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*CANCELLED due to illness* TYC Highlight Seminar: Photophysics of two-dimensional materials and moiré structures

27 September @ 4:00 pm 5:00 pm

Venue: G20 in the Royal School of Mines (Dept of Materials), Imperial College London

Steven G. Louie – University of California at Berkeley, and Lawrence Berkeley National Lab

Abstract: Enhanced many-electron interactions, strong spatial/environmental-dependent screening, as well as distinct topology in reduced-dimensional systems often lead to novel phenomena of fundamental and technological interests. In this talk, I present some recent progress along this direction in the photophysics of some systems of current interest, including atomically thin two-dimensional (2D) materials and their moiré structures. Different measurements and phenomena entail different levels of conceptual/theoretical treatments. Their understanding and prediction are a challenging quantum many-body problem. We address this problem employing an ab initio interacting n-particle Green’s function approach.

Some fascinating phenomena discovered in recent studies are presented – e.g., strongly bound excitons (electron-hole pairs) with highly unusual level structures and optical selection rules; unique moiré excitons in van der Waals heterostructures; tunable magneto-optical & plasmonic properties; prominent correlated 3- and 4-particle excitations; exciton enhanced nonlinear optical responses; remarkable field-driven nonequilibrium and time-dependent effects in pump-probe measurements, etc. Our latest ab initio field-driven studies lead to the discovery of a self-driven exciton-Floquet effect as well as the discovery of a strikingly new phenomenon of formation of light-induced shift current vortex crystals in van der Waals moiré systems. The richness of the photophysics of these materials add to their promise for exploration of new science and valuable applications.

Bio: Steven G. Louie received his Ph.D. in physics from the University of California at Berkeley in 1976.  After having worked at the IBM Watson Research Center, Bell Labs, and U of Penn, he joined the UC Berkeley faculty in 1980, where he is Distinguished Professor of Physics and a Senior Faculty Scientist at the Lawrence Berkeley National Lab.  He is an elected member of the National Academy of Sciences, the American Academy of Arts & Sciences, the Academia Sinica (Taiwan), and a foreign member of the Chinese Academy of Sciences, as well as a fellow of the American Physical Society (APS), the American Association for the Advancement of Science, and the Materials Research Society (MRS).

He is a recipient of the APS Aneesur Rahman Prize, the APS Davisson-Germer Prize, the MRS Materials Theory Award, the Foresight Institute Richard Feynman Prize, the DoE Award for Sustained Outstanding Research in Solid State Physics, as well as named Jubilee Professor of Chalmers University of Technology, Ørsted Lecturer of Technical University of Denmark, and Benjamin Lee Professor Award of the Asia Pacific Center for Theoretical Physics, among others.  Louie’s research spans a broad spectrum of topics in condensed matter physics and nanoscience.  He is known for his pioneering development of the ab initio GW method and for his studies of novel bulk and reduced-dimensional systems.

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