# Superconductivity under pressure in the Dirac semimetal PdTe2

## TL;DR

This study investigates how applying pressure up to 2.5 GPa affects the superconducting properties of the Dirac semimetal PdTe2, revealing non-monotonous changes in critical temperature and robust surface superconductivity linked to topological states.

## Contribution

It provides the first detailed high-pressure phase diagram of PdTe2's superconductivity, highlighting the enhancement of surface superconductivity and potential topological effects under pressure.

## Key findings

- Superconducting transition temperature peaks at 0.91 GPa.
- Surface superconductivity persists beyond bulk critical fields.
- Surface Tc exceeds bulk Tc at pressures above 1.41 GPa.

## Abstract

The Dirac semimetal PdTe$_2$ was recently reported to be a type-I superconductor ($T_c = $1.64 K, $\mu_0 H_c (0) = 13.6$ mT) with unusual superconductivity of the surface sheath. We here report a high-pressure study, $p \leq 2.5$ 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. The critical field of bulk superconductivity in the limit $T \rightarrow 0$, $H_c(0,p)$, follows a similar trend and consequently the $H_c(T,p)$-curves under pressure collapse on a single curve: $H_c(T,p)=H_c(0,p)[1-(T/T_c(p))^2]$. 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 $p \geq 1.41$ GPa the superconducting transition temperature at the surface $T_c^S$ is larger than $T_c$ of the bulk. Therefore surface superconductivity may possibly have a non-trivial nature and is connected to the topological surface states detected by ARPES. 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.