Multi-band Superconductivity in the Chevrel Phases SnMo6S8 and PbMo6S8

TL;DR

This study uses scanning tunnelling spectroscopy and heat capacity measurements to reveal two distinct, anisotropic superconducting gaps in Chevrel phases SnMo6S8 and PbMo6S8, confirming a two-band superconductivity scenario.

Contribution

It provides the first detailed spectroscopic and thermodynamic evidence for multi-band superconductivity in Chevrel phases SnMo6S8 and PbMo6S8, highlighting anisotropic gap features.

Findings

Two distinct superconducting gaps identified in both materials.

Gaps are strongly anisotropic and fit an anisotropic two-band BCS s-wave model.

Heat capacity measurements support the two-gap superconductivity scenario.

Abstract

Sub-Kelvin scanning tunnelling spectroscopy in the Chevrel Phases SnMo6S8 and PbMo6S8 reveals two distinct superconducting gaps with Delta_1 = 3 meV, Delta_2 ~ 1.0 meV and Delta_1 = 3.1 meV, Delta_2 ~ 1.4 meV respectively. The gap distribution is strongly anisotropic, with Delta_2 predominantly seen when scanning across unit-cell steps on the (001) sample surface. The spectra are well-fitted by an anisotropic two-band BCS s-wave gap function. Our spectroscopic data are confirmed by electronic heat capacity measurements which also provide evidence for a twin-gap scenario.