报告时间：2月19日（周三）上午10:00
报告地点：唐仲英楼A313
报告人简介：
刘海云博士，2005年毕业于上海复旦大学物理系，获得学士学位；同年加入中国科学院物理研究所超导实验室，于2010年获得理学博士学位；2010-2013年在德国汉堡自由电子激光中心与汉堡大学从事博士后研究；2014年获得束线科学家位置。主要研究: 角分辨光电子能谱（angle-resolved photoemission spectroscopy, ARPES）与时间分辨角分辨光电子能谱(time-resolved ARPES, trARPES)系统研制, 超导材料（包括铜基与铁基超导体）合成与电子结构研究，电荷密度波（charge-density-wave）材料以及光致相变瞬态电子结构研究。在Nature, PRL, PRB等刊物发表文献20余篇。
报告简介：
Angle-resolved photoemission spectroscopy (ARPES) is a powerful tool of probing electronic structures in solids, however static/conventional ARPES fails to visualize ultrafast dynamic processes and interactions, which are fundamental to understand intrinsic physics in condensed matter, e.g., light-matter interaction, electron-electron interplay and electron coupling with various collective modes. To directly study such interesting phenomena, one of the directions is time- and angle-resolved photoemission spectroscopy (trARPES), by implementing ultrafast pump-probe beams: a first infrared (IR) pulse as pump to stimulate/drive the system, and then a second ultraviolet (UV) / extremely ultraviolet (XUV) pulse as probe to detect transient electronic states from femtosecond to picosecond time scales.
Here I will first briefly introduce our newly developed high resolution trARPES, based on THz/MIR pump and XUV probe. The idea is to resonantly drive phase transitions by intensed THz/MIR pulses, thus control dynamic processes in strongly correlated electron systems and directly investigate the novel transient states by photoemission. Then I will talk about its applications and perspectives with three different hot topics: (1) Photon-driven insulator-to-metal transition and collective modes in charge-density-wave (CDW) materials. (2) Hot-carrier multiplication. Is graphene a good candidate for highly efficient solar cells? (3) Light-induced superconductivity, a possible way of realizing high-temperature superconductors