Helical spin texture of surface states in topological superconductors

TL;DR

This paper investigates the helical spin textures of surface states in topological noncentrosymmetric superconductors, analyzing how spin polarization depends on spin-orbit interaction and pairing symmetry, and proposing experimental detection methods.

Contribution

It provides a detailed theoretical analysis of surface state spin textures in various topological superconductors, highlighting the influence of bulk properties and suggesting experimental tests.

Findings

Surface spin polarization is coupled to momentum in topological superconductors.

Spin polarization of flat bands is linked to bulk states at gap nodes.

Zero-bias conductance can serve as an experimental probe of surface spin textures.

Abstract

Surface states of topological noncentrosymmetric superconductors exhibit intricate helical spin textures, i.e., the spin orientation of the surface quasiparticles is coupled to their momentum. Using quasiclassical theory, we study the spin polarization of the surface states as a function of the spin-orbit interaction and superconducting pairing symmetry. We focus on two- and three-dimensional fully gapped and nodal noncentrosymmetric superconductors. For the case of nodal systems, we show that the spin polarization of the topological flat bands is controlled by the spin polarization of the bulk normal states at the bounding gap nodes. We demonstrate that the zero-bias conductance in a magnetic tunnel junction can be used as an experimental test of the surface-state spin polarization.