Massive suppression of proximity pairing in topological (Bi$_{1-x}$Sb$_{x})_2$Te$_3$ films on niobium

TL;DR

This study reveals a significant suppression of proximity-induced superconductivity in topological (Bi$_{1-x}$Sb$_{x})_2$Te$_3$ films on niobium, highlighting challenges in achieving topological superconductivity in nearly intrinsic topological insulators.

Contribution

The paper demonstrates that bulk insulating topological (Bi$_{1-x}$Sb$_{x})_2$Te$_3$ films exhibit a massive suppression of proximity pairing when interfaced with niobium, contrasting with previous findings in doped systems.

Findings

Giant attenuation of surface superconductivity in (Bi$_{1-x}$Sb$_{x})_2$Te$_3$ films on Nb

Quantified superconducting gaps show significant suppression compared to doped Bi$_2$Se$_3$/Nb

Limitations identified for realizing topological superconductivity in intrinsic systems

Abstract

Interfacing bulk conducting topological Bi$_2$Se$_3$ films with s-wave superconductors initiates strong superconducting order in the nontrivial surface states. However, bulk insulating topological (Bi$_{1-x}$Sb$_{x})_2$Te$_3$ films on bulk Nb instead exhibit a giant attenuation of surface superconductivity, even for films only two-layers thick. This massive suppression of proximity pairing is evidenced by ultrahigh-resolution band mappings and by contrasting quantified superconducting gaps with those of heavily n-doped topological Bi$_2$Se$_3$/Nb. The results underscore the limitations of using superconducting proximity effects to realize topological superconductivity in nearly intrinsic systems.