Physics and Astronomy

Abstract: Phase transitions, metastability, and hysteresis in porous materials remain some of the most elusive phenomena in adsorption science — difficult to predict, and even harder to control. Yet controlling them is essential: hysteresis limits the efficiency of carbon capture, water harvesting, and adsorption-based cooling cycles. In this talk, I present a molecular-level framework for understanding and designing adsorption processes. Using Transition Matrix Monte Carlo (TMMC), we directly access free energy landscapes and characterize adsorption mechanisms beyond conventional isotherms, providing a broader picture that reveals the molecular origins of hysteresis and quantifies the associated free energy barriers. Building on this understanding, 

I show how we can move from analysis to design. Using a GPU-accelerated implementation combined with optimization techniques, we systematically tune host–guest interactions to control adsorption behavior. We demonstrate how modifying the distribution of interaction sites alters nucleation pathways and enables direct control over hysteresis: its width, shape, and ultimately its mitigation. Finally, I show how these concepts translate to realistic materials, such as metal–organic frameworks (MOFs), with applications in water harvesting, carbon capture under humid conditions, and adsorption cooling. Together, this work demonstrates how molecular simulations can not only explain adsorption phenomena but guide the design of next-generation functional materials.

Abstract: Recent advances in laser technology allow for higher levels of quantum state control in materials. After a survey of recent experimental results, I will describe recent theoretical studies from my group exploring different mechanisms of quantum state control.  I will discuss situations of coexisting competing orders, Floquet engineering of pseudo-magnetic fields, and a scheme for opto-electrical control of chiral lattice structure for reversible, non-contact enantiomer control in a material.  The signatures of these states and transitions in various observables will be discussed.  I will conclude with an outlook on the field and important open questions.

Abstract:
We know from everyday life that a collection of atoms organizes itself into a solid, liquid, or gas, depending on the external conditions. But how do many interacting electrons organize themselves, and collectively evolve with time? This question has traditionally been formidable for systems where the correlations between electrons are strong - which is the case for quantum systems with "frustration". These systems are abundant in nature and can also be artificially engineered. While theory has predicted “Wigner crystals,” "valence bond solids", and “quantum spin liquids” to exist, only recently has progress been made in realizing them in the lab. Motivated by these advances, I will discuss our theoretical and numerical work, hunting for these phases in real materials -- this includes highly frustrated pyrochlore and triangular moire systems. The second part of the talk, inspired by questions that arise from the first one, is based on our contributions to the exciting developments in the study of nonequilibrium dynamics of quantum magnetic systems. I will highlight our proposal for a simple model of frustration that offers a way to understand glassiness (in the absence of disorder), a variant of which has been recently realized and studied experimentally in an artificial atom setup. I conclude by discussing avenues for future research on equilibrium and nonequilibrium dynamical phenomena.

Speaker bio:
Hitesh Changlani is an Associate Professor at Florida State University and also associated with the national High Magnetic Field Laboratory (MagLab). Prof. Changlani received his B.Tech. in Engineering Physics from IIT Bombay in 2007, and his Ph.D. in Physics from Cornell University in 2013. Following postdoctoral positions at the Institute for Condensed Matter Theory, University of Illinois at Urbana-Champaign and the Institute for Quantum Matter, Johns Hopkins University, he joined the FSU faculty in 2018. His research in theoretical and computational condensed matter physics focuses on quantum systems with many strongly interacting particles. He is the recipient of an NSF CAREER award.

Abstract: In recent years, bilayers and moire superlattices of van der Waals materials have surfaced as new tunable quantum platforms for the realization of emergent phases. While moire-induced electronic phases have been extensively explored over the past few years, moire engineering of magnetic phases is a newer emerging topic. In the first part of my talk, I will discuss how stacking dependent interlayer exchange can be used to create novel spin textures such as skyrmions. I will illustrate this mechanism by applying it to twisted bilayers of Cr-based trihalides and α-RuCl3. In addition, I will discuss competition of magnetic order and heavy fermion formation in artificial Kondo superlattices. In the second part, I will focus on quantum spin liquid bilayers and discuss how twist angle and interlayer exchange can be utilized to create new topological phases with emergent quasiparticles such as ‘fractionalized Goldstone modes’ in these systems.

Short bio: Onur Erten received his Ph.D. from The Ohio State University. He held postdoctoral positions at Rutgers University and the Max Planck Institute for the Physics of Complex Systems before joining Arizona State University, where he is currently an associate professor. His research focuses on theoreti[1]cal condensed matter physics, with interests spanning strongly correlated elec[1]tron systems, quantum magnetism, superconductivity, and topological phases in quantum materials.

Abstract: In this talk, I will provide a brief overview of the recent Nobel Prize in Physics awarded to John Clarke, Michel H. Devoret, and John M. Martinis for the discovery of macroscopic quantum mechanical tunneling and energy quantization in an electric circuit. Alongside a historical background, I will highlight the key ideas behind their contributions and conclude with a discussion of current open challenges and frontiers in the field.

Non-Equilibrium and Entropy-Driven Transport Physics in Multicomponent Materials under Extreme Conditions 

Chaochao Dun (Lawrence Berkeley National Laboratory)

Abstract: Functional stability under extreme thermal, chemical, mechanical, and irradiation environments remains a central challenge for modern energy and aerospace systems. Conventional equilibrium-based materials design limits accessible compositions and microstructures. From an applied physics perspective, the key question becomes: how do non-equilibrium processes and entropy govern phase stability, defect formation, and transport under extreme conditions?

In this talk, I present a framework that treats non-equilibrium pathways and entropy as physically controllable variables. Using flame–aerosol synthesis as a well-defined experimental approach, I access multicomponent materials beyond equilibrium phase limits and systematically examine how kinetic constraints and entropy influence phase retention and defect-mediated transport. Representative case studies span binary solid solutions, high-entropy ceramics, and high-entropy alloys, illustrating how kinetic control and entropy stabilization regulate defect landscapes, suppress phase separation, and improve functional performance in catalysis and energy conversion. I will also discuss related examples in flexible biosensing platforms, where disorder–transport coupling governs mechanical compliance and signal stability.

Finally, I describe how this research program can be developed at the University of Missouri by integrating high-throughput non-equilibrium synthesis, quantitative structure–property characterization through the Electron Microscopy Core (EMC), and neutron irradiation at MURR. Together, these capabilities enable systematic investigation of how multicomponentstructure governs transport and stability under coupled extreme conditions.

Light across space and phase: creating spin-photon interfaces and probing single-photon emitters

Feng Pan

Department of Materials Science and Engineering, Stanford University

Abstract:

In quantum technologies, room-temperature photonic devices—such as quantum transducers and single-photon light sources—are key building blocks for scalable quantum networks and energy-efficient quantum computing. Yet today’s devices are often limited by rapid decoherence at room temperature, low conversion or emission efficiency, and material-to-material variability that makes performance hard to reproduce. By sculpting light–matter interactions with nanophotonic structures and probing emitters with quantum-optics–based spectroscopy, we can create new routes to robust, high-performance quantum devices.

In this talk, I will present three stories across three material platforms that illustrate this approach, unified by room-temperature operation. First, I will show how engineered symmetry in silicon chiroptical cavities couples the spin of light to electron spin in two-dimensional molybdenum diselenide (MoSe2) monolayers within a Si–MoSe2 heterostructure, enabling efficient room-temperature spin–photon interfaces and a pathway toward scalable hybrid quantum architectures. Second, I will demonstrate how symmetry-controlled nanostructuring of subwavelength-thick nonlinear AlGaAs thin films generates spin-encoded entangled photon pairs at room temperature with efficiencies comparable to those of conventional bulk crystals. Third, I will describe how photon-correlation measurements can disentangle distinct dynamical processes—spanning nanoseconds to milliseconds—in two-dimensional hexagonal boron nitride single-photon emitters that operate at room temperature. Together, these studies highlight how nanophotonic engineering and quantum-optics characterization can accelerate the development of practical room-temperature photonic quantum devices.

Abstract: Biological systems function through intricate yet well-balanced biomolecular processes. Probing critical bioanalytes, such as protein biomarkers, therapeutic drugs, and metabolites, provides a powerful lens into human health and bioprocess performance, as even trace amounts of emerging biomarkers or subtle variations in process parameters can signal pathological changes or system malfunctions. However, achieving high measurement accuracy and precision remains challenging due to limitations in sensitivity, specificity, and robustness of existing bioanalytical techniques.

Surface-enhanced Raman spectroscopy (SERS) offers exquisite molecular specificity, single-molecule sensitivity, and high spatial resolution, making it a compelling candidate for translational biophotonic diagnostics. Yet, its adoption as a quantitative measurement tool is hindered by the SERS uncertainty principle and substantial intensity fluctuations arising from heterogeneous SERS hotspot distribution, non-uniform analyte deposition, a short field decay length, and dynamic analyte-metal interactions.

To address these challenges, in this talk, I will present three complementary and progressively sophisticated spectroscopic platforms to advance translational biophotonic diagnostics by leveraging plasmonic and quantum polaritonic principles.

First, I will introduce a SERS frequency shift-based single-antibody immunoassay, which decouples measurement signals from intensity fluctuations by transducing molecular recognition into SERS frequency shifts. Its clinical relevance has been validated under stringent industrial detection protocols provided by Beckman Coulter Diagnostics through robust detection of thyroid-stimulating hormones in patient samples, ultrasensitive detection of an acute myocardial infarction biomarker panel, and high-precision spectrally super-resolved colloidal SERS detection of a protein biomarker panel spanning endocrine, cardiovascular, and hemostatic disorders.

Second, I will present a label-free digital SERS assay, which converts fluctuating spectra into binary “ON/OFF” signals, thereby mitigating intensity variations and minimizing false positives. Integration with deep learning substantially broadens analyte coverage and enables precise, rapid, and ultrasensitive monitoring of chemically defined AMBIC cell culture media and urine neurotransmitters. Its industrial translational potential has been validated through projects supported by AMBIC, Cohen Translational Engineering Fund, and Maryland Innovation Initiative Technology Assessment Grant, with endorsements from Boehringer Ingelheim, Genentech, AstraZeneca, and NIST.

Third, I will introduce quantum polaritonic biosensing, which provides a fundamentally new strategy to interrogate molecules by dressing molecular states with cavity photons under ambient conditions. The resulting Rabi doublet peak splitting marks a substantial enhancement in sensitivity and specificity when compared to classical sensing, and provides quantum vibro-polaritonic fingerprints of molecules, paving the way for quantum vibro-polaritonic spectroscopy for accurate molecular profiling of therapeutic drugs.

Together, these advances establish new pathways for practical biophotonic diagnostics by integrating nanoengineering, artificial intelligence, plasmonics, and quantum optics.

N/B: Please note that this event is not being held on our usual colloquium day, which is Monday.

Abstract: Functional polymers provide a versatile platform for engineering materials in which ionic, 
electronic, and mass transport can be tuned through controlled nanostructure. Yet achieving 
predictive performance in these systems requires understanding how phase behavior, nonequilibrium assembly, and solid-liquid interactions govern structure formation across multiple 
length scales.

Morphology and phase segregation fundamentally dictate charge and ion transport in applications 
ranging from ion-selective membranes to bioelectronic devices and biosensors. In this talk, I will 
discuss how nanoscale domains, interfacial structures, and nanoconfinement govern ionic 
partitioning and electronic percolation, and how these structural parameters can be deliberately 
engineered to control transport behavior and electrochemical response. By integrating materials 
design with quantitative nanoscale analysis enabled by cryogenic electron microscopy, we 
establish structure-transport relationships that support the predictive tuning of polymer blends for 
targeted applications.

Abstract: Key functional phenomena - from vision and photosynthesis to advanced optoelectronics and photonics - originate from ultrafast microscopic photophysical dynamics. Macroscopic properties emerge from electronic and structural evolution, often occurring on ultrafast time scales of femtoseconds. Ultrafast spectroscopy allows us to directly resolve these processes.

My research establishes optical pump–probe microscopy as a powerful, highly sensitive ultrafast imaging platform. I will discuss our latest advances in ultrafast pump-probe microscopy, which enable us to image the system in femtoseconds and to visualize the photophysical processes in complex systems with femtosecond time resolution and sub-micrometer spatial resolution. I will discuss our implementation of ultrafast time-resolved pump-probe transient absorption microscopy-spectroscopy for highly sensitive photophysical and photochemical analysis of energy conversion materials, as well as bioinspired and biocompatible optoelectronic material systems prepared in our lab.

N/B: Please note that this event is not being held on our usual colloquium day, which is Monday.