PHYSICS COLLOQUIUM SCHEDULE |
SPRING 2022 |
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The Colloquia begin at 3:00pm on Thursdays. Note the change of time!
See individual listings for mode of presentation, zoom or in person. Fall 2021 Colloquium Schedule Department of Physics Colloquium Committee: David Tanner (chair), Paul Avery, Konstantin Matchev, Mark Meisel, Tarek Saab, Christopher Stanton, and BingKan Xue |
January 10 (Monday) - Special Colloquium: 4:05pm |
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| Speaker | Benjamin Geisler (U. Duisberg-Essen) | |
| Delivery | via Zoom | |
| Title | Exploring the Physics of Complex Oxides: From First Principles to Deep Learning | |
| Abstract | Transition metal oxides host a variety of intriguing physical phenomena that result from electronic correlations and the strong coupling of charge, spin, orbital, and lattice degrees of freedom. Precise atomic-scale growth techniques yield complex oxides which exhibit novel effects that are absent in the constituent bulk compounds. High-performance computing proves to be essential for a fundamental understanding of the underlying mechanisms. In the first part of this talk, I will demonstrate in the spirit of a first-principles materials design how to devise artificial transition metal oxides with tailored thermoelectric properties for energy conversion applications [1, 2]. The second part is motivated by the recent observation of superconductivity in infinite-layer NdNiO2 films on SrTiO3(001) [3], which is absent in bulk NdNiO2. Simulations unraveled the key role of the interface: Polarity mismatch drives a surprising electronic reconstruction that results in the emergence of a correlated two-dimensional electron gas in the substrate. The concomitant depletion of the self-doping Nd 5d states renders infinite-layer nickelates close to cuprate superconductors [4]. Finally, I will provide a broader perspective on the infinite-layer materials class and illustrate how artificial intelligence, firmly rooted in fundamental physical principles, allows unconventional insights and, with its fast predictive power, complements modern materials design [5]. [1] B. Geisler, P. Yordanov, M. E. Gruner, B. Keimer, and R. Pentcheva, PSSB 2100270 (2021) [2] B. Geisler and R. Pentcheva, WO 2018/146269, Patent granted (2020) [3] D. Li et al., Nature 572, 624 (2019) [4] B. Geisler and R. Pentcheva, Phys. Rev. B 102, 020502(R) (2020) [5] A. Sahinovic and B. Geisler, Phys. Rev. Research 3, L042022 (2021) | |
| Host | Peter Hirschfeld | |
January 12 (Wednesday) - Special Colloquium: 2:00pm in 2165 |
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| Speaker | Craig Group (University of Virginia) | |
| Delivery | In person and via Zoom | |
| Title | Expanding the search for dark matter with new accelerator-based experiments | |
| Abstract | The evidence for dark matter is strong. However, the constituents of dark matter are still unknown, and the viable possibilities span a very large mass range. Specific scenarios for the origin of dark matter sharpen the focus on a narrower range of masses: the natural scenario where dark matter originates from thermal contact with familiar matter in the early Universe requires the DM mass to lie within about an MeV to 100 TeV. Considerable experimental attention has been given to exploring Weakly Interacting Massive Particles in the upper end of this range (few GeV - ~TeV), while the region ~MeV to ~GeV is largely unexplored. Most of the stable constituents of known matter have masses in this lower range, tantalizing hints for physics beyond the Standard Model have been found here, and a thermal origin for dark matter works in a simple and predictive manner in this mass range as well. It is therefore a priority to explore. If there is an interaction between light DM and ordinary matter, as there must be in the case of a thermal origin, then there necessarily is a production mechanism in accelerator-based experiments. The most sensitive way, (if the interaction is not electron-phobic) to search for this production is to use a primary electron beam to produce DM in fixed-target collisions. The Light Dark Matter eXperiment (LDMX) is a planned electron-beam fixed-target missing-momentum experiment that has unique sensitivity to light DM in the sub-GeV range. I will give an overview of the theoretical motivation, the main experimental challenges and how they are addressed, as well as projected sensitivities in comparison to other experiments. | |
| Host | Andrey Korytov | |
January 13 (Thursday) |
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January 18 (Tuesday) - Special Colloquium: 4:00pm |
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| Speaker | Yaxian Wang (Harvard University) | |
| Delivery | via Zoom | |
| Title | Unconventional transport phenomena in quantum materials | |
| Abstract | An ever-increasing societal demand calls for sustainable energy and quantum information. Elucidating exotic transport and response phenomena in quantum materials is needed not only in designing next-generation modern devices, but also in discovering new physics. In this talk, I will present two of my recent theoretical discoveries in goniopolar materials and hydrodynamic transport. More specifically, I constructed the theory of axis-dependent conduction polarity, termed "goniopolar," where the same population of charge carriers can simultaneously conduct as n-type and p-type along orthogonal crystallographic axes, originating from the Fermi surface topology. I built a consolidated analytical model and proposed the chemical design principles in semimetals and semiconductors. My predictions enabled transverse thermoelectric devices with an unprecedentedly high figure of merit, which can serve as a promising route to improve energy conversion. Further, in quantum materials with nontrivial band topologies and strong interactions, electron scattering can give rise to unusual transport phenomena. For example, electrons can flow collectively, termed "hydrodynamic" exhibiting classical fluid phenomena such as vortices and Poiseuille flow. I utilized first principles tools to investigate the hierarchy of electron-scattering lifetimes in layered semimetal tungsten ditelluride (WTe2) at different temperatures, among which the phonon-mediated scattering mechanism could give rise to hydrodynamic behavior at intermediate temperatures. The theory also shows quantitative agreement with spatial electron current profiles measured using cryogenic scanning magnetometry within an exfoliated WTe2 sample. This microscopic mechanism opens up new possibilities in the search for hydrodynamic flow and strong interactions in high carrier density materials, which I will elaborate on with generalized fingerprints of electronic and phononic structures. Finally, perspectives for the future research directions into emerging energy and quantum materials will also be provided. | |
| Host | Hai Ping Cheng | |
January 20 (Thursday) |
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| Speaker | Elizabeth Lee (University of Chicago) | |
| Delivery | via Zoom | |
| Title | Quantum-classical simulations of electronic motion and structure in hard and soft matter | |
| Abstract | Quantum mechanical behavior of electrons in condensed phase environments, i.e., liquids and solids, is fundamental to both science and technology. Here, I introduce computational frameworks to probe electronic phenomena in soft and hard matter using quantum-classical simulations. First, a phenomenological approach based on a tight-binding model is presented to simulate the dynamics of optically-excited polymer assembly. From these simulations, I discuss how exciton dynamics relate to the conformational fluctuations of polymers at the molecular level. Secondly, I demonstrate a neural network method with electronic structure calculations to explore the free energy landscape of chemical reactions in condensed phase systems. The efficacy of this approach is illustrated based on the molecular dissociation of nitrogen gas on metal surfaces. Finally, I apply the neural network method to address an open challenge in solid-state quantum defects. A mechanistic understanding of spin defect formation is presented for the divacancy complex in silicon carbide, a leading qubit candidate. This study shows that the electronic structure and dynamics of spin defects are keys to designing for quantum information science. | |
| Host | Chris Stanton | |
January 24 (Monday) - Special Colloquium: 4:05pm |
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| Speaker | Qimin Yan (Temple University) | |
| Delivery | via Zoom | |
| Title | Data-centric materials design in the quantum regime: motif learning and symmetry-guided discovery | |
| Abstract | Materials design in the quantum regime call for the integration of multi-tier materials information that go beyond atomic structures. Many quantum behaviors are greatly controlled by local symmetries and local bonding environments. In this talk, motivated by Pauling's rules, I will show that local bonding environments (motifs) can be incorporated in a graph-based machine learning architecture to make reliable property predictions for solid-state quantum materials including complex metal oxides. I will demonstrate that the unsupervised machine (Atom2Vec and Motif2Vec) can learn the basic properties of atoms and motifs by themselves from the extensive database of known materials. Clustering of atoms and motifs in vector space classifies them into meaningful groups consistent with human knowledge. The proposed atom-motif dual network model demonstrates the feasibility to incorporate beyond-atom materials information in a graph network framework and achieves the state-of-the-art performance in predicting the complex properties of solid-state quantum materials. With these tools developed, I will discuss the potential application of artificial intelligence in the field of quantum materials design, including two-dimensional quantum materials and defect qubit-based quantum information science. I will also discuss the continued development of AI-driven technologies for quantum phenomena, with the consideration of symmetries, orbital interactions, and physical constraints. | |
| Host | Greg Stewart | |
January 27 (Thursday) |
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| Speaker | Philip Chang (UCSD) | |
| Delivery | via Zoom | |
| Title | New frontiers of electroweak physics at the LHC | |
| Abstract | The unification of electroweak interaction took us step closer to Einstein's dream of a unified theory of nature. However, the details of the electroweak unification have remained elusive. Now, with the discovery of the Higgs boson, the studies of electroweak interaction at the LHC is in full swing. This talk will discuss the recent developments in expansions of the final states being studied for electroweak interaction at the LHC in order to advance our knowledge of the electroweak symmetry breaking. Finally, I will briefly discuss the challenges that lie ahead for the electroweak physics at the LHC, and the steps being taken to address them. | |
| Host | Andrey Korytov | |
January 28 (Friday) - 2022 IFT Colloquium at 3:00 pm |
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| Speaker | John Klauder (University of Florida) | |
| Recording | Talk | |
| Title | Most Classical Systems Require Affine Quantization: Including gravity and most field theory | |
| Abstract | Affine quantization (AQ), a parallel procedure to canonical quantization, is focused on quantization when the coordinate space is reduced. The half-harmonic oscillator, which is limited to the positive real axis, is a clear example of what AQ can do. Several simple examples are followed with an AQ of two forms of field theories, as well as gravity, which lead to procedures that eliminate any nonrenormalizablilty.
References
With this talk we celebrate John's 90th birthday! |
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| Host | Sergei Shabanov and David Tanner | |
February 1 (Tuesday) - Special Colloquium at 3:00pm |
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| Speaker | Alexx Perloff (University of Colorado) | |
| Delivery | via Zoom | |
| Title | Exploring Novel Signatures for Dark Matter at the LHC | |
| Abstract | The nature of dark matter (DM) remains one of the outstanding mysteries in particle physics and presents strong evidence for physics beyond the standard model (SM). Despite years of searching, experiments at the Large Hadron Collider (LHC) at CERN have yet to see any evidence for an excess of events with large missing transverse momentum, a possible indication of certain DM signatures. Considering this, I will discuss an alternative strategy to look for collider produced DM, which is based on a suite of models containing a dark sector of particles and a new strong force called "dark QCD." This new strongly coupled dark sector would provide both a stable, composite dark matter candidate in the form of "dark hadrons" as well as a tantalizing suite of phenomenology. I will present ongoing and future searches at the Compact Muon Solenoid (CMS) experiment looking at phenomenological signatures of dark QCD, focusing on emerging jets. I will also discuss how new machine learning techniques and upgrades to the CMS trigger system will enhance future searches for dark sector models. | |
| Host | Andrey Korytov | |
February 3 (Thursday) |
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| Speaker | Chunjing Jia (Stanford University) | |
| Delivery | via Zoom | |
| Title | Quantum Materials Design: AI-assisted in silico simulations | |
| Abstract | We are in a golden age of quantum materials with surprising advances in materials performance. Developing
predictive theories and new theoretical methods for the investigation of novel phenomena and materials with
superior functionalities represent major challenges for theoretical condensed matter physics. The
complexities of theoretical modeling for quantum materials mainly lie in two aspects: (1) how to build
theory to effectively address the intertwining degrees of freedom and incorporate the strong correlation
effect; and (2) how to strategically search in the gigantic phase space of both chemical compositions and
materials structures, in order to tailor desired properties for next-generation materials design.
AI-assisted algorithms have shown great promise in both aspects. Specifically, complex physics phase space
could be mapped into highly nonlinear AI models, so that hidden patterns could be effectively captured to
make informative understandings and predictions.
I will use infinite-layer nickelate as an example system to talk about my theoretical investigation of quantum materials. As a long sought-after superconducting system, the experimental realization of infinite-layer nickelates was one of the most exciting news in the condensed matter physics community in recent years.[1] To understand the fundamental physics of this system, a theoretical approach combining ab initio materials-specific methods with numerically exact quantum many-body methods, such as exact diagonalization and density matrix renormalization group, was implemented. These theories have provided fundamental understanding of electronic structure[2][3], superconductivity and competing orders[4] of infinite-layer nickelates, and have shown great consistency with experiments. In the remaining part of my talk, I will discuss how AI could further assist this theoretical endeavor. I will discuss some of my ongoing and future studies using state-of-the-art AI techniques, such as neural network quantum state[5] and crystal graph convolutional neural network[6], to solve cutting-edge problems including many-body dynamics, structural prediction, and material properties prediction. References: [1] Li et al, Nature 572, 624 (2019) [2] Hepting et al, Nature Materials 19 (4), 381-385 (2020) [3] Been et al, Physical Review X 11, 011050 (2021) [4] Peng et al, arXiv:2110.07593 (2021) [5] Carleo et al, Science 355, 602 (2017) [6] Xie et al, Physical Review Letters 120, 145301 (2018) |
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| Host | Xiaoguang Zhang | |
February 8 (Tuesday) - Special Colloquium at 3:00pm |
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| Speaker | Dylan Rankin (MIT) | |
| Delivery | via Zoom | |
| Title | Accelerating Discovery through Deep Learning | |
| Abstract | In recent years deep learning has become an increasingly common tool in high energy physics. Despite its prevalence, however, the most effective ways to use deep learning techniques are still unclear. In this talk I will discuss how advances in both hardware and software have allowed for faster and more efficient inference, and how these advances are enabling more sensitive detectors and powerful data analysis. I will also present new deep learning methods that are broadening the possibilities for searches and measurements at the Large Hadron Collider and beyond. | |
| Host | Andrey Korytov | |
February 10 (Thursday) |
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| Speaker | David Sperka (Boston University) | |
| Delivery | via Zoom | |
| Title | The Evolution of the CMS Trigger System for LHC Run 3 and Beyond | |
| Abstract | A number of reported experimental anomalies in particle physics have grown in strength over the last year and will drive the next generation of LHC searches. The measured value of the muon's anomalous magnetic moment at Fermilab and tests the lepton flavor universality by LHCb and other experiments have exceeded the 3 standard deviation threshold for evidence of new physics. Furthermore, searches for traditional dark matter candidates have not observed any positive signal. For CMS to test the full class of new physics models that can explain these results, or to perhaps directly confirm them, will require a major evolution of the experiment's trigger strategy. In this talk I will describe my view on the current state of the particle physics field, and how the flexibility of the CMS trigger system can be leveraged to keep the experiment at the doorstep of a major discovery. In particular I will describe the "data scouting" and "data parking" paradigms that were successfully deployed in Run 2 and how they will evolve for Run 3 to address the major open questions in particle physics. | |
| Host | Andrey Korytov | |
February 15 (Tuesday) - Special Colloquium at 4:05pm |
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| Speaker | Tamara Schroder (CERN) | |
| Delivery | via Zoom | |
| Title | Into the great wide open: in search for new physics with multiple leptons at the LHC | |
| Abstract | The primary goal of the Large Hadron Collider (LHC) has been to discover the mechanism of electroweak symmetry breaking (EWSB). The discovery of the Standard Model (SM)-like Higgs boson in 2012 was the first step to achieve this. However, the underlying nature of EWSB remains unknown. Additionally, the SM cannot explain the origin of neutrino masses, the asymmetry between matter and antimatter in our universe, or the nature of dark matter and dark energy. It also cannot address important conceptual questions, such as why is the Higgs boson so light compared to the Planck scale, or what are the underlying dynamics through which the Higgs field provides masses to the fundamental particles. Even though the LHC has not discovered any Beyond the Standard Model physics, there are multiple hints in various areas of particle physics which could revolutionize our understanding of the elementary particles and the forces between them, leading to the start of a new Higgs and Flavour Era. In this talk I will dive into promising new physics models that could address some of the shortcomings of the SM and could potentially explain some of the observed tensions in the particle physics landscape. Being potentially at the reach of the LHC collision energy, the search for these new physics signals in the multilepton final state could be the key to access a new phase in particle physics exploration. | |
| Host | Andrey Korytov | |
February 17 (Thursday) |
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| Speaker | Zeynep Demiragli (Boston University) | |
| Delivery | via Zoom | |
| Title | A shot in the dark | |
| Abstract | The experiments at the Large Hadron Collider at CERN are at the energy frontier of particle physics, searching for answers to fundamental questions of nature. In particular, dark matter presents strong evidence for physics beyond the standard model. However, there is no experimental evidence of its non-gravitational interaction with standard model particles. If dark matter has non-gravitational interactions with the standard model particles, we could be producing the dark matter particles in the proton-proton collisions at the LHC. While the dark matter particles would not produce an observable signal in the detector, they may recoil with large transverse momentum against visible particles resulting in an overall transverse momentum imbalance in the collision event. In this talk, I will review the searches for dark matter particles in the missing momentum final states in association with jets at the Compact Muon Solenoid (CMS) experiment. | |
| Host | Andrey Korytov | |
February 24 (Thursday) |
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March 3 (Thursday) |
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March 10 - Spring Break - No Colloquium |
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March 17 - March Meeting - No Colloquium |
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March 24 (Thursday) |
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| Speaker | Wei Xue (UF) | |
| Delivery | Recording | |
| Title | New ideas of dark matter theories and searches | |
| Abstract | The nature of dark matter is a central question in fundamental physics. To discover dark matter, we need to build new dark matter frameworks and new search strategies. I will present my recent works on dark matter experiment, theory and dark matter evolution in the early universe. First, I will introduce a new development in an effective theory of helium superfluid. The theory development is the first step of a long project to build a dark matter direct detection detector using helium superfluid to search for MeV-GeV mass dark matter. Second, I will introduce a new paradigm, where dark matter is made up of a novel form of matter, called "gapped continuum," rather than an ordinary particle. Third, I will discuss the momentum spectrum of axion dark matter during the a phase transition in the early universe. | |
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March 31 (Thursday) |
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| Speaker | Nick Bonesteel | |
| Delivery | Recording | |
| Title | Quantum Computing with the Exchange Interaction | |
| Abstract | In exchange-only quantum computation, qubits are encoded using three or more spin-1/2 particles (e.g., electrons in quantum dots) and quantum gates can be performed by switching on and off, or "pulsing," the isotropic exchange interaction between spins. Finding efficient pulse sequences for realizing two-qubit quantum gates in this way is complicated by the large search space of sequences and has typically involved numerical brute force search. In this talk I will review the current state-of-the-art in exchange-only quantum computation and give a simple analytic derivation of the most efficient known exchange-pulse sequence for carrying out a controlled-NOT gate [1], originally found numerically by Fong and Wandzura [2]. I will then show how the ideas behind this derivation can be used to analytically find new pulse sequences for two-qubit gates beyond controlled-NOT [3]. [1] D. Zeuch and N.E. Bonesteel, PRA 93, 010303 (2016). [2] B.H. Fong and S.M. Wandzura, Quantum Inf. Comput. 11, 1003 (2011). [3] D. Zeuch and N.E. Bonesteel, PRB 102, 075311 (2020). | |
| Host | Chris Stanton | |
April 7 (Thursday) |
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| Speaker | Curtis R. Taylor (UF Dept. of Mech. & Aerospace Eng and Associate Dean for Undergraduate Student Affairs, UF College of Engineering) | |
| Delivery | Recording | |
| Title | Physics Education - A Platform for Success | |
| Abstract | In this presentation, I will share my career path in physics and engineering. I will highlight my research interests in surface science and nanoscale mechanics here at UF as well as experiences working in the U.S. government as an intelligence analyst, the Lawrence Berkeley National Lab, U.S. Air Force Research Lab, and several companies. Lastly, I will highlight opportunities in physics education and the issue of “the missing physicist“ - an issue of national importance that was recently published under the same name in the journal of Science. | |
| Host | Mark Meisel (faculty) and Bridgette Gifford (student, President of the Gator Chapter of the National Society of Black Physicists (NSBP)) | |
April 14 (Thursday) |
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| Speaker | Jonathan Feng (UC Irvine) | |
| Delivery | via Zoom | |
| Title | Forward-Looking Physics at the LHC | |
| Abstract | Particle physics is at a critical juncture. All the particles of the Standard Model have been discovered, but no new ones have appeared, and there are still many outstanding questions. In recent years, it has become clear that the physics potential of the Large Hadron Collider at CERN has not been fully exploited. In particular, forward collisions, which produce particles along the beamline with enormous rates, are a treasure trove of physics, containing the highest-energy neutrinos ever produced by humans, possible evidence for dark matter, milli-charged particles, and new forces, and a wealth of other valuable information. This talk will describe FASER, an experiment that has just been constructed and will begin taking data in the forward region in a few months, as well as the Forward Physics Facility, a proposal to fully realize the potential of forward physics in the High Luminosity LHC era. | |
| Host | Konstantin Matchev | |