Superconductivity in the doped topological insulator Cu$_x$Bi$_2$Se$_3$ under high pressure

TL;DR

This study investigates how high pressure affects the superconducting properties of Cu$_x$Bi$_2$Se$_3$, revealing a suppression of superconductivity and insights into its pairing symmetry, suggesting possible spin-triplet pairing.

Contribution

First high-pressure single crystal measurements of Cu$_x$Bi$_2$Se$_3$ revealing pressure effects on superconductivity and pairing symmetry clues.

Findings

Superconductivity decreases smoothly under pressure.

Upper critical field data collapse onto a universal curve.

Evidence suggests spin-triplet superconductivity, but anisotropic spin-singlet cannot be ruled out.

Abstract

We report a high-pressure single crystal study of the topological superconductor Cu$_x$Bi$_2$Se$_3$. Resistivity measurements under pressure show superconductivity is depressed smoothly. At the same time the metallic behavior is gradually lost. The upper critical field data $B_{c2}(T)$ under pressure collapse onto a universal curve. The absence of Pauli limiting and the comparison of $B_{c2}(T)$ to a polar state function point to spin-triplet superconductivity, but an anisotropic spin-singlet state cannot be discarded completely.