Condensed Matter Seminar

Abstract: Solid-state physics (SSP) is broad branch of condensed matter physics that studies the physical properties of rigid matter, or solids.  It employs principles from quantum mechanics, crystallography, and electromagnetism to understand how the arrangement of atoms in a solid gives rise to its macroscopic properties, such as electrical conductivity, heat capacity, and magnetic behavior. SSP and quantum materials are deeply interconnected fields, with the former providing the foundational knowledge and tools to explore the frontiers of the latter.

Abstract: I will discuss recent advances in modeling coupled electronic and vibrational dynamics that govern energy flow in condensed-phase systems. I will first present all-state quantum dynamics simulations of excitation energy transfer in the bacterial light-harvesting complex (LH2), showing how its ~90% efficiency and ~1 ps timescale arise from its concentric pigment architecture and nuclear quantum effects.

Abstract: Chirality is a ubiquitous organizing principle in nature and a powerful route to new quantum functionalities. In quantum materials, chirality can be encoded in crystal structure, induced by external magnetic fields, or emerge spontaneously through symmetry breaking. It underlies a broad class of phenomena, including magnetic skyrmions, fractional quantum Hall states and their lattice analogs (fractional Chern insulators), and chiral superconductivity.

Abstract: When two-dimensional materials are stacked with a relative twist, an emergent moiré translation symmetry reshapes their low-energy electronic structure, giving rise to qualitatively new phases of matter. In recent years, moiré materials have emerged as highly tunable platforms for exploring strong electronic correlations, enabling controlled realizations of many paradigmatic models of condensed matter physics within engineered heterostructures.

Abstract: Condensed matter physics has been driven by the discovery of novel phases of matter, such as topological materials.  Most recently, advances in the controllability of quantum simulators and computers have enabled both a vast new landscape of non-equilibrium phases of matter and fault tolerant quantum memories.  I will first show how conditional mutual information (CMI) serves as an essential quantity in characterizing these phases of open quantum systems and their transitions.  Remarkably, these insights have led to new diagnostics for both quantum error correctio

Abstract: In many problems spanning transition-metal catalysis and quantum materials, quantitative prediction hinges on treating electron correlation and electron–phonon coupling beyond standard mean-field and perturbative approaches. In this talk, I will describe our efforts to advance the auxiliary field quantum Monte Carlo (AFQMC) method, enabling first-principles electronic structure calculations in challenging correlated systems with accuracy beyond state of the art coupled cluster methods and more favorable cost scaling.

Abstract: Strong electron correlations can transform simple chemical building blocks into quantum materials with striking macroscopic signatures, such as high-Tc superconductivity and charge density waves. Yet a central challenge remains: how do we quantitatively connect atomic-scale chemical composition and crystal structure to emergent quantum behavior, without relying on empirical parameters?  In this seminar, I will describe ab initio many-body theories to uncover microscopic “design rules” for correlated quantum materials.

Abstract: Recent experiments on rhombohedral multilayer graphene (RMG) with a substrate-induced moire potential have identified both Chern insulators and fractional Quantum Hall states at zero magnetic field, whose origin is presently mysterious. The operative degrees of freedom are in the valence band minima that feature strong correlations and non-trivial quantum geometry. The first part of this talk will study a microscopic model of RMG.

Abstract: Controlling phases of matter with light is a central goal in condensed matter physics. I will present new theories of light–matter interaction that show how light shapes and drives instabilities in quantum materials across electronic, structural, and collective-mode sectors. First, I show that resonant optical absorption can drive layer sliding in van der Waals flakes (e.g. in CrI3, MoTe2, MoSe2) via nonlinear light–matter coupling.

Abstract: Semiconductor moiré lattices provide a flexible platform to study flat, topological bands that host a variety of closely competing many-body ground states. In this talk, I will present single-electron transistor microscopy of WSe2 bilayers at low twist angles, which reveals rich interplay between magnetism, correlations, and topology. At zero magnetic field, we observe a series of quantum anomalous Hall states and demonstrate topological phase transitions as a function of twist angle and electric field.