Time-reversal symmetry breaking from lattice dislocations in superconductors

TL;DR

This study shows that lattice dislocations in unconventional superconductors can induce localized supercurrents, leading to local time-reversal symmetry breaking, regardless of the specific pairing symmetry.

Contribution

The paper provides a microscopic theoretical analysis of how dislocations induce local time-reversal symmetry breaking in various types of unconventional superconductors.

Findings

Dislocations induce localized supercurrents in superconductors.

Time-reversal symmetry breaking occurs locally around dislocations.

The effect is present across different pairing symmetries.

Abstract

Spontaneous generation of time-reversal symmetry breaking in unconventional superconductors is currently a topic of considerable interest. While chiral superconducting order is often assumed to be the source of such signatures, they can sometimes also arise from nonmagnetic disorder. Here we perform a theoretical study of the impact of dislocations on the superconducting order parameter within a microscopic one-band model which, in the homogeneous case, features either extended $s$-wave, $d$-wave, or $s+id$-wave superconductivity depending on the electron concentration. We find that the dislocations minimize their impact on the superconducting condensate by inducing localized supercurrents pinned by the dislocations, even well outside the $s+id$ regime. We map out the parameter and density dependence of the induced currents. From these results we conclude that quite generically unconventional superconductors hosting dislocations tend to break time-reversal symmetry locally.