Polarization Anisotropy of Ultrafast Electronic Dynamics in AB-Stacked Rhenium Disulfide

Abstract

Revealing transient electronic properties in anisotropic 2D materials is a prerequisite for developing ultrafast optoelectronic functional devices. Here, the ultrafast electronic dynamics of polarization anisotropy for the AB-stacked rhenium disulfide (ReS₂) are studied using time- and energy-resolved photoemission electron microscopy. The ultrafast electronic relaxation process exhibits sensitive layer-dependent polarization anisotropy. The linear dichroism of the ultrafast electronic dynamics is also measured, indicating that the polarization anisotropy is determined by the fast process on the sub-picosecond scale. With ab initio theory calculations, it is confirmed that the ultra-sensitive layer dependence of the lifetime of the fast process originates from a stronger interlayer coupling in the K-Γ direction (along the b-axis) of ReS₂. Further, by analyzing the time-resolved photoemission energy spectrum, distinct “fast” and “slow” regimes are found in the ultrafast dynamics of excited electrons with different energies. The corresponding energy windows also show substantial polarization anisotropy, which is associated with the linear dichroism of the electron-phonon coupling in the AB-stacked ReS₂. This work has implications for the design of angle-sensitive optoelectronic functional devices with the AB-stacked ReS₂.