Full superconducting gap in the candidate topological superconductor In$_{1-x}$Pb$_x$Te for x = 0.2

TL;DR

This study investigates the superconducting gap structure of In$_{0.8}$Pb$_{0.2}$Te, revealing a fully gapped behavior that suggests conventional pairing, with implications for its topological superconductivity potential.

Contribution

The paper provides experimental evidence of a fully gapped superconducting state in In$_{0.8}$Pb$_{0.2}$Te, challenging the presence of topologically nontrivial pairing in this compound.

Findings

Fully gapped BCS-like behavior observed

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

Possible $A_{1u}$ odd-parity pairing remains plausible

Abstract

High-pressure synthesis techniques have allowed for the growth of samples on the indium-rich side of (Pb,In)Te, which have increased superconducting transition temperatures compared to lead-rich compounds. In this study we present measurements of the temperature dependence of the London penetration depth $\Delta \lambda(T)$ in the compound In$_{0.8}$Pb$_{0.2}$Te, which shows a bulk $T_{c,onset}$ of $\sim4.75$ K. The results indicate fully gapped BCS-like behavior, ruling out odd-parity, topologically nontrivial $A_{2u}$ pairing; however, odd-parity $A_{1u}$ pairing is still possible. Critical field values measured below 1 K and other superconducting parameters are also presented.