Vortex supercurrent inversion by frequency-symmetry conversion of Cooper pairs

TL;DR

This paper theoretically shows that vortex supercurrents can be reversed near the surface of certain superconductors due to odd-frequency Cooper pairs and surface bound states, with differences observed between s-wave and p_z-wave types.

Contribution

It reveals the mechanism of vortex supercurrent inversion via frequency-symmetry conversion of Cooper pairs and surface Andreev bound states in three-dimensional superconductors.

Findings

Vortex supercurrent is reversed near the surface of p_z-wave superconductors.

Surface Andreev bound states cause splitting of zero-energy states.

Supercurrent behavior differs between s-wave and p_z-wave superconductors.

Abstract

We theoretically demonstrate that the vortex supercurrent can be reversed by odd-frequency Cooper pairs accompanied by surface Andreev bound states. The surface of a three-dimensional superconductor pierced by a flux quantum is considered. We compare the vortex supercurrents near the surface of the spin-singlet $s$-wave and spin-triplet $p_z$-wave superconductors using quasiclassical Eilenberger theory, where the surface is perpendicular to the $z$ direction. We demonstrate that the vortex supercurrent near the surface of a $p_z$-wave superconductor is reversed compared to those far from the surface, whereas that of an $s$-wave superconductor is not. The splitting of the zero-energy states caused by the interference of the surface Andreev bound states and Caroli-de Gennes-Matricon modes is demonstrated.