Robustness of chiral surface current and subdominant $s$-wave Cooper pairs

TL;DR

This study investigates how surface roughness affects chiral surface currents in superconductors, finding that the presence of subdominant s-wave pairs induced by disorder can preserve the current's robustness.

Contribution

It reveals that subdominant s-wave Cooper pairs induced by disorder are key to maintaining chiral surface current robustness in certain superconductors.

Findings

Chiral surface current robustness depends on induced s-wave pairs.

Subdominant s-wave pairs act as an effective pair potential.

Chiral currents in specific superconductors are robust against surface roughness.

Abstract

The robustness of the chiral surface current of chiral superconductors against surface roughness is studied utilizing the quasiclassical Eilenberger theory. We consider the general chiral superconductors where the pair potential is given by the spherical harmonics $Y_l^m$ such that $(l,m)=(1, \pm1)$ state corresponds to an ($p_x \pm ip_y$)-wave superconductor. The self-consistent calculations demonstrate that the robustness of the chiral current is determined by whether subdominant $s$-wave Cooper pairs are induced by disorder. The induced $s$-wave pairs act as an effective pair potential. As a result, the spontaneous chiral current of ($p_x+ip_y$)- and ($d_{x^2-y^2}+id_{xy}$)-wave superconductors are robust against the roughness because the subdominant $s$-wave Cooper pairs are present.