Pressure‐Tunable Coherent Terahertz Emission in a Two‐Dimensional Gallium Telluride Crystal

ABSTRACT Coherent terahertz (THz) emission driven by ultrafast light–matter interactions is central to the development of advanced photonic and optoelectronic technologies. However, enhancing THz emission efficiency remains challenging due to the intrinsic dependence of generation mechanisms‐optical rectification (OR) and shift current (SC)‐on fixed material properties such as lattice symmetry and electronic structure. Here, we demonstrate hydrostatic pressure as an effective in situ control parameter for modulating THz emission in a two‐dimensional GaTe crystal. Using ultrafast THz emission spectroscopy in a diamond anvil cell (DAC), we observe a more than 13‐fold enhancement in THz output under compression. By tuning the excitation wavelength, we uncover a pressure‐induced transition from bound‐electron OR to free‐carrier SC, featuring a systematic forward time shift in THz waveform. First‐principles calculations reveal that the enhanced emission and time shift originate from pressure‐driven changes in resonance frequency and charge density. These results highlight hydrostatic pressure as a powerful means to tailor nonlinear light–matter interactions and optimize coherent THz emission in low‐dimensional systems.