Ultrafast Electron Cooling and Decay in Monolayer WS<sub>2</sub> Revealed by Time- and Energy-Resolved Photoemission Electron Microscopy
Yaolong Li, Wei Liu, Yunkun Wang, Zhaohang Xue, Yu‐Chen Leng, Aiqin Hu, Hong Yang, Ping‐Heng Tan, Yunquan Liu, Hiroaki Misawa, Quan Sun, Yunan Gao, Xiaoyong Hu, Qihuang Gong
Abstract
by time- and energy-resolved photoemission electron microscopy (PEEM). Electron cooling in the Q valley of the conduction band is clearly resolved in energy and time, on a time scale of 0.3 ps. Electron decay is mainly via a defect trapping process on a time scale of several picoseconds. We observed that the trap states can be produced and increased by laser illumination under an ultrahigh vacuum, and the higher local optical-field intensity led to the faster increase of trap states. The enhanced defect trapping could significantly modify the carrier dynamics and should be paid attention to in photoemission experiments for two-dimensional materials.