Magnetic signatures of domain walls in $s+is$ and $s+id$ superconductors: observability and what that can tell us about the superconducting order parameter

Abstract

One of the defining features of spontaneously broken time-reversal symmetry (BTRS) is the existence of domain walls, the detection of which would be strong evidence for such systems. There is keen interest in BTRS currently, in part, due to recent muon spin rotation experiments, which have pointed towards ${\text{Ba}}_{1-x}{\text{K}}_x{\text{Fe}}_2{\text{As}}_2$ exhibiting a remarkable case of $s$-wave superconductivity with spontaneously broken time-reversal symmetry. A key question, however, is how to differentiate between the different theoretical models which describe such a state. Two particularly popular choices of model are $s+is$ and $s+id$ superconducting states. In this paper, we obtain solutions for domain walls in $s+is$ and $s+id$ systems, including the effects of lattice anisotropies. We show that, in general, both models exhibit spontaneous magnetic field, that extend along the entire length of the domain wall. We demonstrate the qualitative difference between the magnetic signatures of $s+is$ and $s+id$ domain walls and propose a procedure to extract the superconducting pairing symmetry from the magnetic-field response of domain walls.

8 pages, 5 figures

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• Chiral CP^2 skyrmions in three-band superconductors
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• Magnetic response of nematic superconductors: skyrmion stripes and their signatures in muon spin relaxation experiments
• Time-reversal symmetry breaking from lattice dislocations in superconductors
• Magnetic field behaviour in $s+is$ and $s+id$ superconductors: twisting of applied and spontaneous fields
• Vortex lattices and critical fields in anisotropic superconductors
• Ultrasound evidence for multicomponent superconducting order parameter in Ba${}_{1-x}$K${}_x$Fe${}_2$As${}_2$ with electron quadrupling phase
• Spontaneous edge corner currents in $s+is$ superconductors and time reversal symmetry breaking surface states