Enhanced superconductivity near a pressure-induced quantum critical point of strongly coupled charge density wave order in 2H-Pd_0.05TaSe₂

Interplay between charge density wave (CDW) order and superconductivity (SC) in quasi-two-dimensional materials remains poorly understood due to their diverse experimental varieties. Here, we investigate the pressure-dependent electrical transport and Raman scattering spectra of 2H-Pd_0.05TaSe₂, which exhibits a CDW transition at T_CDW = 115 K and a superconducting transition at T_c = 2.6 K at ambient pressure conditions. As pressure increases, T_CDW, identified by the resistivity anomaly, shifts towards lower temperatures and approaches zero at a critical pressure of P_c ~ 21.5 GPa. At this critical pressure, both T_c and upper critical field H_c2 reach their maximum values of ~ 8.5 K and ~ 6.4 T, respectively. Analysis of the Raman scattering spectra demonstrates that increasing pressure systematically suppresses both the two-phonon spectral weight above T_CDW and the CDW amplitudon energies below T_CDW, leading to their simultaneous disappearance at P_c. These observations provide direct evidence for the formation of a CDW quantum critical point (QCP) at P_c, indicating that charge and lattice fluctuations associated with the QCP of strongly coupled CDW order may enhance SC in pressurized 2H-Pd_0.05TaSe₂.