High-pressure study of the basal-plane anisotropy of the upper critical field of the topological superconductor SrxBi2Se3

TL;DR

This study investigates how high pressure affects the anisotropy of the upper critical magnetic field in the topological superconductor Sr$_{0.15}$Bi$_2$Se$_3$, revealing the robustness of its unconventional superconducting state with broken rotational symmetry.

Contribution

It provides the first high-pressure transport measurements of $B_{c2}(T)$ in Sr$_{0.15}$Bi$_2$Se$_3$, demonstrating the reinforcement of basal-plane anisotropy under pressure.

Findings

Superconductivity is suppressed at around 3.5 GPa.

Basal-plane anisotropy $B_{c2}^a/B_{c2}^{a^*}$ increases from 3.2 to about 5 under pressure.

Unconventional superconducting state with broken rotational symmetry remains robust under pressure.

Abstract

We report a high-pressure transport study of the upper-critical field, $B_{c2}(T)$, of the topological superconductor Sr$_{0.15}$Bi$_2$Se$_3$ ($T_c = 3.0$ K). $B_{c2}(T)$ was measured for magnetic fields directed along two orthogonal directions, $a$ and $a^*$, in the trigonal basal plane. While superconductivity is rapidly suppressed at the critical pressure $p_c \sim 3.5$ GPa, the pronounced two-fold basal-plane anisotropy $B_{c2}^a/B_{c2}^{a^*} = 3.2$ at $T=0.3$ K, recently reported at ambient pressure (Pan et al., 2016), is reinforced and attains a value of $\sim 5$ at the highest pressure (2.2 GPa). The data reveal that the unconventional superconducting state with broken rotational symmetry is robust under pressure.