Nodeless superconducting gap in the candidate topological superconductor Sn$_{1-x}$In$_x$Te for x = 0.7

TL;DR

This study investigates the superconducting gap structure of Sn$_{1-x}$In$_x$Te with x=0.7, revealing a nodeless, fully gapped behavior consistent with conventional BCS superconductivity, and discusses implications for pairing symmetry.

Contribution

First measurement of the London penetration depth in high-pressure synthesized Sn$_{1-x}$In$_x$Te at x=0.7, demonstrating a fully gapped superconducting state and constraining pairing symmetry.

Findings

Fully gapped BCS-like behavior observed

Odd-parity $A_{2u}$ pairing ruled out

Critical fields and superconducting parameters measured

Abstract

High-pressure synthesis techniques have allowed for the growth of Sn$_{1-x}$In$_x$Te samples beyond the ambient In-saturation limit of $x$ = 0.5 (T$_c \sim$ 4.5 K). In this study, we present measurements of the temperature dependence of the London penetration depth $\Delta\lambda(T)$ in this superconducting doped topological insulator for $x$ = 0.7, where T$_{c,onset}\approx 5$ K. The results indicate fully gapped BCS-like behavior, ruling out odd-parity $A_{2u}$ pairing; however, odd-parity $A_{1u}$ pairing is still possible. Critical field values measured below 1 K and other superconducting parameters are also presented.