Coherent longitudinal acoustic phonon dynamics in antimony sulfide under hydrostatic pressure

Van der Waals (vdW) solids, composed of ultrathin atomic layers with weak interlayer bonding, possess unique electronic and thermal properties and exhibit sensitivity to external stimuli such as compressive strain. Understanding and manipulation of their thermal transport behavior through strain engineering is crucial to optimize thermal management and energy conversion, which still remains elusive. Here, we demonstrate pressure manipulation on cross-plane coherent longitudinal acoustic phonon (CLAP) dynamics in bulk antimony sulfide (Sb₂S₃) under hydrostatic pressure through both systematic femtosecond pump-probe spectroscopy and first-principles calculations. The experimental group velocity of CLAP increases monotonically by around $68%$ upon compression up to 5.06 GPa. First-principles calculations reveal that this dramatic change comes from the modification of phonon dispersion. Our findings shed light on the manipulation of thermal transport and energy conversion via compressive strain, which contribute to the thermal management in device engineering.