The collision of extremely dense objects such as neutron stars and black holes provides us with a remarkable laboratory to study the laws of physics in extreme environment. Through the study of merging neutron stars, we learn about gravity, the properties of dense matter, the formation of heavy nuclei (gold, platinum, uranium) and neutrino physics. In this talk, I will review the physical processes at play in neutron star mergers and discuss what numerical simulations of colliding neutron stars tell us about the ways in which these systems can be used to better understand cold nuclear matter and astrophysical nucleosynthesis.

Topological quantum computing involves using non-Abelian Majorana zero modes for carrying out error-free fault-tolerant quantum computing. This is the preferred quantum computing platform of Microsoft. I will discuss the current status of the search for non-Abelian Majorana zero modes in solid state systems, discussing both theory and experiment. I will also provide my personal prognosis on what the future holds for the subject.

All cells sense and respond to physical and chemical cues in their environments. They accomplish this through signal transduction systems—networks of interacting proteins that detect and interpret specific input signals and control appropriate cellular responses. In bacteria, these systems are found in remarkable numbers within individual organisms and across different bacterial species. They play a central role in regulating basic aspects of microbial physiology and mediate responses to diverse environmental signals. I will describe work in which we have explored the organization and properties of these networks in the particularly well studied and genetically tractable organism Escherichia coli.

The proton and neutron, known as nucleons, are the fundamental building blocks of all atomic nuclei that make up essentially all the visible matter in the universe, including the stars, the planets, and us. More than 50 years of study has revealed that nucleons are composed of elementary particles called quarks and gluons, whose interactions and dynamics are governed by Quantum Chromodynamics (QCD). However, many profound questions remain. In this talk, I will demonstrate that the newly upgraded CEBAF facility at Jefferson Lab and the future Electron-Ion Collider are two complementary and necessary facilities that are capable of exploring the inner structure of nucleons and nuclei at sub-femtometer distance scale, enabling a new emerging science and technology – Nuclear Femtography. These facilities will help address the most compelling unanswered questions about the elementary building blocks of our visible world, taking us to the next frontier of the Standard Model of physics.

PRX is published by the American Physical Society, a nonprofit membership society of scientists. Its mission goal is to select around 250 *landmark* papers a year from all fields of physics and showcase them to a broad and multidisciplinary readership.

Is your paper a good match for PRX? Or asked differently, what papers qualify as *landmark* papers?

How do the PRX editors actually select such papers? Are such selections always accurate?

How can you, as an author, navigate PRX’s editorial and peer-review process effectively and get the most out of your interactions with the editors and referees?

I will use the talk to discuss with you how to answer these questions. Many of these questions do not have a black-and-white answer in the case of a single paper. Open-minded, reasoned, and constructive dialogues amongst the authors, the editors, and the referees are key to making each concrete process a meaningful and productive experience, and sometimes even a pleasure, for everyone.

Quantum networks have the potential to support capabilities that are unachievable with classical means alone. Besides quantum cryptographic applications, quantum networks have a variety of scientific uses and can help scale up quantum computers. However, the realization of quantum networks faces formidable challenges which include noise that is inflicted upon quantum states, and loss that is suffered by photons which act as information carriers between distributed quantum information processors. In this talk, I will introduce some of the fundamentals of quantum communication, provide examples of noise and loss in quantum systems with real-world examples, and discuss some of the ways that can help us cope with these challenges. At the end of the talk, I will identify several topics that are of research interest to the quantum networks community.

Under specific conditions, exotic Cooper pairing state can emerge with a non-uniform equilibrium order parameter, possessing a finite center-of-mass momentum. Such spatially dependent order parameters (Δ𝑃(r)) can generically feature variations in either their amplitude or phase — or a combination of both. Utilizing Spectroscopic Imaging Scanning Tunneling Microscopy (SI-STM), we’ve identified two primary PDW states in the iron pnictide superconductor, EuRbFe4As4 (ER-1144), a material that features co-existing superconductivity (Tc ≈ 37 kelvin) and magnetism (Tm ≈ 15 kelvin). In the ferromagnetic superconducting phase, the first type is characterized by a superconducting gap that has a long-range, unidirectional spatial modulation (𝛥𝑃~|𝛥0|cos(Q∙r)) in the absence of any other translational symmetry breaking density-wave orders. The second type features an anisotropic Doppler energy shift in reciprocal space due to the phase winding (𝛥𝑃~|𝛥0|𝑒𝑖Q∙r). In contrast, all the striking features are completely suppressed crossing the magnetic transition. Additionally, both PDW states are also impacted by an out-of-plane external magnetic field, evidenced by the Bogoliubov quasiparticle spectrum imaging. Our findings provide valuable insights into the intricate nature of the PDW states and the interplay between magnetism and superconducting order.

Massive stars, by which we mean those stars evolving through all the stable nuclear burning stages, play a fundamental role in the evolution of the Universe. Therefore, a good knowledge of how they evolve is required in order to shed light on many topical subjects like, e.g., the chemical evolution of the galaxies and the nature of the sources of gravitational waves. In the last years three main questions – still debated – rose in the community working on massive stars. They concern (1) the compactness of massive stars at the presupernova stage as an indicator of their explodability, (2) the nature of the remnant after the explosion, and in particular the maximum mass of a stellar black hole, and (3) the so called “Red Supergiant (RSG) problem”, i.e. the lack of observed supernovae associated with the observed most luminous RSGs. In this colloquium I will address these questions by firstly reviewing our current understanding of the presupernova evolution of massive stars.

Fundamental questions in nuclear physics such as, “What is the nature of hot and dense matter?” and “What is the origin of r-process nuclei?” are deeply connected to neutron star observations. In this talk, I will explain how we are answering these questions using a combination of data from nuclear experiments, data from neutron star observations, theoretical models of hot and dense matter, and numerical simulations. Answering these questions demands a level of effort beyond that of a single research group, so I explain how progress is being made through collaborations like the Nuclear Physics for Multi-Messenger Mergers Focused Research Hub. I summarize recent results on both the speed of sound and the composition of dense matter. I show how we are enhancing astrophysical simulations by improving the nuclear physics input. Finally, I show how we are using machine learning to accelerate progress.

The visible world around us is made up of atoms, with protons and neutrons forming the nuclei at their core. Together, protons and neutrons make up most of the mass of everything we see in the universe today, from massive galaxies to individual people. Protons and neutrons themselves are complicated many-body quantum states whose properties are determined by the quarks and gluons that they are comprised of. The quest to understand in detail the structure of protons, neutrons, and nuclei is nothing less that an attempt to answer the questions “What are we made of? What is matter?” The Electron Ion Collider (EIC), to be built by JLab and BNL, will be a unique new machine to collide polarized electrons off polarized protons and light nuclei, providing the capability to study multi-dimensional tomographic images of hadronic matter, and collective effects of gluons in nuclei. In this colloquium I will motivate the physics program at the EIC and the unique new machine and detectors that will be required to answer these fundamental questions.

In the study of quantum matter, measurements have traditionally been viewed as a means of learning about a system. Measurements can, nevertheless, play a more active role—generating novel quantum phenomena that may be difficult or impossible to realize in measurement-free settings. As an interesting example, I will discuss how measurements can dramatically alter universal properties of quantum systems tuned to a phase transition. I will also highlight a path to experimental realization in analog quantum simulators based on Rydberg atom arrays. Finally, I will describe how these ideas inform optimization of quantum teleportation protocols against imperfections—establishing a long-term quantum science application of ‘measurement-altered quantum criticality’.

Symmetry is central to our understanding of natural phenomena. And a Sagnac interferometer, first invented by George Sagnac for the detection of the hypothetical “ether” in the Michelson–Gale experiment [1] a century ago, is intrinsically sensitive to broken time-reversal symmetry (TRS). In this talk, I will first describe a loop-less version of the Sagnac interferometer and microscope that has achieved unprecedented nanoradian level Kerr and Faraday sensitivity even at DC. With this Sagnac technique, I will discuss a few examples of our Sagnac studies of 2D magnetism and superconductivity. In exfoliated Cr2Ge2Te6 (CGT), we report [2] the discovery of intrinsic ferromagnetism in 2D van der Walls crystals, defying the well-known Mermin-Wagner theorem. In epitaxial Bi/Ni bilayer samples, we report [3] the observation of 2D superconductivity that spontaneously breaks TRS, which might have an order parameter with a nonzero phase winding number around the Fermi surface, making it a rare example of a 2D topological superconductor. In the Fe-Chalcogenide superconductor FeTe1−xSex, we found intertwined magnetism and superconductivity in its topological surface state [4]. Additionally, our study on exfoliated FeTe1−xSex flakes indicates the existence of a chiral edge state that may be useful for robust quantum computing (unpublished).

1. “The Effect of the Earth’s Rotation on the Velocity of Light, II” Michelson, A. A.; Gale, Henry G. (1925). Astrophysical Journal. 61: 140.
2. “Discovery of intrinsic ferromagnetism in 2D van der Waals crystals”, Nature, 546, 265-269 (2017).
3. “Time-Reversal-Symmetry-Breaking Superconductivity in Epitaxial Bismuth/Nickel Bilayers”, Science Advances, 3, 3, e1602579 (2017).
4. “Revealing the Origin of Time-Reversal Symmetry Breaking in Fe-Chalcogenide Superconductor FeTe1−xSex”. Physical Review Letters, 130(4):046702 (2023)

The complex interplay between the quantum degrees of freedom in oxides is known to cause a rich variety of intriguing emergent phenomena. While model Hamiltonians are often used to capture the underlying physics, they could be difficult to solve theoretically. This challenge calls for model-based designs for materials synthesis and measurement controls to experimentally simulate the corresponding behaviors. In this talk, I will review examples from our recent work that exploited this strategy to investigate the correlation-topology interplay in the Hubbard Hamiltonian, metallization of the dipolar spin ice Hamiltonian, and competition between orthogonal magnetic anisotropy. The results showcase the use of symmetry as the guide to implement the key ingredients of the targeted model in the experiment designs, which synergistically combine atomic layering synthesis, single-crystal growth, ultralow-temperature high-field transport measurements, and/or synchrotron x-ray scattering with multi-modal controls. New opportunities enabled by most recent capability advances will be discussed as well.

Over the last century, the construction and discovery of the Standard Model of particle physics has been one of the greatest accomplishments in physics. To explore this new frontier, we built larger and larger colliders utilizing the two charged particles that are easiest to produce and manipulate, the proton and the electron. As we contemplate the future of high energy colliders, the use of these particles fundamentally limits our potential energy reach: the low electron mass due to synchrotron radiation and the proton due to its composite nature. Luckily, the Standard Model provides an alternative: the muon. In this talk, I’ll discuss the challenges and possibilities of a muon collider, and give an overview of recent progress towards making one a reality.

The annual Honors Day celebration will be in Room 272C/Ballroom C at the Student Union.
We look forward to celebrating our staff for their extraordinary service and our students for their academic, leadership, and research achievements. The Society of Physics Students and Graduate Physics Society will also honor outstanding faculty members for exemplary teaching and advising.

The event begins at 3:30 pm.

Questions that drive searches for physics beyond the Standard Model include the physical origin of the cosmic baryon asymmetry and of dark matter. Quark dynamics, as realized through the theory of quantum chromodynamics (QCD), can appear in these studies in very different ways. In this talk, I develop these possibilities explicitly, first describing the role of QCD in ultra-sensitive searches for new physics, particularly at low energies, and then turning to how its features could be exploited in describing the undiscovered universe, along with the essential observational and experimental tests that could confirm them.

The strongest fundamental force of nature generates ~96% of the mass of the visible universe and binds together the building blocks of quantum chromodynamics, quarks and gluons, within the proton. At temperatures of a few trillion Kelvin or densities tens of trillions times more dense than iron, these quarks are no longer bound within protons and can form entirely new states of matter. It is possible to unlock these quark phases in heavy-ion collisions that reach the hottest temperatures on Earth or potentially in the core of neutron stars that have densities many times larger than that of a nucleus. In this talk, we will explore different ways to study the phases of matter of quarks from the lab using heavy-ion collision and in the cosmos using X-Ray measurements of neutron stars or gravitational waves from binary neutron star mergers.

Co-presented with Adrian Del Maestro (Physics/EECS), Kate Page (MSE), Claudia Rawn (MSE), and Corey Hodge (UT MRSEC)

The University of Tennessee has recently been awarded a prestigious Materials Research Science and Engineering Center by the National Science Foundation. The Center for Advanced Materials and Manufacturing is hosted at IAMM HQ, Knoxville as well as the Shull Wollan Center on the ORNL Campus. This Center builds on longstanding partnerships with ORNL in advanced computing, neutron science, and materials. The MRSEC involves more than 80 faculty, postdocs, and students and joins the network of MRSECs nationwide in offering unique capabilities to the national science community. This talk will present the center, its research, education, and outreach activities as well as its connections with the facilities and ways to get involved.

The formulation of quantum mechanics in the late 1920s forever changed physics. More recently, quantum materials have emerged, offering fascinating opportunities in condensed matter physics. Elementary interactions among elements such as electrons, phonons, and other quasiparticles in quantum materials give rise to the emergence of intriguing phases and offer enormous opportunities for the development of quantum technologies. But investigating these interactions at the relevant length scale requires high-resolution methods. Traditional far-field optical imaging and spectroscopy techniques are constrained by the diffraction limit of light. Interestingly, during the same period in the late 1920s, a visionary scientist named Synge introduced a groundbreaking concept that could circumvent the diffraction limit. Synge shared his idea with Einstein, who encouraged him to publish it. After many years of various pioneering works by different groups, a powerful modern nano-optical technique, a variant of Synge’s original idea, was born. In this talk, I will introduce this technique and give examples of high-resolution probing of nanoscale physical phenomena and interactions in two classes of quantum materials: correlated oxides and van der Waals (vdW) crystals. Our recent results reveal how an applied field perturbs dopant distribution at the nanoscale in correlated oxides such as rare-earth nickelates (RNiO3 where R = rare-earth element), leading to ordered reconfigurable phases. This reconfigurability enables the design of robust artificial synapses and opens new frontiers for fundamental understanding of memory, learning, and information retention for brain-inspired information processing. Correlated oxides also provide exciting opportunities to reconfigure polaritons, hybrid light-matter modes, in vdW crystals at the nanoscale, due to their highly tunable local optical and electronic properties. I will introduce a hybrid polaritonic-oxide heterostructure platform consisting of vdW crystals, such as hexagonal boron nitride or alpha-phase molybdenum trioxide, transferred on nanoscale oxygen vacancy patterns on the surface of correlated perovskite oxides. Hydrogenation and temperature modulation allow spatially localized conductivity modulation of the oxide nanoscale patterns, enabling robust real-time modulation and nanoscale reconfiguration of hyperbolic polaritons

Excitons are quasiparticles that emerge when a valence electron is promoted in energy to the conduction states, leaving behind a hole that interacts with the electron. Many aspects of exciton physics in traditional insulators are well understood. However, in correlated quantum materials, the situation becomes richer and more complex due to the emergence of many-body excitons, which involve strong electron-electron and electron-spin interactions. In this talk I will explain the technique of resonant inelastic x-ray scattering [1], which we have recently been applying to several aspects of exciton physics. This includes the identification of an antiferromagnetic excitonic insulator state in Sr3Ir2O7 [2], determining the nature of propagating magnetically propagating Hund’s excitons in NiPS3 [3], and the Floquet renormalization of the charge-transfer exciton in La2-xSrxCuO4.

[1] Exploring Quantum Materials with Resonant Inelastic X-Ray Scattering, M. Mitrano, S. Johnston, Young-June Kim, and M. P. M. Dean, submitted (2024)

[2] Antiferromagnetic excitonic insulator state in Sr3Ir2O7, D. G. Mazzone et al., Nature Communications 13, 913 (2022)

[3] Magnetically propagating Hund’s exciton in van der Waals antiferromagnet NiPS3, W. He et al., in press at Nature Communications (2024)

Understanding the origin of life on Earth motivates many of the questions that drive inquiry across all scientific subfields. Certainly, such questions influence nuclear and particle physics research. For example, the matter-antimatter asymmetry observed in today’s Universe is necessary for our existence, but its origin in not well understood. The neutrino may play a significant role in understanding this asymmetry. Specifically, a promising class of theories that explains the asymmetry requires that the neutrino be its own anti-particle. The nuclear process of neutrinoless double-beta decay (0νΒΒ) can only occur if neutrinos have mass and are their own antiparticle. Although it is known that neutrinos have a small mass, we do not know the value or their particle-antiparticle nature. If a rate for 0νΒΒ is measured it will help elucidate the mass, but critically, 0νΒΒ is the only feasible experimental technique to determine if light neutrinos are their own antiparticle. This situation has resulted in a great deal of excitement for 0νΒΒ research.

This Colloquium will discuss the motivations for the search for 0νΒΒ, the experimental issues, and the use of the radiation-detection technology of germanium detectors to search for this process; the Majorana and LEGEND experiments.

A quantum spin liquid (QSL) arises from a highly entangled superposition of many degenerate classical ground states in a frustrated magnet, and is characterized by emergent gauge fields and deconfined fractionalized excitations (spinons). Because such a novel phase of matter is relevant to high-transition-temperature superconductivity and quantum computation, the microscopic understanding of QSL states is a long-sought goal in condensed matter physics. Although Kitaev QSL exists in an exactly solvable spin-1/2 (S=1/2) model on a two-dimensional (2D) honeycomb lattice, there is currently no conclusive identification of a Kitaev QSL material. The 3D pyrochlore lattice of corner-sharing tetrahedra, on the other hand, can host a QSL with U(1) gauge fields called quantum spin ice (QSI), which is a quantum (with effective S=1/2) analog of the classical (with large effective moment) spin ice. The key difference between a QSI and classical spin ice is the predicted presence of the linearly dispersing collective excitations near zero energy, dubbed the “photons” arising from emergent quantum electrodynamics, in addition to the spinons at higher energies. Recently, 3D pyrochlore systems Ce2M2O7 (M = Sn, Zr, Hf) have been suggested as effective S=1/2 QSI candidates, but there has been no evidence of quasielastic magnetic scattering signals from photons, a key signature for a QSI. Here, we use polarized neutron scattering experiments on single crystals of Ce2Zr2O7 to conclusively demonstrate the presence of magnetic excitations near zero energy at 50 mK in addition to the signatures of spinons at higher energies. By comparing the energy (E), wave vector (Q), and polarization dependence of the magnetic excitations with theoretical calculations, we conclude that Ce2Zr2O7 is the first example of a dipolar-octupolar π-flux QSI with dominant dipolar Ising interactions, therefore identifying a microscopic Hamiltonian responsible for a QSL.

This colloquium introduces the underlying theory and computational algorithms used to simulate the low-energy interactions of protons and neutrons using a three-dimensional lattice grid. Some of the topics to be discussed are nuclear clustering, intrinsic shapes, nuclear binding energies and charge radii, the nuclear equation of state, the liquid-vapor transition in nuclear matter, and superfluidity.

A free neutron provides the simplest example of nuclear $\beta$-decay, leading to a unique suite of tests for fundamental parameters of electroweak theory and the Standard Model of particle physics. A free neutron decays into a proton, electron, and antineutrino. This decay can be used to extract the CKM quark-mixing matrix element $V_{ud}$ without the need for nuclear structure corrections, which could resolve present tensions or hunt for new physics. This extraction requires two measurements: the neutron lifetime, $\tau_n$; and the relative coupling strength of the Vector and Axial-Vector currents in the weak interaction, $\lambda$. This talk will provide an overview of this decay process, beginning with measurements of the neutron lifetime. Then, this talk will focus on measuring $\lambda$, presenting an early look at results from the Nab experiment presently commissioning at Oak Ridge National Laboratory.

Over recent decades, the study of strongly correlated quantum materials, in which strong interactions between particles push the system into the non-perturbative regime, has revealed a plethora of new quantum states, each with unique physical properties beyond the reach of perturbation theory. A key hurdle in this arena is the non-perturbative nature of these states, making theoretical description and prediction of them a significant challenge. This talk aims to shed light on how flat band systems provide a distinctive platform for various nontrivial correlated phenomena to emerge as exact solutions in theoretical analysis. This facilitates reliable prediction and robust guidance to identify novel quantum states of matter. Examples such as non-Fermi liquids and the fractional quantum anomalous Hall effect will be illuminated, along with a discussion on yet-to-be-observed quantum states that might emerge in flat band systems, such as fractional quantum anomalous Hall smectic states.

There are many open questions in nuclear physics which only lattice QCD may be able to answer. One example is understanding the nature and origin of the fine-tuning of interactions between nucleons and nuclei observed in nature. The first step toward building a bridge between the underlying theory, QCD, and nuclear observables is full control over one- and two-nucleon systems. While enormous strides have been made in recent years in precision calculations of single-nucleon observables, the history of two-nucleon calculations has generated more questions than answers. In particular, there is a controversy in the literature between calculations performed using different theoretical techniques, even for calculations far from the physical point, chosen due to the exponentially simpler computational properties. In this talk, I will present the history and challenges behind one- and two-nucleon calculations in lattice QCD, as well as advances in understanding and controlling the associated systematics.

Neuromorphic computing is a popular technology for the future of computing. Much of the focus in neuromorphic computing research and development has focused on new architectures, devices, and materials, rather than in the software, algorithms, and applications of these systems. In this talk, I will overview the field of neuromorphic from the computer science perspective. I will give an introduction to spiking neural networks, as well as some of the most common algorithms used in the field. Finally, I will discuss the potential for using neuromorphic systems in real-world applications from scientific data analysis to autonomous vehicles.

Protein crystallography is an established technique for determining the structure and function of many protein systems. These measurements are essential for drug design, enzymology, and more. Light sources dominate this field due to their extremely high brightness, but neutrons have unique advantages such as sensitivity to light nuclei and isotopes. At ORNL, Dynamic Nuclear Polarization (DNP) is being used to take advantage of the nuclear spin dependence of neutron scattering and leverage that to overcome the large brightness disadvantage of neutron sources. The DNP technique will be described, as will test results, and the design and operation of a DNP enhanced IMAGINE instrument which will soon be installed at the High Flux Isotope Reactor (HFIR).

For more than 15 years, NANOGrav and other pulsar-timing array collaborations have been carefully monitoring networks of pulsars across the Milky Way. The goal was to find a tell-tale correlation signature amid the data from all those pulsars that would signal the presence of an all-sky background of nanohertz-frequency gravitational waves, washing through the Galaxy. At the end of June this year, NANOGrav finally announced its evidence for this gravitational-wave background, along with a series of studies that interpreted this signal as either originating from a population of supermassive black-hole binary systems, or as relics from cosmological processes in the very early Universe. I will describe NANOGrav’s journey up to this point, what led to the ultimate breakthrough, how this affects our knowledge of supermassive black holes and the early Universe, and what lies next for gravitational-wave astronomy at nanohertz frequencies.

The strong force in nature, which is at the core of nuclear-physics phenomena, is described by the theory of quantum chromodynamics (QCD). It has long generated an active and growing field of research and discovery. In fact, despite the development of QCD more than half a century ago, plenty of questions remain open into the 21st century: What does the phase diagram of matter governed by strong interactions, such as the interior of neutron stars, look like? How does matter evolve and thermalize after energetic processes such as after the Big Bang or in particle colliders? How do elementary particles in QCD and their interactions give rise to the complex structure of a proton or a nucleus, and their response to various probes? A successful program called lattice QCD has enabled a first-principles look into some properties of matter with the aid of classical computing. At the same time, we have yet to come up with a more powerful computational tool to predict the complex dynamics of matter from the underlying interactions. Can a large reliable (digital or analog) quantum simulator eventually enable studies of the strong force? What does a quantum simulator have to offer to simulate QCD, and how far away are we from such a dream? In this talk, I will describe a vision for how we may go on a journey toward quantum simulating QCD, by taking insights from early to late developments of lattice QCD and its achievements, by motivating the need for novel theoretical, algorithmic, and hardware approaches to quantum-simulating this unique problem, and by providing examples of the early steps taken to date in establishing a quantum-computational lattice-QCD program.

A recurring theme in condensed-matter physics has been the discovery and exploration of macroscopic quantum phenomena as consequences of strong electron-electron interactions, such as magnetism, superconductivity, and fractionalization. Bilayer graphene with a magic-angle artificial twist exemplifies a new paradigm of strongly interacting electrons, as witnessed in the past five years. In fact, naturally occurring rhombohedral graphene multi-layers are also fertile ground for strongly interacting electron physics. In this talk, I will first discuss their theory-oriented spontaneous chiral symmetry breaking, topological orbital magnetization, and quantum anomalous Hall effect at charge neutrality, which have all been observed in experiment. Then I will introduce their experiment-oriented ferromagnetism, superconductivity, electron crystallization, and fractional quantum anomalous Hall effect under ultra-low doping. If time permits, I will show how SU(3) flavor physics analogous to the quark model can also emerge in this system.

Atomic nuclei exhibit multiple energy scales ranging from hundreds of MeV in binding energies to fractions of an MeV for low-lying collective excitations. Describing these different energy scales within an ab-initio framework is a long-standing challenge. In this talk I will show how we overcome this challenge by using high-performance computing, many-body methods with polynomial scaling, and ideas from effective-field-theory. This progress enables us to address fundamental questions related to the how nucleons organize themselves in shell away from the valley of beta-stability, nuclear deformation and the limits of the nuclear chart, the role of meson-exchange currents and strong correlations in Gamow-Teller transitions, and the nature of the neutrino from computations of neutrino-less double beta decay and lepton-nucleus scattering on relevant nuclei. New ways to make quantified predictions are now possible by the development of accurate emulators of ab-initio calculations. These emulators reduce the computational cost by many orders of magnitude. This allows us to perform global sensitivity analysis, and use novel statistical tools to make quantified predictions for the neutron skin in 208Pb, the binding energy of exotic 28O, and what drives deformation in neon and magnesium isotopes. With this talk I hope to convey that the accurate computation of multiscale nuclear physics demonstrates the predictive power of modern ab initio methods.

Sixty plus years ago parity violation by the weak force was demonstrated in experiments led by Chien-Shiung Wu on the asymmetry of electron currents emitted in the beta decay of polarized 60Co. The asymmetry reflects two broken symmetries – mirror reflection and time-reversal, the latter imposed by an external magnetic field. The same year Bardeen, Cooper and Schrieffer published the celebrated BCS theory of superconductivity, and soon thereafter P. W. Anderson and P. Morel proposed that the ground-state of liquid 3He (the light isotope of Helium) was possibly a BCS superfluid exhibiting spontaneously broken mirror reflection and time-reversal symmetries. Indeed superfluid 3He-A, discovered in 1972, is the realization of a quantum state of matter that violates both parity and time-reversal symmetry. Definitive proof of broken mirror symmetry in 3He-A came 41 years later from the observation of asymmetry in the motion of electrons in superfluid 3He-A.1 I discuss these and related discoveries, as well as the physics underlying anomalous electron transport in such quantum systems with broken mirror and time-reversal symmetries.2,3

H. Ikegami, Y. Tsutsumi, & K. Kono, Chiral Symmetry in Superfluid 3He-A, Science, 341,59–62, 2013.
O. Shevtsov & J. A. Sauls, Electrons & Weyl Fermions in Superfluid 3He-A, Phys. Rev. B, 94, 064511, 2016.
V. Ngampruetikorn & J. A. Sauls, Anomalous Thermal Hall Effect in Chiral Superconductors, PRL 124, 157002 (2020).
† Research supported by NSF grant DMR-1508730.

The Large Hadron Collider at CERN is a two-beam proton synchrotron with a design energy per proton beam of 7 Tera-electron volts. It has been operating at CERN since 2010, with the high-profile success of finding the Higgs boson in 2012, thus completing the standard model of particle physics. The collider has been running since, and now preparations are being made to upgrade the collision rate (luminosity) of the proton collisions through the HL-LHC project. This upgrade will permit high precision measurements and more sensitive particle searches and involves considerable accelerator upgrade. This talk will review the LHC accelerator, the luminosity upgrade and present some of the UK’s contributions to this project. Following this, several public engagement projects linked to the LHC are presented, which attempt to communicate the science of the LHC to a range of diverse audiences, using a range of diverse methods.

Previous measurements of the anomalous magnetic moment of the muon have shown a sizeable discrepancy with standard model calculations, which might be indicative of new physics. We present a new measurement from the Fermilab Muon g-2 experiment with twice the precision of our prior result.

Plato is quoted as saying “If you do not take an interest in the affairs of your government, then you are doomed to live under the rule of fools.” Scientists have long been underrepresented in seats of political power. The 117th Congress had only one physicist, one chemist, and one geologist. In my talk I will discuss what it is like transitioning from being a scientist managing maintenance on the Spallation Neutron Source at the Oak Ridge National Laboratory to a career in local and state politics, and how my scientific training has aided my decision making.

Particle interactions create static and dynamic correlations even in seemingly disordered systems, and such correlations determine the properties, for instance through the fluctuation-dissipation theorem. Thus, figuring out such correlations is the key to understanding dynamic aperiodic matter (DAM), such as liquid, glass and itinerant electrons (Fermi liquid). However, correlations are often concealed and hard to detect by experiments, making the studies difficult, but interesting. I discuss two recent breakthrough examples by my research group, one on the glass transition and the other on the high-temperature superconductivity (HTSC). These two appear totally disconnected, but actually similar experimental approaches to dynamic correlation, the dynamic pair-distribution function determined by neutron/x-ray scattering or by simulation, brought us to the goal. In the case of the glass transition the discovery of density wave instability in liquid was the key [1], and for the HTSC the crucial step was the recognition that the electron dynamics affects electron correlation and the Bose-Einstein condensation [2].

1. T. Egami and C. W. Ryu, Frontiers in Materials, 9, 874191 (2022); J. Phys: Condens. Matter, 35, 174002 (2023).
2. T. Egami, Physica C, 613, 1354345 (2023).

In the simplest electroweak nuclear reaction, the proton-proton fusion process, two protons combine into a deuteron while emitting a positron and a neutrino. It is the starting point of the chain of fusion reactions that generate the sun’s energy. Only effective field theory can provide a high precision, first principles description of this process needed for modern stellar models. Such a calculation requires not only the nuclear interaction but also electroweak one- and two-body currents derived in a consistent effective field theory framework. I will review the effective field formalisms used to describe this process. I will explain how it depends on fundamental electroweak two-nucleon properties, and how these can be measured in complementary experiments. I will also discuss how the same tools as in proton-proton fusion can be used to describe electroweak processes involving so-called halo nuclei consisting of a tightly bound core and weakly bound valence nucleons.

The continuing development of production and separation techniques allowing for the study of nuclei far away from the line of stability has spurred the low energy nuclear field for the past three decades. Large proton-neutron imbalances drive emerging exotic phenomena such as shape coexistence or halo distributions of nuclear matter, which in turn have helped refine our understanding of the nuclear interaction in the nuclear medium. In this talk I will discuss our experimental efforts using beta-delayed gamma and neutron spectroscopy to characterize the nuclear structure of neutron rich nuclei around doubly magic 132Sn. In particular I will concentrate in the role nucleon excitations across shell closures play in all three regions, driving both increasingly smaller decay-half lives and larger neutron branching ratios.

The Quantum Science Center is a National Quantum Information Science Research Center headquartered at Oak Ridge National Laboratory. The purpose of the center is to discover and innovate in the field of quantum information science (QIS) to ensure American scientific leadership, economic competitiveness, and national security. QSC addresses this mandate by targeting three major scientific challenges 1) quantum simulation platforms for scientific discovery applications, 2) quantum sensing for real-world applications, and 3) topological quantum materials for new quantum devices. This talk will give an overview of the center’s scientific goals as well as highlights of recent scientific impacts and their outcomes in each of these areas.

Join us as we honor outstanding students, faculty, and staff at the annual UT Physics Honors Day celebration.

The merging of two neutron stars is a true multimessenger event that includes gravitational waves, an electromagnetic signal, and the emission of enormous numbers of neutrinos. In order to understand these signals we need a careful accounting of the microphysics that occurs during and after the merger. I will focus on the elements produced in these objects and the effect of two aspects of this microphysics; nuclear models/reactions and neutrino flavor transformation physics. In particular, I will discuss the importance of new developments in these areas to predictions of r-process observables and the astrophysical origin of the r-process.

The CERN Large Hadron Collider (LHC) has discovered the Higgs boson and confirmed the predictions for many of its properties given by the “Standard Model” of particle physics. However, this does not mean that particle physics is solved. Mysteries that the Standard Model does not address are still with us and, indeed, stand out more sharply than ever. To understand these mysteries, we need experiments at still higher energies. In this colloquium, I will argue that we should be planning for a particle collider reaching energies of about 10 times those of the LHC in the collisions of elementary particles. Today, there is no technology that can produce such energies robustly and at a reasonable cost. However, many solutions are under study, including colliders for protons, muons, electrons, and photons. I will review the status of these approaches to the design of the next great energy-frontier accelerator.

Majorana zero modes are fermion-like excitations that were originally proposed in particle physics by Ettore Majorana and are characterized as being their own anti-particle. In condensed matter systems, Majorana zero modes occur as fractionalized excitations with topologically protected degeneracy associated with such excitations. For over a decade, the only candidate systems for observing Majorana zero modes were the non-Abelian fractional quantum Hall state and chiral p-wave superconductors. In this colloquium, I will start by explaining the basic ideas of topological quantum computation using Majorana zero modes. This will be followed by a status update on transport experiments on potential Majorana systems including the recent experiments on Microsoft as well as those in iron superconductors. I will then provide a more detailed explanation of braiding, Majorana operators, and the associated topological degeneracy. I will end with my outlook on the challenges and future directions.

Long-baseline neutrino oscillation experiments present some of the most compelling paths towards beyond-the-standard-model physics through measurement of PMNS matrix elements and observation of the degree of leptonic CP violation. State-of-the-art long-baseline oscillation experiments, like NOvA and T2K, are currently statistically limited, however uncertainty in neutrino-nucleus scattering represents an important source of systematic uncertainty in future experiments like DUNE and Hyper-Kamiokande. Neutrino cross-section uncertainties can be reduced through high-statistics measurement of neutrino interactions on light nuclei, but creating a detector with an appropriate light target has proved elusive since the hydrogen bubble chambers designed in the 70’s. Modern bubble chamber-based dark matter detectors like PICO and the Scintillating Bubble Chamber have demonstrated that advances in sensor technology, computing, and automation would allow a modern bubble chamber to fully utilize the megawatt scale intensity LBNF beam. This talk will review the broad physics program and the construction of a hydrogen bubble chamber for use with neutrinos at Fermilab.

This talk discusses two examples of how a combination of analytical and computational methods can serve to connect basic theoretical ideas about correlated states to quantum information quantities and neutron scattering experiments. The ground state of a chain of antiferromagnetically interacting spins (the 1D “Heisenberg model”) is one of the solvable hydrogen atoms of many-body physics, but its dynamics remained opaque for eighty years. We introduce the Heisenberg model’s novel fluid-like dynamical regime at high temperatures and describe its realization in a variety of recent experiments ranging from neutron scattering on crystals to optical lattice emulation with atoms. It turns out that the dynamics of spins in this canonical model are described by the Kardar-Parisi-Zhang dynamical universality class, which is well known from classical problems such as driven interfaces. For frustrated systems in higher dimensions, controlled comparisons between theory and experiment are more difficult except for a small number of tractable cases. We forge ahead nevertheless and present theoretical arguments that a chiral spin liquid is likely to appear near the Mott transition in some triangular lattice materials, and second, that other kinds of spin liquids and quantum critical points are suggested in recent experiments.

In my talk, I review recent and not so recent works aiming to understand whether a nominally repulsive Coulomb interaction can give rise to superconductivity. I discuss a generic scenario of the pairing, put forward by Kohn and Luttinger back in 1965, and briefly review modern studies of the electronic mechanisms of superconductivity in the lattice systems, which model cuprates, Fe-based superconductors, and even doped graphene. I show that the pairing in all three classes of materials can be viewed as a lattice version of Kohn-Luttinger physics, despite that the pairing symmetries are different. I discuss under what condition the pairing occurs and rationalize the need to do renormalization-group studies. I also discuss most recent work on the pairing near a quantum-critical point, particularly the interplay between superconductivity and non-Fermi liquid physics.

Quantum materials provide responses and states of matter with no classical analogues. As such they offer opportunities to create an array of platforms for future devices crucial to human health, energy efficiency, communications and imaging. I will begin by describing the physics challenges and sensing opportunities these materials offer. I will then focus on our use of the relativistic electrons in graphene for biosensing. Specifically we have developed a new platform for multiplexed, rapid, easy to use detectors of biological analytes. I will discuss the unique aspects of graphene involved resulting in our demonstration of the detection of antibiotic resistant bacteria, decease biomarkers in saliva, opioids in waste water and respiratory infection at clinically relevant levels. Time permitting I will explain our efforts to use quantum materials to create new quantum simulators.

Neutron star mergers are connected to some of the most pressing open questions in physics and astrophysics, ranging from the nature of strong gravity, to the behavior of QCD in the non-perturbative regime, to the origin of the heavy elements. Multimessenger observations of these events hold the key to unlock these mysteries. However, theory is needed to turn data into answers. In this talk, I will discuss our efforts to model binary neutron star mergers in numerical relativity. I will talk about new developments in the simulation technology and I will present some recent results. Finally, I will talk about challenges and prospectives in this field.

Although Dark Matter (DM) comprises most of the mass of the Universe, the physical nature of DM remains unknown. The hypothesis that DM made of heavy Super Symmetric particles was refuted by LHC. Very light DM candidates axion cannot be found after several decades of searches. Direct searches for DM lack any signal of heavy and light DM particles. We will discuss a model where dark matter particles are a twin-copy of our ordinary particles with the same masses, charges, spins, interactions, thus forming similar atoms, molecules, planets, stars, etc. These DM particles are separated from us by small extra dimension, which makes them invisible for us but does not exclude their gravitational interaction with ordinary matter and between themselves. Such a model of Dark Matter was named a Mirror Matter model. Neutral particles in the ordinary and mirror worlds can be mixed with each other via extra dimensional tunneling and form, in this way, an “interaction portal” between two worlds. Thus, the neutron of our world (n) can be mixed with the mirror neutron (n’) leading to quantum-mechanical transformations n -> n’ and n’ -> n, the process called oscillations. Interaction of neutron components with the environment in both worlds (magnetic field, matter gas) might lead to the observable and reproducible effects that we will addressed in this talk. Some controversial observations pointing to the possible presence of the mirror neutron effects and results of the first searches for “mirror neutrons” will be discussed.

Detection of ultrahigh energy (UHE) neutrinos is key to identifying the most energetic objects and processes in the universe. These are the sources of UHE cosmic rays, which have been detected at earth with energies exceeding 1 Joule per nucleon (roughly the kinetic energy of a bird in flight). As UHE cosmic messengers, neutrinos are unparalleled for their ability to travel from source to Earth, interacting only weakly with matter and therefore able to traverse great distances unimpeded. For this same reason, however, they are very difficult to detect (and additionally at high energies, a vanishingly small number arrive at earth).

In this talk, I will discuss the general challenges in detecting UHE neutrinos, and the extensive experimental work that has been done so far to meet these challenges using various detection strategies. I’ll focus on a forthcoming experimental effort, the Radar Echo Telescope (RET), which uses well-known radar technology to attempt detection of the cascade produced by these elusive neutrinos as they interact in polar ice. I’ll discuss the theory and storied history of astroparticle physics, the radar echo method, recent laboratory work, and our current experimental efforts in service of UHE neutrino detection with RET.

Using circularly-polarized light to control quantum matter is a highly intriguing topic in physics, chemistry and biology. Previous studies have demonstrated helicity-dependent optical control of spatial chirality and magnetization M. The former is central for asymmetric synthesis in chemistry and homochirality in bio-molecules, while the latter is of great interest for ferromagnetic spintronics. In this paper, the authors report the surprising observation of helicity-dependent optical control of fully-compensated antiferromagnetic (AFM) order in 2D even-layered MnBi2Te4, a topological Axion insulator with neither chirality nor M. They demonstrated helicity-dependent optical creation of AFM domain walls by double induction beams and the direct reversal of AFM domains by ultrafast pulses. The control and reversal of AFM domains and domain walls by light helicity have never been achieved in any fully-compensated AFM. To understand this optical control, the authors studied an AFM circular dichroism (CD) proportional to the AFM order, which only appears in reflection but is absent in transmission. They showed that the optical control and CD both arise from the optical Axion electrodynamics. The Axion induction provides the possibility to optically control a family of PT-symmetric AFMs such as Cr2O3, even-layered CrI3 and possibly pseudo-gap state in cuprates. In MnBi2Te4, this further opens the door for optical writing of dissipationless circuit formed by topological edge states.

Who Ordered That? I.I. Rabi asked this question when a new particle, the muon, was discovered in 1936. Ever since, this unexpected particle has constantly brought us more surprises, including the pion discovery, parity violation, J/psi discovery, neutrinos and flavor physics etc., opening an avenue in front of us to new physics and new technology. In this talk, I will discuss a new aspect — a high energy muon collider. Due to the recent technological breakthroughs for muon cooling, the muon collider program has regained its momentum. I will present the idea and the current status for a muon collider, and discuss the rich physics potential in exploring the physics beyond the Standard Model, for two representative scenarios: the Higgs factory for the resonant Higgs production and the multi-TeV muon collider at the energy frontier.

Ineffective use of antibiotics leads to treatment failure and emergence of antibiotic resistance. One major challenge in the field is that our understanding of bacterial response to antibiotics is limited. The research in my lab focuses on quantitatively understanding the effects of antibiotics on bacterial cells and the population. In this talk, I will discuss our on-going research on stochastic population dynamics of bacteria treated with antibiotics. I will present our data that bacterial clearance does not follow a deterministic course but is highly probabilistic. These population fluctuations may be manipulated to facilitate bacterial eradication.

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Experiments with slow neutrons can address interesting scientific questions in nuclear/particle/astrophysics and cosmology. I will present a few examples of issues and experiments from this subfield of scientific activity.

The last several years have seen scientists being called upon to offer advice and recommendations with regards to several “crises” that have been impacting both the United States and the world at large. How has the role that science and scientists played been perceived? Science also plays a larger role in the lives of citizens. Examples being in nano-technology, human genomics, modified food crops, and fracking to name several. How should scientists respond to requests for advice and/or solutions? Are there any problems or pitfalls in the process of advising and forming policy?

CERN’s Large Hadron Collider has officially embarked on Run 3 after a multi-year shutdown, providing collisions at higher center-of-mass energy and enabling a more efficient delivery of data to the detectors. In this talk I will describe what we hope to learn from Run 3 and future runs of the LHC at the ATLAS Experiment, and the innovations that are helping us make forward progress in our understanding of the fundamental particles of the universe and the forces between them.

Fermions and bosons are fundamental realizations of quantum statistics, which governs both the symmetry of the wave function under the interchange of particle coordinates and the probability for two particles being close to each other spatially. Anyons in the fractional quantum Hall effect are an example for quantum statistics intermediate between bosons and fermions. Two recent experiments have provided evidence for such exotic anyonic statistics: the collision of anyons in a mesoscopic setup has demonstrated that anyons indeed have a reduced spatial exclusion as compared to fermions, and the symmetry of the quantum mechanical wave function for anyons has been measured directly by braiding anyons around each other in a Fabry-Perot interferometer. I will focus on the theoretical description of anyon collisions, which provides an interesting application of non-equilibrium bosonization.

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The first detection by the Laser Interferometer Gravitational Observatory (LIGO) of gravitational waves from merging black holes 1.3 billion light years away opened a new window on the Universe. The detection occurred nearly one hundred years after the publication of Einstein’s theory of general relativity (gravity), which predicted the existence of such waves, though Einstein himself doubted their existence and that we would ever be able to detect them. Three primary sources of gravitational waves detectable by LIGO are black hole mergers, neutron star mergers, and core collapse supernovae. Gravitational waves from the first two sources have been detected but not from the last. The last source will be the quintessential multi-messenger source, detectable for a Galactic event in gravitational waves, neutrinos, and photons across the electromagnetic spectrum. What we will learn from such a detection will depend on the sophistication of our core collapse supernova models. The UT–ORNL supernova group is well positioned to provide theoretical input to the gravitational wave astronomy community, in general, and the LIGO Scientific Collaboration, in particular, as we prepare for this watershed event. I will begin with a brief introduction to Einstein’s theory of gravity, without which the concept of a gravitational wave cannot be understood. I will then discuss gravitational waves and past milestone events in which they were detected from each of the first two sources listed above. Results from efforts by the UT–ORNL supernova group to predict core collapse supernova gravitational waveforms will be presented, as well as their implications for detection and culling from a detection information about the supernova central engine. I will then conclude and provide my outlook on the field.

One of the scientific frontiers in quantum magnetism is the discovery and understanding of quantum entangled and topologically ordered states in real bulk materials. At the focal point of the experimental investigation of these quantum spin networks is the identification of fractionalized excitations in transport and spectroscopic measurements. Inelastic neutron scattering has proved a powerful technique to reveal such signatures in a variety of systems ranging from quasi-1D magnets to kagome compounds and more. Recent and on-going developments with neutron scattering instrumentation have allowed the characterization of magnetic excitations in entire volumes of momentum-energy space with high resolution. I this talk, I will discuss how triangular-lattice antiferromagnets, in several different shape and forms, are an ideal testbed for many-body physics. This work was supported by DOE/BES under award DE-SC-0018660 and NSF under award DMR-1750186.

Lattice QCD was invented in 1973-74 by Ken Wilson, who passed away in 2013. This talk will describe the evolution of lattice QCD through the past almost 50 years with particular emphasis on its first years, and on the past two decades, when lattice QCD simulations finally came of age. Thanks to theoretical breakthroughs in the late 1990s and early 2000s, lattice QCD simulations now produce the most accurate theoretical calculations in the history of strong-interaction physics. They play an essential role in high-precision experimental studies of physics within and beyond the Standard Model of Particle Physics. The talk will include a non-technical review of the conceptual ideas behind this revolutionary development in (highly) nonlinear quantum physics, together with a survey of its current impact on theoretical and experimental particle physics, and prospects for the future.

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Discovered in 1986, the cuprate superconductors hold the record for highest superconducting transition temperature (139 K) under ambient pressure. These quasi two-dimensional materials are structurally and electronically very complex, and so is the origin of their spectacular superconducting properties. In this talk, I’ll review some key physical aspects of these materials and show how these insights can be applied successfully to establish two-dimensional superconductivity on the simplest and most ubiquitous electronic materials platform: Silicon. By decorating a p-type Si(111) surface with a dilute monatomic tin layer, we constructed a chiral d-wave superconductor with a critical temperature of up to 9 Kelvin and an upper critical field in excess of 15 Tesla. Chiral d-wave superconductivity is a very rare and exotic state of matter that is characterized by broken time-reversal symmetry and the presence of co-propagating edge modes that are potentially interesting for topological quantum computing. The simplicity and experimental control of simple adsorbate systems may provide a powerful testbed for theoretical models and discovery of elusive phases of quantum matter.

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The first exascale computer, called Frontier, has been delivered to Oak Ridge National Laboratory this past year. This unique scientific instrument is the culmination of more than a decade of concerted effort. I will relate a bit of the history of hybrid-node computing at the Oak Ridge Leadership Computing Facility (OLCF) and how Frontier represents the latest iteration of that approach. Some details of Frontier’s architecture will be discussed, including an overview of the new AMD GPUs that provide the bulk of the computational power for Frontier. Finally, we will take a look at some physics problems that will benefit from the increased capability at exascale, including the last great classical physics problem of turbulence. I will pay particular attention to the effects of turbulent mixing on the explosion mechanism of thermonuclear supernovae, a problem we recently studied on Frontier’s predecessor, Summit.

Slides

At energy densities above about 1 GeV/fm^3 QCD predicts a phase transition in nuclear matter to a plasma of quarks and gluons. This matter, called a Quark Gluon Plasma (QGP), has different properties from normal nuclear matter due to its high temperature and density and can be created in high energy nuclear collisions. Measurements at the Relativistic Heavy Ion Collider (RHIC) on Long Island and the Large Hadron Collider (LHC) in Geneva allow studies of nucleus-nucleus collisions over two orders of magnitude in center of mass energy. I will discuss how we can measure the properties of the QGP, even though the liquid produced in these collisions only lives around 10^{-23} seconds, and how we get the most out of those data. I will also discuss incorporation of undergraduates in these studies in a Course-based Undergraduate research experience (CURE). This provides a valuable educational experience for undergraduates while also assisting collaborations and the field with data preservation and comparisons to models. CUREs are a useful tool for increasing research opportunities in the department, increasing diversity in the field, and improving retention in the major.

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While the rise of quantum computers may one day help solve complex problems and deliver information with unhackable security, there is lack of a material platforms for scalable realization of quantum technologies. For instance, the most interesting magnetic property of the celebrated quantum spin liquids (QSLs) is the possibility of quantum mechanical encryption and transport of information, protected against environmental influences. Despite extensive studies on QSLs, they are still far away from applications. First obstacle is simply the shortage of real examples of QSL systems. Second obstacle is that most of the studied QSLs are insulators and electronically inert, which is incompatible with an electrical circuit that relies on moving charge carriers. The grand challenge is to find a way to convert the entanglement information into mobile charge signal by “metallizing” quantum magnets.

In this talk, I will introduce a unique approach by using strategical materials design focusing on geometrically frustrated magnets to address these two obstacles. First, we search for QSL in new spin-1/2 triangular lattice antiferromagnets. The two examples are Na2BaCo(PO4)2 and YbMgGaO4. Second, we explore how to electronically detect the spin sates and spin excitations in newly designed heterostructures based on pyrochlore lattice. The two examples are Dy2Ti2O7/Bi2Ir2O7 and Yb2Ti2O7/Bi2Ir2O7.

I will also introduce the crystal growth techniques used to synthesize these systems since the materials growth is the starting point of materials research and the high quality samples are essential to learn their intrinsic properties.

Slides

Understanding the physics of the high-temperature superconducting cuprates remains a grand challenge for condensed matter physics. The central difficulty here is that the cuprates host a rich set of novel magnetic and charge correlations that can compete/cooperate with superconductivity in ways that are not yet fully understood. In recent years, state-of-the-art nonpertubative numerical calculations for the single-band Hubbard model, a minimal model for the cuprates, have observed similar behavior with several nearly degenerate states closely competing for the ground state. This talk will discuss such numerical studies, including our recent work accessing these physics in the thermodynamic limit, where we find evidence for novel pair-density-wave correlations intertwined with the stripe correlations. I will also discuss how perturbations like the electron-lattice interaction can alter the balance between these competing orders.

Much of what we know about high-energy components of nuclear structure comes from recent measurement campaigns at Jefferson Lab. Experiments from the 6 GeV era have provided precise results about short-range nucleon-nucleon correlations and their nuclear dependence. Additionally, an intriguing correlation was observed to measurements of modifications of nuclear quark distributions (EMC effect). I will highlight key insights gained from previous measurements (including recent ones) and present future experiments aimed at further illuminating these exotic components of nuclear structure.

Astronomers now know that supermassive black holes are in nearly every galaxy. Though these black holes are an observational certainty, nearly every aspect of their evolution — from their birth, to their fuel source, to their basic dynamics — is a matter of lively debate. Fortunately, LISA, a space-based gravitational wave observatory set to launch in 2034, will revolutionize this field by providing data that is complementary to electromagnetic observations as well as data in regimes that are electromagnetically dark. This talk will touch on our current understanding of how SMBHs form, evolve, and alter their galaxy host, and will outline the theoretical, computational and observational work needed to make the most of LISA observations.

The LHC collider and its experiments have been successful in their effort to complete the Standard Model of particle physics through the discovery of the Higgs Boson. Measurements have been made in a variety of Standard Model production and decay modes. However, the currently funded colliders and experiments still leave a number of important measurements out of reach. Several attractive future collider concepts, which are potentially feasible to be constructed in the US or abroad in the next 10-30 years, are being considered during the Snowmass planning study. These are intermediate-scale and compact collider projects that could prove to be cost-effective and timely, and help advance particle physics beyond the HL-LHC goals. We discuss these collider proposals and the prospect of Higgs measurements at the future experiments.

Since the Bronze Age, humans have been manipulating, designing and optimizing materials to fit our needs. The advent of quantum mechanics in the early 1900s gave us the foundation to understand how a material’s properties stem from its constituent fundamental particles and how these properties can be manipulated. After nearly a century, computational tools based on quantum mechanics possess the accuracy to characterize materials in silico, in effect running virtual experiments, before they are ever synthesized. In order to direct the search for novel functional materials, insights from these calculations can be used to develop design rules. In this talk I will present results on a variety of perovskites, an extremely versatile class of materials exhibiting a wide range of function properties with the chemical formula ABX . First, I will discuss properties that stem from the crystal structure, focusing on ferroelectricity, along with a recent method we have developed to identify stable structures and its application in barium titanate (BaTiO ) — the prototypical ferroelectric perovskite. Second, I will discuss the ability of the rare-earth nickelates (RNiO ) to localize charge when doped at high concentrations leading to a reversible metal- or semiconductor-to-insulator transition. I will discuss experimental and computational results that demonstrate how these materials can be tailored for a number of potential applications from solid-state electrolytes to ferroelectrics.

Kagome metals are compelling materials platforms for hosting electronic states that feature an interplay between topologically nontrivial electronic states and correlated electron phenomena. These two features can, for instance, arise from the Dirac points, flatbands, and saddle-points endemic to the band structures of kagome networks. States featuring orbital magnetism and unconventional superconductivity are predicted to arise at select fillings, in particular within systems where the saddle-points are located close to the Fermi level. In this talk I will present some of our recent work exploring the electronic properties of two new classes of kagome metals, each with Z2 topology and saddle points close to Fermi energy. Specifically, our work studying the compounds AV3Sb5 (A=K, Cs, Rb) and RV6Sn6 (R=rare earth ion) will be presented. The former family of compounds exhibit an unusual charge density that shows hints of time-reversal symmetry breaking intertwined with a low temperature superconducting ground state. The latter family provide a tunable platform for interfacing magnetic order and frustrated magnetic interactions with a topologically nontrivial kagome band structure. Unconventional electronic properties observed in each class of these new kagome compounds and open questions will be discussed.

Neutrons, photons, and electrons are the three most common probes used to determine the structure and dynamics of materials. So, what is the advantage of using neutrons? In this presentation, I will describe how and why neutrons are used to understand topics as diverse as Li-ion conductivity in battery materials, strain evolution in 3D-printed structures, the binding between drug molecules and proteins, heat transport in thermoelectrics, and magnetic excitations in quantum materials. I’ll show examples from the two neutron sources at Oak Ridge National Laboratory: the High Flux Isotope Reactor (HFIR) and the Spallation Neutron Source (SNS), and I’ll describe the different characteristics of each source.

In this talk I will introduce the recently developed concept of higher order topology and discuss realizations of higher order topological insulator phases in quantum materials and in analog engineered materials such as photonic crystals, microwave resonator arrays, and circuit resonator arrays. I will first present a broad overview of condensed matter physics and the role topology plays in this context, which I hope will appeal to a diverse, non-expert audience. For the second half of the talk I will move on to more recent theoretical and experimental developments which include the prediction and experimental discovery of higher order topological insulators. Finally, I will highlight the interplay between topology and geometry by illustrating the sensitivity of higher order topological insulators to crystalline defects such as disclinations, and partial dislocations.

In the past year, several projects probing for particle physics beyond the “Standard Model” with low energy neutrons have made important progress. In these experiments, neutrons with average energies ranging from room temperature to only a few milli-Kelvin are used to perform high precision measurements sensitive to new physics. This colloquium will concentrate on two experiments: a measurement of the neutron lifetime called UCNtau and an interferometry project measuring waves diffracted from a thick, “perfect” Si crystal. UCNtau, an experiment at the Los Alamos Neutron Science Center, recently reported the most precise measurement of the neutron lifetime to date. Although the neutron lifetime has been measured with increasing precision many times over the past 70 years, it remains the focus of considerable interest both for its impact in probes for new physics and for the role it plays in defining our knowledge of the weak nuclear force. UCNtau determines the neutron lifetime by storing very low energy (ultracold) neutrons in a roughly 1 meter diameter bowl lined with permanent magnets, where they bounce off the magnetic fields in the bowl, and are prevented from escaping through the top of the trap by gravity. The motivation (which includes an ongoing experimental puzzle), recent progress and plans for an upgrade of UCNtau will be presented. The second project measures an interference pattern resulting from “pendellosung,” where a neutron beam undergoing diffraction in a (vey nearly ideal) Si crystal produces an observable oscillatory signal in the intensity of the transmitted beam. This oscillatory provides a remarkably precise measurement of the potential experienced by the neutron, permitting a high precision test of the expected interactions of the neutron with the Si lattice. Results from an experimental campaign to measure neutron pendellosung in Si at the Neutron Interferometry and Optics Facility at the National Institute of Standards and Technology will be presented, providing new limits for gravity-like short-ranged forces and insight into the properties of the neutron and the properties of Si crystals.

We know from everyday life that depending on the external conditions, a large collection of atoms organizes itself into a solid, liquid, or gas phase. But how does a large number of interacting electrons (a situation frequently encountered in solid state systems) collectively behave? How does electronic matter respond to external electric and magnetic fields? Systems where these questions are difficult to answer are those where the correlations between electrons are strong, which is the case for unconventional high temperature superconductors and quantum magnets. Using examples of real materials and toy models, I show that such strongly correlated systems harbor a rich panoply of phases, which include “valence-bond solids,” “quantum spin liquids,” and “Fermi gases,” and require us to embrace concepts such as “fractionalization” and “topological order.” In the second part of the talk, I will focus on our investigations of frustrated magnetic materials (such as those on the kagome and pyrochlore geometries) that are fertile hunting grounds for novel phases of quantum matter. Frustration arises when multiple spatial arrangements of electron spin orientations each have similar collective energy, so there is no clear winner. I will discuss recent exciting experimental and theoretical developments in equilibrium and nonequilibrium dynamics that are enabling a comprehension of how such magnetic systems thermalize or act glassy (in the absence of disorder) in different situations. I conclude with stating some theoretical challenges that need to be addressed to achieve a more complete understanding of strongly correlated electronic matter.

Hanno Weitering and ECC Members

One of the motivations for the recent upgrade of Jefferson Lab was to precisely explore the connection between the fundamental quarks and gluons of Quantum Chromodynamics (QCD)- the accepted theory of the strong force – and the effective hadron descriptions of the strong interaction. The ultimate goal being an accurate understanding of the emergence of nuclei from QCD. The key experiments of this program typically aim to study fundamental QCD prediction in nuclei, in search of the onset of these phenomena. Many of the early experiments that have been completed at the upgraded JLab are part of this program designed to address the connection between quarks and nuclei. We will discuss some puzzling new results from the search for squeezed protons and the onset color transparency, a rigorous prediction of QCD. We will also highlight some upcoming experiments.

Design Thinking is a human-centered (empathy-based) method of creative inquiry used to transform current conditions into preferred ones. Focus is on developing novel or innovative outcomes when conventional solutions are no longer relevant. Design thinking can be used in an array of disciplines and applications such as developing curricula and new courses, medical equipment, software, policies, and institutional structures. This introductory presentation is for all people interested in the learning processes of creative inquiry from a human-centered perspective.

After two successful runs of the Large Hadron Collider (LHC), the experimental verification of the particle content of the Standard Model (SM) has been completed with the discovery of the Higgs boson, and so far all searches for beyond-SM physics have resulted in exclusion limits. However, the data collected and analyzed so far is only 5% of the total foreseen until ~2040, and the absolute majority will be delivered by the upgraded High-Luminosity LHC which will explore the energy frontier during the 2030s. I will present an overview of the substantial upgrades of the ATLAS and CMS experiments for the HL-LHC that are currently underway, and the expected sensitivities for selected physics topics. As collider facilities like the LHC used by the global particle physics community take decades to design, construct, and commission, large community planning efforts (like Snowmass in the US) are currently evaluating several options for future colliders as well, and I will also discuss the main options under consideration.

It is often said, no one gets out of life alive. Equally true is the fact that no one gets out of graduate school without emotion and often physical stress. Since 1980, multiple studies and meta-analyses of mindfulness based clinical interventions have found moderate to strong effect sizes for treatment of anxiety and mood symptoms associated with serious health conditions as well as for individuals experiencing mood-spectrum disorders, stress, and anxiety without co-morbid health conditions. In this conceptual and experiential presentation, we will briefly review the research evidence supporting the health and mental health benefits of mindfulness practices and the neuroscience of mindfulness practices. Session participants will be introduced to a few brief mindfulness practices and given resources for future use. Finally, as this will be an audience of physicists, nonduality and interconnectedness will be touched upon. “Subject and object are only one. The barrier between them cannot be said to have broken down as a result of recent experience in the physical sciences, for this barrier does not exist.” – Erwin Schrodinger.

Why don’t we all drive electric cars? Does it really matter if you don’t recycle that plastic water bottle? If the Sun were made of gerbils, would the Earth be incinerated? How can we answer these questions without relying on experts? This talk will cover the principles of estimating, introduce the “Goldilocks” categories of answers, and then look at some of the big (and small) questions of our time, including: Paper or plastic? Gasoline or electric cars? Should we pee before flying?

Antihydrogen—the antimatter equivalent of the hydrogen atom—is a unique platform for testing fundamental symmetries. In particular, CPT symmetry (Charge, Parity and Time) requires that the spectrum of antihydrogen be identical to its ordinary matter cousin. In the ALPHA experiment at CERN, antihydrogen atoms are synthesized and magnetically trapped to enable precise measurements and comparison to hydrogen. Recently, we have measured the 1S-2S transition with a relative error of just 2 parts in a trillion—the most precise direct measurement on an antimatter system to date.

Einstein’s weak equivalence principle (WEP) provides another prediction for antimatter which has yet to be tested experimentally: that the gravitational acceleration of antimatter should be equal to that of ordinary matter. ALPHA-g is a new experiment which will measure this acceleration directly through careful release of magnetically trapped antihydrogen atoms and recording of their annihilation positions.

This talk will survey recent advances in van der Waals heterostructures formed by stacking two layers of atomically thin materials. When the two layers have a small lattice mismatch or rotational misalignment, a long-wavelength moire structure emerges, which can produce entirely new electronic structures and quantum states of matter. I will describe the emergence of chiral spin texture and quantum anomalous Hall effect in semiconductor moire heterostructures, and propose a potential application of moire metals in catalysis, in particular, the production of hydrogen from water.

The physics behind high-temperature superconductivity in cuprates remains a defining problem in condensed matter physics. Among the myriad approaches to addressing this problem has been the study of alternative transition metal oxides with similar structures and electron count. After a 30 year quest, a non-cuprate compound with a cuprate-like structure that exhibits superconductivity has been found: hole-doped NdNiO2. Given that this material is one of the members of a larger series of layered nickelates, this result opens up the possibility of finding a new family of unconventional superconductors. By means of electronic structure calculations, we have analyzed the similarities and differences between this family of low-valence planar nickelates and cuprates. Even though these nickel oxide materials possess a combination of traits that are widely considered as crucial ingredients for superconductivity in cuprates (a square-planar nature, combined with the appropriate 3d-electron count, and a large orbital polarization) they also exhibit some important differences (a larger p-d energy splitting, and lack of magnetism in the parent compounds). Our results show that low-valence layered nickelates offer a new way of interrogating the cuprate phase diagram and are singularly promising candidates for unconventional superconductivity.

Quantum fluids have provided a unique “laboratory” for the study of strongly interacting assemblies of particles obeying quantum statistics. In particular, superfluid 4He exhibits interesting quantum phenomena, such as Bose condensation, which has recently been observed in other systems such as dilute gases and excitonic systems. These liquids have also occupied a central role as a model system for the study of critical phenomena, and even the birth of the Universe.

Recent attention has focused on the effects of disorder, induced by confinement, which has a profound effect on the macroscopic properties of the superfluid. The microscopic dynamics are fundamental to developing a complete picture of these unique liquids and the changes induced by disorder. Inelastic neutron scattering provides a powerful probe of these microscopic excitations. I will discuss measurements of the confined superfluid which show that much of the new macroscopic behavior can be understood in terms of the appearance of new microscopic excitations.

We study how cellular memory influences the cell’s properties and restrict heterogeneity in future generations. Heterogeneity in physical and functional characteristics of cells proliferates within a population due to stochasticity in intracellular biochemical processes and in the distribution of resources during divisions. It is limited, however, in part by the inheritance of cellular components between consecutive generations. In this talk I will present our new study in which, we characterize the dynamics of (non-genetic) inheritance in the simple bacterial model organism E. coli, and reveal how it contributes to regulating the various cellular properties (size, growth rate, etc.) in future generations. This is achieved using a novel microfluidic device that enables us to measure how two sister cells become different from each other over time. Our measurements provide the inheritance dynamics of different cellular properties, and the ‘inertia’ of cells to maintain these properties along time, i.e. cellular memory. We find that cellular memory is property specific and can last up to ∼10 generations. Our results can uncover mechanisms of non-genetic inheritance in bacteria and help develop quantitative description of cell progression and variation over time.

Four decades ago, Richard Feynman envisioned that a main application of quantum computers will be “quantum simulation”, that is, the simulation of the dynamics of quantum systems. Quantum simulation is ubiquitous in science but appears to be beyond the reach of classical computers. Not surprisingly, a lot of research in quantum computing has gone into developing methods for quantum simulation, but significant advances in this field were demonstrated only recently. In this colloquium, I will describe the quantum simulation problem in detail. Starting from the basics of quantum computing, I will show how quantum algorithms are constructed and then present a summary of the best quantum simulation methods known to date. I will also discuss some open problems that must be addressed to push practical quantum simulation closer to reality.

Seventy years ago, two radio engineers emerged from the frenzy of World War II and entered the new field of radio astronomy. Robert Hanbury Brown and Richard Twiss developed an entirely new instrument and technique, based on “correlated noise,” to measure the angular radius of previously unresolvable stars. Initially greeted with skepticism, their work led directly to the birth of quantum optics. At nearly the same time, Goldhaber et al discovered a tiny unexpected correlation in the first true particle physics experiments; until recently, the “GGLP” effect played a minor role in particle physics. It would take another 15 years until the connection between these apparently disparate phenomena was realized by Shuryak and others around 1976, just as the new field of heavy ion physics was emerging. Thus did Hanbury Brown’s discovery give birth to femtoscopy, the most direct method to probe space and time at the scales of 1e-15 meter and 1e-22 second. I will discuss the structures and insights that femtoscopy has revealed in ultra-relativistic ion collisions at RHIC and the LHC and their role in establishing the hydrodynamic nature of the quark-gluon plasma.

If time permits, I will discuss current progress to bring a high-energy physics approach to telescope arrays and relaunch stellar intensity interferometry with fast digital electronics and massive computing.

Majorana particles are real solutions of the Dirac equation, representing their own antiparticles. In the condensed matter context, Majorana refers to electronic modes in nanostructures described by peculiar ‘pulled-apart’ wavefunctions and by hypothesized non-Abelian exchange. This last property makes them interesting for quantum computing. I will present our efforts to generate and verify Majorana modes in semiconductor nanowires coupled to superconductors. In particular, how can we tell Majorana signatures apart from similar Andreev states that do not have non-Abelian properties? While we may not have a verified Majorana observation now, I will talk about ways to get there: through careful experiments, improved nanowires and device fabrication and with eyes open for alternative explanations.

This presentation is designed to give an overview of the definition of mentoring and the mentoring process. Participants will learn about the significance of faculty mentoring, mentoring vs. advising, and mentoring relationships. Participants will also be introduced to the phases of mentoring, a mentoring model, and learning about the benefits of cross-cultural mentoring and network mentoring.

The keystone of the Standard Model of particle physics, the Higgs Boson, was discovered during the first run of the Large Hadron Collider (LHC). Outstanding questions in particle physics remain, however. Why does the Higgs boson have the mass that it does? What is the particle nature of dark matter? What might anomalous measurements in rare Standard Model processes be telling us? Supersymmetry remains one of the most promising theories for new physics accessible at the LHC which could address these questions, and there are many well-motivated ways it could have evaded detection thus far. In this talk, I will motivate the search for supersymmetry, and summarize the current status and outlook of searches for supersymmetric particles on the ATLAS experiment, with a focus on searches for supersymmetric particles with a long lifetime.

The confluence of fundamental symmetries (such as time reversal invariance) and relativistic quantum mechanics is known to produce emergent electronic states in crystalline solids that are accurately described using the language of topology. This talk provides an overview of this relatively young field of research, showing how the synthesis and study of topological quantum matter [1] yields a playground for both exotic pursuits at cryogenic temperatures (such as the study of axions [2], Majoranas [3], and skyrmions [4] in condensed matter) and spintronic technologies that work under ambient conditions [5- 7].

Nitin Samarth, “Quantum materials discovery from a synthesis perspective,” Nature Materials 16, 1068-1076 (2017).
Di Xiao et al., “Realization of the axion insulator state in quantum anomalous Hall sandwich heterostructures,” Phys. Rev. Lett. 120, 056801 (2018).
M. Kayyalha et al., “Absence of evidence for chiral Majorana modes in quantum anomalous Hall-superconductor devices,” Science 367, 64-67 (2020).
P. Li et al., “Topological Hall Effect in a Topological Insulator Interfaced with a Magnetic Insulator,” Nano Letters 21, 1108 (2021).
A. R. Mellnik, et al., “Spin-transfer torque generated by a topological insulator,” Nature 511, 449 (2014).
Hailong Wang et al., “Surface-State-Dominated Spin-Charge Current Conversion in Topological- Insulator–Ferromagnetic-Insulator Heterostructures,” Phys. Rev. Lett. 117, 076601 (2016).
Hailong Wang et al., “Fermi level dependent spin pumping from a magnetic insulator into a topological insulator,” Phys. Rev. Res. 1, 012014 (R) (2019).

My laboratory focuses on developing novel single-molecule imaging tools in live cells to probe various aspects of microbial cellular processes. We are broadly interested in understanding how the molecular constituents of bacterial cellular processes are spatiotemporally organized and what essential functions such organizations convey. In this talk I will discuss our recent work on the structure, function and dynamics of the bacterial cell division machinery. Using single molecule-based superresolution imaging in live E. coli cells, we first illustrated the structural organization of the bacterial cytokinesis ring formed by the tubulin homolog FtsZ protein. We next discovered that FtsZ uses its GTP hydrolysis to power treadmilling dynamics and function as a linear motor to transport sPG synthase enzymes along the septum through a Brownian-Rachet mechanism. Furthermore, we discovered that the activity of these enzymes are spatially regulated through their differential coupling to two distinct tracks along the septum. Our work redefines the role of the Z-ring in bacterial cell division and opens new directions to study the precise spatial coordination and regulation of the large ensemble of cell division proteins.

The rich physics associated with the emergence of technologically relevant quantum orders in materials stems from complex interaction of electronic charge, spin, and orbitals, and their coupling to the host lattice. In transition metal systems with partial filling of d-manifolds novel properties often engage the orbital sector. Systems exhibiting orbital degeneracy and/or electronic frustration imposed by their lattice topology are particularly interesting, as orbitals couple both to the spin, via electronic interactions, and to the lattice, via Jahn-Teller mechanisms. The removal of this orbital degeneracy and the subsequent relief of frustration then impact symmetry lowering and material properties. The electronic complexity of the low temperature ordered symmetry-broken states has been thoroughly studied in systems displaying diverse emergent behaviors such as frustrated magnetism, colossal magnetoresistivity, charge and orbital order, metal-insulator transition, pseudogap, and high temperature superconductivity. Their understanding employs Fermi surface nesting, Peierls, and band Jahn-Teller mechanisms, among others.

In systems where orbital degeneracies are anticipated, crystallographic symmetry lowering at the temperature driven structural phase transitions is often assumed to imply simultaneous orbital degeneracy lifting (ODL) by engaging some cooperative mechanism. Consequently, seemingly mundane high temperature regimes possessing high crystallographic symmetry remain much less explored. In contrast to this concept, recent utilization of probes sensitive to local symmetry qualified the ODL as a local electronic effect existing at temperature well above the global symmetry breaking transitions.

This presentation will showcase a sensitive local structural technique, x-ray atomic pair distribution function analysis, as it reveals the presence of fluctuating local-structural distortions at high temperature of several transition metal-based quantum materials exhibiting orbital-selective ground states. We argue that this hitherto overlooked fluctuating symmetry-lowering is electronic in nature, thereby modifying the energy-level spectrum and electronic and magnetic properties. The origin is a local, spatio-temporally fluctuating, orbital degeneracy lifted state, that acts as a precursor to electronic phenomena observed at low temperature. It will be demonstrated that such local orbital states come in many flavors (e.g. engaging single [1,2] or multiple transition metal d orbitals [3]), and that they are likely to exist both in the proximity to itinerant-to-localized crossover [1,3] and deep in the Mott insulating regime where charge fluctuations are suppressed [4]. These observations suggest that such precursor states are likely to be widespread amongst diverse classes of partially filled nominally degenerate d-electron systems, with potentially broad implications for our understanding of their properties.

[1] E.S. Bozin et al., Nature Comms. 10, 3638 (2019).
[2] R.J. Koch et al., Phys. Rev. B 100, 020501(R) (2019).
[3] L. Yang et al., Phys. Rev. B 102, 235128 (2020).
[4] R.J. Koch et al., arXiv:2009.14288 (2021).

Using the metaphor of a challenging mountain bike journey in the Smoky Mountains, learn about the key principles that will help you to learn (THINK, SPACE, TEST), stay motivated (GRIT, GROWTH MINDSET, SELF-CONTROL), be productive (CAPTURE, CLARIFY, PLAN), and still manage to have fun during your time at UTK.

The axion is a proposed particle whose existence might account for much of the dark matter of the universe. This same particle also arises as the solution to the strong-CP problem of particle physics. There have several decades of experiments that have attempted to detect new particles with many of the properties of the axion – but without being sensitive to the preferred region of parameter space. I will report on the Axion Dark Matter Experiment, ADMX, which is currently running and achieving the required sensitivity towards potential discovery.

As one of very few macroscopic manifestations of quantum coherence, magnetic order is at the crux of condensed matter physics. Assisted with neutrons, magnetism beyond ferromagnetism such as antiferro- ferri- and non-collinear magnetic order was integrated in our knowledge only in the last decades. Nowadays, our interest has been moved to topologically nontrivial magnetism and magnetically coupled multiferroic systems. Here I will introduce our recent observation using neutrons of a field-tunable toroidal moment in a chiral-lattice magnet. A toroidal dipole moment appears independent of the electric and magnetic dipole moment in the multipole expansion of electrodynamics. It arises naturally from vortex-like arrangements of spins. Observing and controlling spontaneous long-range orders of toroidal moments are highly promising for spintronics but remain challenging. Here we demonstrate that a vortex-like spin configuration with a staggered arrangement of toroidal moments, a ferritoroidal state, is realized in a chiral triangular-lattice magnet BaCoSiO4. Upon applying a magnetic field, we observe multi-stair toroidal transitions correlating directly with metamagnetic transitions. We establish a first-principles microscopic Hamiltonian that explains both the formation of toroidal states and the metamagnetic toroidal transition as a combined effect of the magnetic frustration and the Dzyaloshinskii-Moriya interactions allowed by the crystallographic chirality in BaCoSiO4.

Experiments using slow neutrons can address interesting scientific questions in particle physics/astrophysics/cosmology. In this talk I will concentrate specifically on slow neutron experiments which offer input into Big Bang Cosmology or which can search for some of the ingredients that may have led to the matter-antimatter asymmetry of the universe.

Feynman diagrams are the most celebrated and powerful tool of theoretical physics usually associated with an analytic approach. I will argue that diagrammatic expansions are also an ideal numerical tool with enormous and yet to be explored potential for solving interacting fermionic systems by direct simulation of connected Feynman diagrams. Though the original series based on bare propagators and interactions are sign-alternating and often divergent one can still compute the correct answer behind them by using appropriate series re-summation techniques, conformal mappings, asymptotic series analysis, and homotopic action tools. Ultimately, the diagrammatic expansion can always be made convergent! When dealing with Feynman diagrams, the conventional fermionic sign problem is simply absent for regular systems because the entire setup is valid in the thermodynamic limit. Instead, fermionic sign is a “blessing” because it leads to massive cancellation of high-order diagrams and ultimate convergence of the re-summed series. For illustration, I will discuss results for the unitary Fermi gas, the Fermi-Hubbard model, and jellium (homogeneous electron gas).

The established cosmic preponderance of baryons over antibaryons is usually regarded as evidence for baryon number violation, but we have as yet to discover anything of its nature. For example, baryon number B or the difference of baryon number and lepton number L, B-L, could be a gauge symmetry, and this symmetry may be explicitly or spontaneously broken or both. These ideas also thread through theoretical models of the neutrino mass and/or of dark matter. I will survey the possibilities, their connections and implications, emphasizing the suite of experiments that test the various scenarios of B violation and noting the constraints that also follow from the observed properties of neutron stars.

Design and discovery of new quantum materials will accelerate the development of new technologies in the future. I will report my group research progress in the past 4 years, mainly focusing on the new superconductors and new magnetic topological quantum materials. My group recently discovered several new superconductors. I will explain our interpretation of this work. More importantly, we are trying to use chemical bonding concept to predict the existence of superconductivity in the materials. Magnetic topological quantum materials (MTQMs) can give rise to forefront electronic properties such as the quantum anomalous Hall effect, axion electrodynamics and Majorana fermions. In our group, we used chemistry electron count rules and structure-property relationship to design new MTQMs. I will describe how to design and prove the material candidate as a new MTQM from both experimental and theoretical aspects and show how topological electronic states and magnetism interplay in the new material.