Scanning tunneling microscopy of superconducting topological surface states in Bi$_2$Se$_3$

TL;DR

This study uses scanning tunneling microscopy to investigate superconducting topological surface states in Bi$_2$Se$_3$, revealing induced superconductivity, oscillations in the density of states, and evidence of an inverse topological proximity effect.

Contribution

It demonstrates the presence of induced superconductivity and oscillatory behavior in the topological surface states of Bi$_2$Se$_3$ with superconducting islands, highlighting an inverse proximity effect.

Findings

Induced superconductivity in topological surface states with a coherence length of ~540 nm.

Observation of density of states oscillations above the superconducting gap.

Evidence of an inverse topological proximity effect on the islands.

Abstract

In this paper we present scanning tunneling microscopy of a large $\textrm{Bi}_2\textrm{Se}_3$ crystal with superconducting PbBi islands deposited on the surface. Local density of states measurements are consistent with induced superconductivity in the topological surface state with a coherence length of order 540 nm. At energies above the gap the density of states exhibits oscillations due to scattering caused by a nonuniform order parameter. Strikingly, the spectra taken on islands also display similar oscillations along with traces of the Dirac cone, suggesting an inverse topological proximity effect.