Title：Moiré excitons in van der Waals Materials

Speaker: Professor Gang Lu

Time: 15:30, May 19（Monday）

Location: Room 215, No. 8 Hainayuan Building

Abstract:

Understanding excited state phenomena is at the heart of many important materials problems, such as photovoltaics, photocatalysis, plsamonics and quantum information. In this talk，I will highlight our recent progress in developing accurate and efficient first-principles methods that enable us to probe electronic excitations in emerging materials. In particular, I' II focus on a linear-response time-dependent density functional theory (LR-TDDFT) methond with optimally tuned, screened and range-separated hybrid (OT-SRSH) exchange-correlation functional that can compute exciton band structure, exciton charge density, excited state forces, and exciton-phonon coupling matrix accurately for large-scale extended systems. Fourmulated with spinor wavefunctions, the LR-TDDFT method enables calculations of noncollinear magnetism and spin-orbit coupling and can be combined with non-adiabatic molecular dynamics to explore exciton dynamics. Using this method, we have examined electron excitations in 2D van der Waals materials, including moiré excitons, moiré magnetism, exciton dynamics, and Bose-Einstein condensation of moiré excitons.

Biography:

Prof. Lu received his PhD from Chinese Academy of Sciences while most of his PhD work was carried out in his current institution-California State University Northridge (CSUN). After a postdoc appointment at Harvard, Prof. Lu returned to CSUN as a faculty member is 2004 and was promoted to a full professor in 2009. He is the director of NSF-funded PREM center on Quantum Materials and the founding director of the Center of Excellence in Materials Innovation, both at CSUN. Prof. Lu spends significant research effort in developing first-principles based multiscale computational methods and has applied these methods to various materials problems. Some of the prblems relevant to electronic excitations in 2D materials (e.g., moiré  excitons) will be highlighted in the talk.