Fulde-Ferrell state in ferromagnetic chiral superconductor with magnetic domain wall

TL;DR

This paper investigates how ferromagnetic domains induce chiral superconducting domains and a Fulde-Ferrell-like state in heavy fermion systems, revealing unique current behaviors at domain walls and surfaces.

Contribution

It demonstrates that magnetic domains induce chiral superconducting domains and stabilize a Fulde-Ferrell-like state through domain wall and surface current interactions.

Findings

Domain walls host currents flowing opposite to naive expectations due to unpaired electrons.

Surface and domain wall currents can add constructively, leading to a net current.

A Fulde-Ferrell-like superconducting state is stabilized below the transition temperature.

Abstract

Motivated by the recent theoretical and experimental progress in the heavy fermion system UCoGe, we study ferromagnetic chiral superconductors in the presence of magnetic domains. Within mean field approximations, it is shown that chiral superconducting domains are naturally induced by the ferromagnetic domains. The domain wall current flows in the opposite direction to the naively expected one as in $^3$He-A phase due to contributions from "unpaired electrons". Consequently, the domain wall current flows in the same direction with that of surface currents when the magnetic domain wall lies parallel to the sample surface, and therefore they contribute to the net current along the whole sample. We find that, due to the non-cancellation between the domain wall current and surface current, a Fulde-Ferrell-like superconducting state can be stabilized in an anisotropic sample for all the temperatures below the superconducting transition temperature.