Half-metallic Surface States and Topological Superconductivity in NaCoO$_2$ from first principles

TL;DR

This paper predicts a half-metallic surface state in NaCoO2 with a helical spin texture, proposing it as a platform for topological superconductivity and Majorana fermions when coupled with a superconductor.

Contribution

First-principles calculations reveal a novel half-metallic surface state in NaCoO2, enabling potential topological superconductivity and Majorana fermions.

Findings

Half-metallic surface state with a single Fermi surface

Helical spin texture similar to topological insulators

Potential realization of topological superconductivity

Abstract

Based on first-principles calculations, we predict a half-metallic surface state in layered bulk insulator NaCoO2, with tunable surface hole concentration. The half-metallic surface has a single Fermi surface with a helical spin texture, similar to the surface state of topological insulators, but with the key difference of time-reversal symmetry breaking in the present case. We propose the realization of topological superconductivity and Majorana fermions when the half-metallic surface states are in proximity contact with a conventional superconductor.