Condensed Matter Seminar

Abstract: The driven-dissipative many-body systems remain one of the most challenging unsolved problems of quantum physics. When “body” is spin, such as of electrons or of engineered ones like qubits, these many-body systems underlie spintronics, magnonics and quantum computing technologies. In this talk, I first explain conditions [1] under which quantum spins interacting with a dissipative environment can transition toward classical dynamics governed by the celebrated Landau-Lifshitz-Gilbert (LLG) equation.

Abstract: In frustrated magnetic systems with a subextensive number of classical ground states, quantum zero-point fluctuations can select a unique long-range ordered state, a celebrated phenomenon referred to as order by quantum disorder (ObQD). For frustrated spin-1/2 models, unbiased numerical methods able to expose ObQD are necessary. We show that ObQD can be identified from exact diagonalization calculations through an analysis akin to the Anderson tower of states associated with spontaneous symmetry breaking.

Abstract: Geometrically frustrated antiferromagnets are leading candidates for realizing quantum spin liquid (QSL) states. While there is a consensus on the existence of a QSL phase, its precise nature remains largely under debate. In this talk, I will argue that the situation is more intricate: multiple competing states can arise in the QSL-relevant regime with distinct dynamical spectral signatures. This behavior is robust across different cluster sizes, suggesting the persistence of these competing states towards the thermodynamic limit.

Abstract: In a flat band system, the charge carriers’ energy-momentum relation is very weakly dispersive. The resultant large density of states and the dominance of Coulomb potential energy relative to the kinetic energy favor the formation of strongly correlated electron states, such as ferromagnetism, nematicity, and superconductivity. The advent of two-dimensional (2D) materials and their heterostructures has ushered in a new era for exploring, tuning and engineering of flat band system.

Abstract: Hydrogen adsorption and absorption in metals and oxides are relevant to a wide range of energy- and environment-related applications, including hydrogen storage, high-temperature superconductivity, and catalytic processes. Because hydrogen is the lightest atom and possesses spins, it is often argued that quantum effects play an important role in its dynamics.

Abstract: “Floquet engineering” - the design of band structures on demand through coherent time periodic drives, has emerged as a powerful route to inducing exotic phenomena in otherwise conventional materials. In this talk, I will discuss how Floquet engineering can be used to generate novel non-equilibrium phases of matter in the steady states of driven semiconductors. These steady states arise from the interplay between coherent driving, electron-electron interactions, and dissipation due to coupling to phonons and the electromagnetic environment.

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.