Photoexcited Electron Dynamics in Cd3As2 Revealed by Time- and Energy-Resolved Photoemission Electron Microscopy

Cd3As2, as a three-dimensional Dirac semimetal, has attracted considerable research interest because of its distinct optoelectronic and topological properties. However, simultaneous studies on the carrier dynamics in Cd3As2 in spatial, temporal, and energy dimensions are still lacking. Here, we apply photoemission electron microscopy combined with the femtosecond pump-probe technique to reveal the dynamics of the Cd3As2 nanoplate. The photoexcited electrons on the Cd3As2 surface decay fast with an average decay time of 0.68 ps. The electron dynamics are independent of the spatial location by analyzing the decay curves at different positions on the Cd3As2 nanoplate. The effect of boundary states on the relaxation process is negligible. The photoexcited electrons can relax in picoseconds, regardless of the pump or probe power. In the energy-resolved mode, the decay time of nonequilibrium electrons decreases from 7 to 0.25 ps as the energy of hot electrons increases. These results contribute to understanding the photoexcited electron behavior of Cd3As2.