Enhanced superconductivity near a pressure-induced quantum critical point of strongly coupled charge density wave order in 2H-Pd0.05TaSe2

Abstract

Abstract 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-Pd0.05TaSe2, 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-Pd0.05TaSe2.