Unusual nature of fully-gapped superconductivity in In-doped SnTe

TL;DR

This study investigates the superconducting properties of In-doped SnTe, revealing a change in pairing mechanism across a critical doping level and an unexpected enhancement of Tc with impurity scattering in a specific phase.

Contribution

It provides the first detailed phase diagram of Sn_{1-x}In_{x}Te, showing how superconductivity and structural phases are interconnected and how impurity effects influence Tc.

Findings

Superconducting transition temperature Tc varies with In doping level.

Tc is strongly enhanced by impurity scattering below the critical doping.

A change in electron pairing mechanism occurs across the critical doping xc.

Abstract

The superconductor Sn_{1-x}In_{x}Te is a doped topological crystalline insulator and has become important as a candidate topological superconductor, but its superconducting phase diagram is poorly understood. By measuring about 50 samples of high-quality, vapor-grown single crystals, we found that the dependence of the superconducting transition temperature Tc on the In content x presents a qualitative change across the critical doping xc ~ 3.8%, at which a structural phase transition takes place. Intriguingly, in the ferroelectric rhombohedral phase below the critical doping, Tc is found to be strongly ENHANCED with impurity scattering. It appears that the nature of electron pairing changes across xc in Sn_{1-x}In_{x}Te.