Domain walls and their experimental signatures in s+is superconductors

TL;DR

This paper explores the experimental signatures of domain walls in s+is superconductors, proposing magnetic detection methods to confirm the presence of such states in hole-doped Ba$_{1-x}$K$_x$Fe$_2$As$_2$.

Contribution

It identifies unique magnetic signatures of domain walls in s+is superconductors and proposes experimental approaches to detect and confirm this state.

Findings

Domain walls in s+is superconductors can have dipole-like magnetic signatures.

Proposed experiments involve quench-induced domain walls stabilized by geometric barriers.

Magnetic signatures can be used to experimentally confirm the s+is state.

Abstract

Arguments were recently advanced that hole-doped Ba$_{1-x}$K$_x$Fe$_2$As$_2$ exhibits $s+is$ state at certain doping. Spontaneous breaking of time reversal symmetry in $s+is$ state, dictates that it possess domain wall excitations. Here, we discuss what are the experimentally detectable signatures of domain walls in $s+is$ state. We find that in this state the domain walls can have dipole-like magnetic signature (in contrast to the uniform magnetic signature of domain walls $p+ip$ superconductors). We propose experiments where quench-induced domain walls can be stabilized by geometric barriers and be observed via their magnetic signature or their influence on the magnetization process, thereby providing an experimental tool to confirm $s+is$ state.