Proximity effect at the superconductor - topological insulator interface

TL;DR

This paper investigates how superconductivity is induced at the interface between a topological insulator and an s-wave superconductor, revealing a complex interplay of s-wave and p-wave pairing components and parameter renormalization.

Contribution

It develops a microscopic and effective low-energy model to describe the proximity effect at the TI-superconductor interface, highlighting the conditions for observing induced superconductivity.

Findings

Induced pairing near the Dirac point is primarily s-wave, with p-wave components away from it.

Significant parameter renormalization occurs due to the superconductor proximity.

Observation of induced superconductivity requires tuning the chemical potential close to the Dirac point.

Abstract

We study the excitation spectrum of a topological insulator in contact with an s-wave superconductor, starting from a microscopic model, and develop an effective low-energy model for the proximity effect. In the vicinity of the Dirac cone vertex, the effective model describing the states localized at the interface is well approximated by a model of Dirac electrons experiencing superconducting s-wave pairing. Away from the cone vertex, the induced pairing potential develops a p-wave component with a magnitude sensitive to the structure of the interface. Observing the induced s-wave superconductivity may require tuning the chemical potential close to the Dirac point. Furthermore, we find that the proximity of the superconductor leads to a significant renormalization of the original parameters of the effective model describing the surface states of a topological insulator.