Superconductivity under pressure in the Dirac semimetal PdTe₂

The Dirac semimetal PdTe₂ was recently reported to be a type-I superconductor (T_c = 1.64 K, μ₀H_c(0)= 13.6 mT) with unusual superconductivity of the surface sheath. We here report a high-pressure study, p ≤ 2.5 GPa, of the superconducting phase diagram extracted from ac-susceptibility and transport measurements on single crystalline samples. T_c(p ) shows a pronounced non-monotonous variation with a maximum T_c = 1.91 K around 0.91 GPa, followed by a gradual decrease to 1.27 K at 2.5 GPa. Surface superconductivity is robust under pressure as demonstrated by the large superconducting screening signal that persists for applied dc-fields H_a > H_c. Surprisingly, for p ≥ 1.41 GPa the superconducting transition temperature at the surface T_c is larger than T_c of the bulk. Therefore surface superconductivity may possibly have a non-trivial topological nature. We compare the measured pressure variation of T_c with recent results from band structure calculations and discuss the importance of a Van Hove singularity.