时间: 2024年12月5日（星期四）下午14:00-15:30

Time:14:00-15:30, Thursday, December 5, 2024

主持人: 西湖大学物理系PI 刘仕

Host:Dr. Shi Liu, PI of School of Science, Westlake University

地点: 云谷校区E10-211教室

Venue:E10-211, Yungu Campus, Westlake University

讲座语言: 中文

Lecture Language:Chinese

Prof. Sheng Meng,

Institute of Physics, Chinese Academy of Sciences, Beijing 100190, China

主讲人/Speaker:

Dr. Sheng Meng is a professor and director of Surface Science Laboratories at Institute of Physics, Chinese Academy of Sciences. He obtained his Bachelor degree in physics from University of Science and Technology of China (USTC) in 2000, and Ph.D. degree in condensed matter physics from Institute of Physics, Chinese Academy of Sciences and applied physics from Chalmers University of Technology, Sweden in 2004. During 2005-2009, he worked at Harvard University’s Department of Physics first as a post-doctoral researcher then a research associate. Dr. Meng’s research interests focus on excited state quantum dynamics of condensed matter; design of quantum materials; energy conversion mechanism for sustainable society; as well as new algorithms and tools in materials computation. He has published ~200 technical papers in peer-reviewed journals, and has received 18000+ citations. Dr. Meng receives various awards including first-tier prize in science and technology of Beijing municipality, NSFC outstanding youth investigator awards etc. He is an elected fellow of American Physics Society (APS).

讲座摘要/Abstract:

Photoexcitation is a powerful means in distinguishing different interactions and manipulating the states of matter, especially in complex quantum materials. Here we illustrate photoexcitation-induced ultrafast dynamics in two-dimensional materials, as well as the development of new theoretical tools incorporating both nonadiabatic electron-nuclear couplings and nuclear quantum effects for atomic scale simulations of such ultrafast processes. For instance, we discover a collective pathway from 2H phase to 1T phase in MoTe2 induced by photoexcitation, which is significantly different from thermal phase transitions. We also find a novel quantum phase inversion mechanism in the charge density wave (CDW) state of TiSe2, which involves self-amplified exciton-phonon dynamics for the formation of charge density waves. We will also discuss photoinduced electronic phases, structural changes and the coupled exciton-lattice orders, such as controlling the dynamics of intervalley exciton transport and Weyl quasiparticles in two-dimensional materials. Our results provide insights from a new perspective on the coherent electron-lattice quantum dynamics in materials upon photoexcitation.

References:

1. P.W. You, D.Q. Chen, X.B. Liu, C. Zhang, A. Selloni, S. Meng. Correlated electron-nuclear dynamics of photoinduced water dissociation on rutile TiO2. Nature Materials 23, 1100 (2024).

2. R.J. Zhao, P.W. You, S. Meng, Ring polymer molecular dynamics with electronic transitions, Phys. Rev. Lett. 130, 166401 (2023).

3. C.Y. Wang, X.B. Liu, Q. Chen, D.Q. Chen, Y.X. Wang, S. Meng. Coherent-Phonon-Driven Intervalley Scattering and Rabi Oscillation in Multivalley 2D Materials. Phys. Rev. Lett. 131, 066401 (2023).

4. Z.W. Nie, Y.X. Wang, D.Q. Chen, S. Meng. Unraveling hidden charge density wave phases in 1T-TiSe2. Phys. Rev. Lett. 131, 196401 (2023).

5. M.X. Guan, D.Q. Chen, Q. Chen, Y.G. Yao, S. Meng. Coherent Phonon Assisted Ultrafast Order-Parameter Reversal and Hidden Metallic State in Ta2NiSe. Phys. Rev. Lett. 131, 256503 (2023).

6. M.X. Guan, X.B. Liu, D.Q. Chen, X.Y. Li, Y.P. Qi, Q. Yang, P.W. You, S. Meng. Optical control of multi-stage phase transition via phonon couplings in MoTe2. Phys. Rev. Lett. 128, 015702 (2022).

7. J.Y. Xu, D.Q. Chen, S. Meng. Decoupled ultrafast electronic and structural phase transitions in photoexcited monoclinic VO2. Science Advances 8, eadd2392 (2022).