Proximity-induced unconventional superconductivity in topological insulators

TL;DR

This paper investigates how different superconductors induce various unconventional pairing states in topological insulators, revealing complex modifications to surface states and pairing symmetries.

Contribution

It classifies proximity-induced superconducting pairings in TI-SC hybrids, highlighting the emergence of odd-frequency and odd-orbital pairings for various superconductor symmetries.

Findings

Induces odd-frequency pairing in TI surface states.

Couples spin-singlet and spin-triplet pairings via Dirac surface states.

Modifies the density of states in the topological insulator surface layer.

Abstract

We study and classify the proximity-induced superconducting pairing in a topological insulator (TI)-superconductor (SC) hybrid structure for SCs with different symmetries. The Dirac surface state gives a coupling between spin-singlet and spin-triplet pairing amplitudes as well as pairing that is odd in frequency for p-wave SCs. We also find that all SCs induce pairing that is odd in both frequency and orbital (band) index, with oddness in frequency and orbital index being completely interchangeable. The different induced pairing amplitudes significantly modifies the density of states in the TI surface layer.