| 报告人简介 | Dr. Chen Hu is an Assistant Professor in the Department of Physics at the Chinese University of Hong Kong. He was a postdoctoral research fellow at the University of California, Berkeley, and the Lawrence Berkeley National Laboratory from 2021 to 2024. He earned his PhD in physics from McGill University in Canada in 2020. His research engages in the fields of theoretical condensed matter physics and computational material science, with the primary aim of exploring novel quantum material physics through advanced first-principles theoretical methodologies and computational tools. He focuses on intriguing photoexcited phenomena, ultrafast and nonlinear optoelectronics, topological physics, quantum transport and spintronics in emerging low-dimensional quantum materials and nanodevices. |
报告摘要 | Employing light to study intriguing phenomena or to induce and tune exotic phases of matter lies at the heart of condensed matter science and optoelectronic technologies. Recent developments in optical spectroscopies have provided rich experimental signatures of novel excited states and ultrafast photoexcited responses in 2D van der Waals (vdW) heterostructures; however, the nature of many of these phenomena remains to be fully explored. In this talk, I will discuss our two recent works in this direction, based on a newly-developed first-principles time-dependent interacting Green’s function approach. First, I will demonstrate a new excitonic mechanism for the photoexcited interlayer exciton dynamics (and associated ultrafast optical responses) in transition metal dichalcogenide (TMD) vdW heterobilayers [1], which is conceptually different from the conventional single-particle picture. Strong excitonic couplings are discovered to be a main driving in the ultrafast exciton and optical dynamics. Second, I will show that the excitonic physics could also greatly enhance the nonlinear optical responses in vdW moiré superlattices, leading to a striking phenomenon of formation of light-induced nonlinear photocurrent vortex crystals—i.e., 2D arrays of moiré-scale current vortices and associated magnetic fields [2]. It provides a promising all-optical control route to manipulate such exotic photoexcited moiré quantum matter. Our findings illustrate the richness in the photophysics of vdW heterostructures and open opportunities for applications in optoelectronics and photovoltaics. [1] Hu, Naik, Chan, and Louie, PRL 131, 236904 (2023) [2] Hu, Naik, Chan, Ruan, and Louie, PNAS 120, e2314775120 (2023) |
