Magnetic Intragap States and Mixed Parity Pairing at the Edge of Spin-Triplet Superconductors

TL;DR

This paper investigates how a spontaneous magnetic moment can form at the edge of spin-triplet superconductors due to subdominant pairing channels, revealing the microscopic mechanism involving non-unitary states and Andreev bound-states.

Contribution

It combines numerical and Ginzburg-Landau methods to show how edge magnetic moments arise from mixed parity pairing and inhomogeneous non-unitary states in spin-triplet superconductors.

Findings

Magnetic moments can spontaneously appear at the superconductor edge.

Potential barriers induce non-unitary superconducting states near the boundary.

Edge spin polarization results from lifting spin degeneracy of Andreev bound-states.

Abstract

We show that a spontaneous magnetic moment may appear at the edge of a spin-triplet superconductor if the system allows for pairing in a subdominant channel. To unveil the microscopic mechanism behind such effect we combine numerical solution of the Bogoliubov-De Gennes equations for a tight-binding model with nearest-neighbor attraction, and the symmetry based Ginzburg-Landau approach. We find that a potential barrier modulating the electronic density near the edge of the system leads to a non-unitary superconducting state close to the boundary where spin-singlet pairing coexists with the dominant triplet superconducting order. We demonstrate that the spin polarization at the edge appears due to the inhomogeneity of the non-unitary state and originates in the lifting of the spin-degeneracy of the Andreev bound-states.