CT. In these roles he concentrates on driving new technology development across the various Mirion divisions and incorporating those technologies in new or existing products. He joined Mirion in 2010 directly after earning a PhD in physics from the University of Connecticut with a concentration in experimental nuclear astrophysics. During his PhD research Jim studied carbon fusion reactions at accelerator facilities in Caserta, Italy and Bochum, Germany. Prior to his time at UConn Jim earned an Honors Degree in physics from the University of Adelaide.

Note: coffee and cookies at 3:00 outside the lecture room.

Prof. Niloy Dutta, Department of Physics, University of Connecticut

All Optical Correlator

Prof. Geoff Potvin, FIU

UConn physics departmental colloquium

Title and abstract: TBD

Prof. Jason Hancock, Department of Physics, University of Connecticut

Introduction to inelastic X-ray scattering

Prof. Lance Dixon, Stanford University

The DNA of Particle Scattering

Scattering amplitudes are the arena where quantum field theory meets particle experiments, for example at the Large Hadron Collider where the copious scattering of quarks and gluons in quantum chromodynamics (QCD) produces Higgs bosons and many backgrounds to searches for new physics. Particle scattering in QCD and other gauge theories is far simpler than standard perturbative approaches would suggest. Modern approaches based on unitarity and bootstrapping dramatically simplify many computations previously done with Feynman diagrams. Even so, the final results are often highly intricate, multivariate mathematical functions, which are difficult to describe, let alone compute. In many cases, the functions have a “genetic code” underlying them, called the symbol, which reveals much of their structure. The symbol is a linear combination of words, sequences of letters analogous to sequences of DNA base pairs. Understanding the alphabet, and then reading the code, exposes the physics and mathematics underlying the scattering process, including new symmetries. For example, the two scattering amplitudes that are known to the highest orders in perturbation theory (8 loops) are related to each other by a mysterious antipodal duality, which involves reading the code backwards as well as forwards. A third scattering amplitude, which contains both of these as limits, has an antipodal self-duality which “explains” the other duality. However, we still don’t know `who ordered’ antipodal (self-)duality, or what it really means.

Dr. Ming Li

UConn Physics Colloquium

Title and abstract: TBD

Prof. Carlos Trallero, Department of Physics, University of Connecticut

Dynamics at quantum time scales

Prof. Ilya Sochnikov, Department of Physics, University of Connecticut

Quantum Sensors for Quantum Materials Research