腾讯会议ID：379-192-423
会议密码：0514
主持人：孟胜 研究员
联系人：傅琦 (fuqi@iphy.ac.cn)
Abstract:
Time-resolved methods based on ultrafast laser enable the excitation of electronic systems into nonequilibrium states, and allow for the probe complex many-body effects and the control of transient metastable phases, which are inaccessible in steady-state experiments. In this talk, I will first briefly introduce our earlier work on ultrafast charge-density-wave dynamics by time-resolved ARPES (EUV). Then I will present our recent progresses by time-resolved optical spectroscopy (VI-NIR). We observe interband-transition-induced high-energy electronic excitations in a bilayer nickelate superconductor La3Ni2O7, associated with two density-wave gaps and correlated with distinct coherent phonons. The charge-transfer gap in cuprate parent compounds, which has been proposed to anticorrelate with superconducting transition, undergoes ultrafast renormalization under photoexcitation. The interfacial electron-phonon coupling is directly observed in FeSe/STO. Notably, ultrafast laser pulses with circular polarization enable the excitation and monitoring of chirality dependent valleytronics, coherent optical Stark effect and biexcitons in 2D transition metal dichalcogenides. In the end, I will introduce low-energy excitations probed by terahertz (THz), including the oxygen vacancy modes in an electrolyte material ZrO2, and low-frequency phonon dynamics in black phosphorus.
Brief CV of Dr. Haiyun Liu:
Dr. Haiyun Liu received his Ph.D degree in condensed matter physics in 2010 from Institute of Physics, Chinese Academy of Sciences, under the supervision of Prof. Xingjiang Zhou. After graduation, he worked as a postdoctoral fellow and beamline scientist in Prof. Andrea Cavalleri's group at University of Hamburg and Max Planck Research Department for Structural Dynamics (MPSD). In 2019, he joined Beijing Academy of Quantum Information of Sciences as an associate professor. His research focuses on ultrafast dynamics of nonequilibrium states, including many body effects and transient phase transitions in high-temperature superconductors, two-dimensional transition metal dichalcogenides, density-wave materials, and related systems.