Colloquium Schedule Fall 2025
Monday, December 8, 2025
Speaker: Deyu Lu (Center for Functional Nanomaterials, Brookhaven National Laboratory)
Title: Resolving the Solvation Structure and Transport Properties of Aqueous Zinc Electrolytes from Salt-in-Water to Water-in-Salt Using Machine Learning
Abstract: ZnCl2 is one of the most soluble inorganic salts containing a multivalent cation. Molten ZnCl2 hydrates at high concentrations have incomplete first solvation shell and are referred to as water in-salt (WIS). Recently, ZnCl2 WIS electrolytes have shown improved performance compared with dilute electrolytes in aqueous zinc ion batteries. They suppress the water splitting reactions, help regulate the morphologies of Zn plating and improve the Coulombic efficiency of Zn anodes. Here, I report a joint computational and experimental study of the structural and dynamic properties of aqueous ZnCl2 electrolytes with concentrations ranging from salt-in-water (SIW) to WIS. By developing a neural network potential (NNP) model, we perform molecular dynamics (MD) simulations with ab initio accuracy but at much larger length and longer time scales. The NNP predicted structures are validated by the structure factors measured by X-ray total scattering and X-ray absorption spectroscopy experiments. The MD trajectories provide a comprehensive and quantitative picture of the Zn2+ solvation shell structures. We find that the O-H covalent bonds in water are strengthened with increasing salt concentration, thus expanding the electrochemical stability window of aqueous electrolytes. In terms of dynamic properties, the calculated and measured conductivities are in good agreement. Through the analysis of calculated cation transference number, we propose a three-stage charge carrier transport mechanism with increasing concentration: independent ion transport, strongly correlated ion transport, and small positive charge carrier diffusion through negatively charged polymeric clusters. Our study provides fundamental atomic-scale insights into the structure and transport properties of the ZnCl2 electrolyte that can aid the optimization and development of WIS electrolytes for battery applications
Host: Xifan Wu
Monday, December 1, 2025
Speaker: Charles W. Clark (Joint Quantum Institute, National Institute of Standards and Technology and University of Maryland, and ScienceCast, Inc.)
Title: From the neutron bouncing ball to self-accelerating particle beams
Abstract: You might try your hand at an exactly solvable problem of nonrelativistic quantum mechanics: a hard elastic ball bouncing on a flat reflecting surface in the presence of a uniform gravitational field. That has been the subject of a series of remarkable recent experiments of ultracold neutrons bouncing along a floor in Earth’s gravity. The Schrödinger equation for stationary states of that system can be solved in terms of Airy functions, 𝐴_𝑖 (x), which were first introduced by George Biddell Airy in his study of the rainbow. Those functions are solutions of the differential equation 𝑑^2 𝐴_𝑖 (x)\/𝑑𝑥^2 = 𝑥 𝐴_𝑖 (x), which arises in the description of numerous physical phenomena. A delightful American Journal of Physics paper by Michael V. Berry and Nándor Balázs showed that Airy functions provide non trivial exact solutions of the time dependent Schrödinger equation for a free particle. Those solutions exhibit self acceleration and healing. Such solutions promoted interest in laboratory realization, which has been attained in light, electrons, and most recently by our neutron physics collaboration. I discuss the background and possible applications of this work
Host: Xiaoxing Xi
Monday, November 24, 2025 - Thanksgiving Break
Monday, November 17, 2025
Speaker: Weida Wu (Physics Department, Rutgers University)
Title: Imaging the Invisible: Domain Walls and Surface Transitions in Topological Antiferromagnets
Abstract: Once regarded as “interesting but useless,” antiferromagnets have recently emerged as fertile ground for discovering novel phenomena with potential technological applications. In particular, layered antiferromagnets with non-trivial band topology offer a promising platform for realizing exotic phenomena such as the quantum anomalous Hall effect and the axion insulator states. A major hurdle in this field has been the ability to see what’s happening inside these materials, especially the magnetic domains and domain walls that play a central role in their behavior. However, imaging antiferromagnetic domains, especially under magnetic fields, has remained a grand challenge for decades due to the absence of net magnetization. In this talk, I will share our recent progress in visualizing domain walls in the MnBi₂Te₄ and related topological antiferromagnets using cryogenic magnetic force microscopy (MFM). Our results reveal enhanced magnetic susceptibility inside the domain walls because of the winding of the antiferromagnetic order parameter. In addition, our MFM data demonstrate that the A-type antiferromagnetic order persists to the surface of both MnBi2Te4 and MnBi4Te7. This robust Atype order is further corroborated by the observation of the long-sought surface metamagnetic transitions. These discoveries not only deepen our understanding of magnetism in complex materials but also open new directions for manipulating magnetic textures in topological systems.
Host: Xifan Wu
Monday, November 10, 2025
Speaker: Jie Deng (Department of Geosciences, Princeton University)
Title: Physics of Water Inside Planets: From Earth to Exoplanets
Abstract: Water profoundly influences the evolution and habitability of planets, yet its physical behavior under extreme pressure and temperature remains poorly constrained. In this talk, I will explore the physics of water in deep planetary interiors, where it exists not as a liquid but as a dissolved, supercritical, or metallic species. Using large-scale molecular dynamics simulations driven by machine-learning interatomic potentials of ab initio quality, we quantify water solubility in the dominant silicate phase of Earth’s mantle, MgSiO3 bridgmanite, at lower-mantle conditions. The hydrogen trajectories reveal unexpectedly high solubility, suggesting that the Earth’s interior may store several ocean masses of water. Extending these insights to more massive rocky exoplanets, I will show how increasing pressure leads to partial miscibility between molten silicates and metallic iron, enabling substantial water partitioning into planetary cores. This emerging picture derived from first principles and large-scale atomistic simulations reveal how atomic scale interaction governs the deep volatile cycles of planets from Earth to super-Earths.
Host: Xifan Wu
Monday, November 3, 2025
Speaker: Chaoxing Liu (Physics Department, The Pennsylvania State University)
Title: From Atomic Crystals to Moiré Superlattices: Topology and Symmetry in Quantum Materials
Abstract: Electronic band theory, developed nearly a century ago, stands as one of the most enduring successes of quantum mechanics in explaining the electronic properties of solids. Yet, the topological nature of electronic bands has only come into focus over the past two decades, opening new directions in the study of quantum materials. This talk will explore the development of topological band theory, from its conceptual origins to its modern applications in the discovery of novel quantum materials in both atomic crystals and moiré superlattices. I will begin by introducing the concept of band inversion, a key idea that incorporated topology into band theory and guided the early search for topological materials. Subsequently, I will bridge this early concept to more sophisticated theoretical frameworks, such as topological quantum chemistry and symmetry indicators, which, when combined with first-principles calculations, enable the systematic, high-throughput screening of topological materials from large-scale material databases. Finally, I will demonstrate how moiré superlattices have emerged as a tunable platform for engineering topological flat bands, which are predicted to host a rich variety of strongly correlated topological phases.
Host: Xiaoxing Xi
Monday, October 27, 2025
Speaker: Pedro Rivero Ramírez (IBM T.J. Watson Research Center)
Title: Quantum Algorithms: From Utility to Advantage and Beyond
Abstract: In this talk, I will provide insights beyond typical algorithms that one can find in the literature to showcase how algorithm development plays a vital role in the field today, opposite to the belief that hardware is the only important thing at this point. Additionally, I will highlight IBM’s quantum roadmap and share our long-term vision for the decade ahead.
Host: Maria Iavarone
Monday, October 20, 2025 - Canceled
Monday, October 13, 2025
Speaker: Luigi Frunzio (Department of Applied Physics, Yale University)
Title: The Race to Build “Impossible” Computers
Abstract: We are celebrating the Centennial Year of Quantum Mechanics, but only now we are getting close to harness the true content of this complex world view.I will introduce the idea of a 2nd Quantum Revolution and the first main result it could carry the Quantum Computer.
Host: Maria Iavarone
Monday, October 6, 2025
Speaker: Steven M. Anlage (Physics Department, University of Maryland)
Title: Using Complex Time to Understand Complex Systems
Abstract: Time is a ubiquitous and relentless quantity that is very difficult to clearly define. However, most everyone agrees that time is a real measurable number, and its evolution is as regular as clockwork, so to speak. However, under some circumstances it may be useful to think of the interval between two events as being a complex number. Such circumstances occur, for example, when describing the propagation of pulses of light through a lossy scattering system. This story takes us into the world of “non-Hermitian physics” to explore how real-life lossy and complex systems, which are usually left for engineers to deal with, can now be understood using a set of simple physical principles. The time that it takes a pulse of light to propagate through such a system is best described using a complex quantity, which we call “complex time delay.” We prove the utility of this concept with experiments on complex interconnected one-dimensional networks of coaxial cables, known as quantum graphs. Complex time delay opens the door to deep insights into the physics of non-Hermitian systems, which we will explore briefly using more experimental results on microwave propagation through irregular structures in the high-frequency limit
Host: Xiaoxing Xi
Monday, September 29, 2025
Speaker: Arjun Yodh (Physics Department, University of Pennsylvania)
Title: Phase- and Shape-Transitions, Frustration, and Relaxation in Colloids & Liquid Crystals
Abstract: After a brief introduction to soft condensed matter physics, I willdescribe work from my lab with colloids and liquid crystals. The colloidexperiments explore novel phases, phase transition mechanisms, and relaxation in crystal films and glasses that are relevant to a broad range of hard and softmaterials. In a different vein, experiments with liquid crystal drops revealremarkable “almost biological” shape transformation behaviors.
Host: Jim Napolitano
Monday, September 22, 2025
Speaker: Yu Liu (Department of Chemistry and Biochemistry, University of Maryland College Park)
Title: Ultracold Molecules: What they are good for and how to make them
Abstract: Recent advances in AMO physics now enable precise control of simple gas-phase molecules—both in their motion and internal quantum states—opening new opportunities across multiple fields. I will highlight applications of these “ultracold molecules” in quantum information science, fundamental physics,
chemical reaction dynamics, and precision spectroscopy. The second half of my talk will focus on the production of ultracold molecules. I will discuss recent theoretical work from my group on identifying pathways to coherently assemble ultracold Li₂ molecules from ultracold Li atoms, and how this effort directly benefits from the high-quality spectroscopy data available in the literature for alkali dimers. I will also introduce a complementary approach currently under development in our lab: near-threshold photodissociation of ion–neutral complexes, a technique that could substantially expand the accessible chemical space for ultracold molecular species.
Host: Marjatta Lyyra
Monday, September 15, 2025 - Student Reports
Monday, September 8, 2025
Speaker: Paul Cadden-Zimansky (Bard College)
Title: Visualizing Quantum States
Abstract: One of the principal challenges of learning and understanding quantum mechanics is the relative lack of meaningful and useful visual images to accompany the subject's abstract mathematical formalism. In one extreme example, the Nobel Laureate Steven Weinberg composed an entire quantum textbook that contains no pictures, diagrams, plots, or graphs at all. In contrast, starting from a very young age we have many years of experience visualizing what it means for a classical object to be moving along in a location in space it's classical "state" – which provide us with helpful intuitions when we first encounter the mathematical formalisms of introductory physics. To improve our corresponding quantum intuitions, this talk will present a series of geometric maps of quantum states that can be used to introduce quantum concepts, accompany the learning of the quantum formalism, and deepen one’s understanding of its algorithms. Particular emphasis will be placed on visualizing mixed quantum states, which, despite their centrality to describing the world quantum mechanically, are often absent from quantum courses due to their more involved algebraic formalism
Host: Jim Napolitano
Monday, September 1, 2025 - Labor Day
Monday, August 25, 2025
Speaker: Johannes Hecker Denschlag (Institute für Quantenmaterie Universität Ulm, Germany)
Title: Demonstrating beam splitters for reaction pathway in the field of cold chemistry
Abstract: Our group studies chemical reactions of ultracold Rb atoms in a state-to-state resolved fashion, where we prepare reactants in well-defined quantum states and measure the quantum states of the molecular products. In particular, we focus on three-body recombination where three atoms collide, forming a diatomic molecule. The third atom carries away part of the binding energy. We are currently investigating methods to gain control over this chemical reaction. By making use of either a magnetically tunable Feshbach resonance or an avoided crossing of molecular levels we can effectively construct different kinds of beam splitters for the reaction pathways. The idea is to resonantly admix at specific points of the reaction coordinate additional quantum states to the original collision complex. This ⅔opens up an additional pathway that the reaction can take. By tuning the magnetic field in our experiments, we can control these beam splitters and can redirect a sizeable fraction of the reaction flux between different product channels. These beam splitters are fully coherent and, in the future, it should be possible to use them also in interferometric schemes for controlling the reaction.
Host: Marjatta Lyyra