Pressure-driven layer-dependent phase transitions and enhanced interlayer coupling in PdSe2 crystals

Pressure exerts a profound influence on atomic configurations and interlayer interactions, thereby modulating the electronic and structural properties of materials. While high pressure has been observed to induce a structural phase transition in bulk PdSe₂ crystals, leading to a transition from semiconductor to metal, the high-pressure behavior of few-layer PdSe₂ remains elusive. Here, employing diamond anvil cell (DAC) techniques and high-pressure Raman spectroscopy, we investigate the structural evolution of layer-dependent PdSe₂ under high pressure. We reveal that pressure significantly enhances interlayer coupling in PdSe₂, driving structural phase transitions from an orthorhombic to a cubic phase. We demonstrate that PdSe₂ crystals exhibit distinct layer-dependent pressure thresholds during the phase transition, with the decrease of transition pressure as the thickness of PdSe₂ increases. Furthermore, our results of polarized Raman spectra confirm a reduction in material anisotropy with increasing pressure. This study offers crucial insights into the structural evolution of layer-dependent van der Waals materials under pressure, advancing our understanding of their pressure-induced behaviors.