Pressure Manipulation of Interlayer Interactions and Ultrafast Carrier Dynamics in Few-Layer MoS2

Abstract

Van der Waals interlayer interactions play a crucial role in the electronic structure and ultrafast carrier dynamics in two-dimensional transition metal dichalcogenides and their heterostructures. In this work, we provide subtle manipulation and quantification of interlayer interactions in few-layer MoS2 using hydrostatic pressure generated by a diamond anvil cell. Systematic investigation of ultrafast carrier relaxation dynamics of few-layer MoS2 under hydrostatic pressure via femtosecond broadband transient absorption spectroscopy is demonstrated for the first time. Specifically, during compression from 0.05 up to 3.20 GPa, the interlayer interactions are monotonically enhanced with an increase of the valence band maximum splitting from 156 to 168 meV, and the corresponding carrier relaxation dynamics of hot carrier cooling and exciton dissociation are found to get faster simultaneously with a decrease of lifetime from 1.0 to 0.6 ps and 5.5 to 3.0 ps, respectively. When the pressure is released, both the spectra and dynamics are fully recovered. At around 1.22 GPa, an unexpected turning point occurs and breaks the evolution of both the interlayer interactions and carrier relaxation dynamics into two stages, which can be attributed to electronic structure changes induced by hydrostatic pressure. Based on these findings, intrinsic relations among interlayer interactions, ultrafast carrier dynamics, and electronic structure can be drawn, which pave the way for a deeper understanding of the underlying many-body physics and facilitate promising applications of two-dimensional transition metal dichalcogenides and their heterostructures.