Topological spin-current in non-centrosymmetric superconductors

TL;DR

This paper investigates how topologically protected helical edge modes in non-centrosymmetric superconductors enable spin-polarized currents, revealing potential for spintronic applications in topological superconducting states.

Contribution

It demonstrates the emergence of topologically nontrivial superconducting states with helical edge modes and their role in generating spin-polarized currents at interfaces.

Findings

Helical edge modes are topologically protected in certain superconducting states.

Incident angle-dependent spin-polarized currents are observed due to edge modes.

Weak magnetic fields enhance the spin polarization of the current.

Abstract

We study the spin transport properties of the non-centrosymmetric superconductor with time-reversal-symmetry where spin-triplet $(p_{x} \pm i p_{y})$-wave and spin-singlet s-wave pair potential can mix each other. We show that when the amplitude of $(p_{x} \pm ip_{y})$-wave pair potential is larger than that of s-wave one, the superconducting state belongs to the topologically nontrivial class analogous to the quantum spin Hall system, and the resulting helical edge modes as Andreev bound states are topologically protected. We find that the incident angle dependent spin polarized current flows through the interface due to the presence of the helical edge modes. With a weak magnetic field, also the angle-integrated current is strongly spin polarized.