Coexistence of superconductivity and topological band in a van der Waals Sn1-xInxBi2Te4 crystal

TL;DR

This study demonstrates the coexistence of topological surface states and superconductivity in Sn1-xInxBi2Te4 crystals, providing a promising platform for topologically nontrivial superconductivity.

Contribution

It provides spectroscopic evidence of both topological surface states and superconductivity coexisting in a single material without interfaces.

Findings

Superconducting gap of up to 311 μeV observed.

Topological surface states coexist with superconductivity on the same surface.

Weak-coupling s-wave superconductivity indicated by vortex analysis.

Abstract

The realization of topological surface states and superconductivity within a single material platform is a crucial step toward achieving topologically nontrivial superconductivity. This can be achieved at an interface between a superconductor and a topological insulator, or within a single material that intrinsically hosts both superconductivity and topological surface states. Here we use scanning tunneling microscopy to study Sn1-xInxBi2Te4 crystals. Spectroscopic evidence reveals the coexistence of topological surface states and superconductivity on the same surface of the crystals. The Te-terminated surface exhibits a single U-shaped superconducting gap with a size of up to 311 {\mu}eV, alongside Dirac bands outside the gap. Analysis of the vortex structure and differential conductance suggests weak-coupling s-wave superconductivity. The absence of observed zero modes suggests that shifting the Fermi level closer to the Dirac point of the topological bands is necessary to realize a topological superconducting state.