Edge superconducting state in attractive U Kane-Mele-Hubbard model

TL;DR

This paper predicts an edge-specific superconducting state in a topological insulator model with attractive interactions, revealing a two-step phase transition from insulator to superconductor.

Contribution

It introduces the concept of edge superconducting state (ESS) in the Kane-Mele-Hubbard model, a novel phenomenon not previously reported.

Findings

Edge superconductivity appears immediately with nonzero attraction U.

A critical U_c marks the transition to a bulk superconductor.

The ESS is linked to the unique energy dispersion of topological insulators.

Abstract

We theoretically investigate the phase transition from topological insulator (TI) to superconductor in the attractive U Kane-Mele-Hubbard model with self-consistent mean field method. We demonstrate the existence of edge superconducting state (ESS), in which the bulk is still an insulator and the superconductivity only appears near the edges. The ESS results from the special energy dispersion of TI, and is a general property of the superconductivity in TI. The phase transition in this model essentially consists of two steps. When the attractive U becomes nonzero, ESS appears immediately. After the attractive U exceeds a critical value $U_c$, the whole system becomes a superconductor. The effective model of the ESS has also been discussed and we believe that the conception of ESS can be realized in atomic optical lattice system.