Research Overview

We work at the intersection of materials and physics
It is an exciting time to study the physics of materials. From novel semiconductors and oxides for electronics, to ultrathin materials for optical and energy devices to quantum materials for emerging quantum technologies, materials are becoming increasingly complex materials. Empirical models developed decades ago, and 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 the material, and aim to make quantitative predictions without using any tuning parameters or input from experiments. These methods can make predictions with quantitative accuracy and provide an unprecedented microscopic insight into the behavior of materials. This enables 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 aspects of this problem, focusing on understanding the interactions and motions
of electrons, atoms, and other excitations in materials:

  1. Electronic interactions: We devevelop 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 in 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.

  2. Transport: We study electronic transport in novel semiconductors, oxides, and 2D materials to advancing microscopic understanding of transport phenomena and novel transport regimes. We have shown accurate predictions of transport in inorganic and organic semiconductors; explained the origin of the electron mobility in complex oxides; developed accurate calculations of electronic transport in strongly correlated materials, unraveling the electronic and lattice contributions to the resistivity; and advanced modeling of transport in magnetic and electric fields from low to high temperatures. These studies have greatly expanded the depth and scope of first-principles quantum mechanical calculations of transport phenomena in materials.

  3. Spin physics: A microscopic understanding of electron spin dynamics is essential to advancing quantum technologies. We havee developed theory and computational methods that can precisely characterize electron spin relaxation and decoherence, focusing on the role of phonons (atomic vibrations), which set an intrinsic limit to 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.

  4. Nonequilibrium dynamics: We study materials excited out of equilibrium to characterize the resulting ultrafast dynamics and the associated time-domain spectroscopies. We have developed new first-principles techniques to study excited electron and lattice dynamics in materials, and expanded these approaches in multiple ways to study a wide range of nonequilibrium physics in materials and simulate ultrafast spectroscopies. This work has led to predictions of novel ultrafast electronic behaviors as well as predictions of light-emission and radiative processes in a range of crystals and 2D materials. These studies generate new tools to understand excited materials and their nonequilibrium physics.

  5. Software development: We work on open source software to share our novel tools and computational workflows with the community. We have developed and released PERTURBO, an open source code with hundreds of users that enables quantitative studies of electron interactions and dynamics in materials. PERTURBO equips the scientific community with cutting-edge tools and efficient algorithms to study interactions and dynamics in novel conventional and quantum materials.

Our research is highly interdisciplinary
Our studies span multiple disciplines, including physics, materials science, engineering, and physical chemistry. By breaking new grounds in materials physics, we seek to push scientific frontiers with broad societal impact. Current and future work focus on using computers to understand interactions in matter with ultimate microscopic resolution, advancing next-generation quantum materials and devices, and exploring the machine learning/AI frontier to understand quantum matter.


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