CAREER: First-Principles Electron and Spin Dynamics in Materials with Spin-Orbit Coupling

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NONTECHNICAL SUMMARYThis CAREER award supports research and education in developing computational methodology for investigating and understanding in detail the motion of electrons in materials. The focus of the research is on a property of electrons called spin, which is analogous to the spinning rotation of a planet around its axis. In materials containing heavy atoms, such as bismuth or tungsten among others, the spin and spatial motions of electrons are coupled; this so-called spin-orbit coupling is at the center of recent breakthroughs in materials physics. The objective of the research is to develop accurate methodology for the calculation of the dynamics of electrons in materials where spin-orbit coupling is significant. In contrast to conventional studies, which typically employ simple models to interpret experiments, the goal is to develop truly predictive calculations that are free of empirical parameters and can be applied broadly to new materials. By accurately computing the interactions of electrons with atomic vibrations and defects in the crystal structure of the material, the project will develop a microscopic understanding of materials with yet untapped potential for new technology, including novel metals and ultrathin semiconductors containing heavy atoms. The work will generate knowledge and computational methods needed for breakthrough advances in electronics, renewable energy, spectroscopy, computing, and quantum technology. These efforts are critical for establishing a United States leadership in emerging technologies based on novel materials. The computational methods generated in the project will be freely available, user-friendly, and widely usable; users will include academic research groups, national laboratories, and the industry. This project aims to be an enriching opportunity for the high-school, undergraduate, and graduate students involved. The PI will train high-school students on scientific computing through engaging activities. The research team will host undergraduate students, who will contribute to research and develop their curricula by learning cutting-edge computational materials physics. The project will contribute to the development of graduate students with a unique interdisciplinary background at the intersection of physics, computer science, and materials science. They will be equipped to lead computational physics and materials science research in the United States. TECHNICAL SUMMARYThis CAREER award supports research and education in developing a detailed understanding of the dynamics of charge carriers and their spin in materials with spin-orbit coupling. The project will develop new theory and computational methods to accurately calculate the timescale and mechanisms of scattering, relaxation, transport, and ultrafast dynamics of electrons and spin in materials with spin-orbit coupling. While computations of charge and spin dynamics are typically heuristic, the PI will develop predictive first-principles calculations based on density functional theory and related methods that are free of empirical parameters and can be applied broadly to new materials. By accurately computing the interactions of electrons and spin with lattice vibrations and crystallographic defects, the project will develop a microscopic understanding of materials with yet untapped potential for new technology. The research team will focus on a range of materials with spin-orbit coupling, including two-dimensional transition-metal dichalcogenides for novel optoelectronic devices, lead-halide perovskites for efficient solar cells, and topological semiconductors and semimetals for new fundamentals physics. The complex atomic structure in these materials underscores the need for accurate and broadly applicable methods to compute carrier and spin dynamics in materials. The new methods and code generated in the project will be included in PERTURBO, a software developed by the PI to advance understanding of electron and excited-state dynamics in materials. The first-principles approach pursued here can be applied broadly to electronic and spin-based devices, as well as to advancing ultrafast electron and spin spectroscopies. These efforts are critical for establishing a United States leadership in emerging electronic, renewable energy, computing, and quantum technologies. The project integrates research and education by training a new generation of high-school and undergraduate students in scientific computing. The graduate students working on the project will acquire a unique interdisciplinary background at the intersection of physics, computer science, and materials science. They will be equipped to lead computational physics and materials science research in the United States.