Superconducting and structural properties of the type-I superconductor PdTe2 under high pressure

Abstract

The transition metal dichalcogenide $\mathrm{Pd}{\mathrm{Te}}_{2}$ has attractive features based on its classification as a type-II Dirac semimetal and the occurrence of type-I superconductivity, providing a platform for discussion of a topological superconductor. Our recent work revealed that type-I superconductivity persists up to pressures of $\ensuremath{\sim}2.5$ GPa and the superconducting transition temperature ${T}_{\mathrm{c}}$ reaches a maximum at around 1 GPa, which is inconsistent with the theoretical prediction. To understand its nonmonotonic variation and investigate superconductivity at higher pressures, we performed structural analysis by x-ray diffraction at room temperature below 8 GPa and electrical resistivity measurements at low temperatures from 1 to 8 GPa. With regard to the superconductivity beyond 1 GPa, the monotonic decrease in ${T}_{\mathrm{c}}$ is reproduced without any noticeable anomalies; ${T}_{\mathrm{c}}$ changes from 1.8 K at 1 GPa to 0.82 K at 5.5 GPa with $d{T}_{\mathrm{c}}/dP\ensuremath{\sim}\ensuremath{-}0.22$ K/GPa. The crystal structure with space group $P\overline{3}m1$ is stable in the pressure range we examined. On the other hand, the normalized pressure-strain analysis (finite strain analysis) indicates that the compressibility changes around 1 GPa, suggesting that a Lifshitz transition occurs. We here discuss the effect of pressure on the superconducting and structural properties based on the comparison of these experimental results.