Research

Research directions

It is an exciting time to study the physics of materials. From novel semiconductors and oxides for electronics, to ultrathin materials for optical devices, to quantum materials and emerging quantum technologies, materials are becoming increasingly complex. Empirical models developed decades ago, though still widely used, are inadequate to understand these emerging conventional and quantum materials and their novel physics.

With this motivation, our research develops numerical quantum-mechanical calculations to understand the interactions and motion of electrons, atoms, and various excitations in materials. We focus on first-principles approaches, which take as input only the atomic positions inside a material and aim to make quantitative predictions without tuning parameters or experimental input. These methods achieve quantitative accuracy while providing unprecedented microscopic insight into material behavior, enabling the interpretation of cutting-edge experiments on new classes of materials and the design of materials with novel combinations of properties. Our research spans several interconnected areas, centered on understanding the interactions and motion of electrons, atoms, and other excitations in materials:

Electronic interactions. We develop accurate calculations of electronic interactions in materials, including the interactions between electrons and atomic vibrations (phonons). These electron-phonon (e-ph) interactions govern wide-ranging phenomena in solids, including transport, nonequilibrium dynamics, superconductivity, and phase transitions. Our work has pioneered precise calculations of e-ph interactions across a wide range of materials of fundamental and technological interest, including materials with polar or ionic bonds, piezoelectricity, spin-orbit coupling, strong e-ph interactions and polarons, electron-hole interactions and excitons, and strong electronic correlations.
Transport. We study electronic transport in novel semiconductors, oxides, and 2D materials to advance the microscopic understanding of transport phenomena and novel transport regimes. We have demonstrated accurate predictions of transport in inorganic and organic semiconductors; explained the origin of electron mobility in complex oxides; unraveled the electronic and lattice contributions to resistivity in strongly correlated materials; and advanced the modeling of transport in electric/magnetic fields and in the presence of nontrivial band topology. These studies have significantly expanded the depth and scope of first-principles calculations of transport phenomena in materials.
Spin physics. A microscopic understanding of electron spin dynamics is essential to advancing quantum technologies. We have developed theory and computational methods that precisely characterize electron spin relaxation and decoherence, with a focus on the role of phonons, which set an intrinsic limit on the performance of spin-based quantum devices. We have demonstrated accurate predictions of spin relaxation and derived a unified approach to describe phonon-induced spin dynamics. We are building on these advances to study spin dynamics in quantum materials and devices.
Nonequilibrium dynamics. We study materials excited out of equilibrium to characterize the resulting ultrafast dynamics and associated time-domain spectroscopies. We have developed new first-principles techniques to study excited electron and driven lattice dynamics, and have extended these approaches in multiple directions to capture a wide range of nonequilibrium physics. This work has led to predictions of novel ultrafast electronic behaviors and interpretation of ultrafast spectra in a range of bulk and 2D crystals, generating new tools to understand excited materials and their nonequilibrium physics.
Software development. We develop open-source software to share our tools and computational workflows with the community. We created and maintain PERTURBO, an open-source code with hundreds of users worldwide that enables quantitative studies of electron interactions and dynamics in materials. PERTURBO equips the scientific community with cutting-edge tools and efficient algorithms for studying interactions and dynamics in conventional and quantum materials.

An interdisciplinary approach
Our work spans physics, materials science, engineering, physical chemistry, and quantum science. By pushing the frontiers of materials physics, we aim to advance fundamental science with broad societal impact. Current and future directions include developing accurate methods to understand interactions in materials, advancing next-generation quantum materials and devices, and leveraging machine learning/AI to both accelerate calculations of quantum interactions and compute previously intractable interactions.

See the Publications and News sections for more on our work.