Nematic Bogoliubov Fermi surfaces from magnetic toroidal order in FeSe$_{1-x}$S$_x$

TL;DR

This paper proposes that magnetic toroidal order causes Bogoliubov Fermi surfaces and nematic behavior in FeSe$_{1-x}$S$_x$, linking broken time-reversal symmetry with specific magnetic and superconducting orders.

Contribution

It introduces a symmetry-based analysis connecting magnetic toroidal order to Bogoliubov Fermi surfaces and nematicity in FeSe$_{1-x}$S$_x$, and discusses their origins and effects.

Findings

Magnetic toroidal order likely causes time-reversal symmetry breaking.

Supercurrents can induce Ne9el magnetic order in Fe-based superconductors.

Bogoliubov Fermi surfaces are associated with nematic behavior in the studied material.

Abstract

Recently it has been argued that the superconducting state of FeSe$_{1-x}$S$_x$ exhibits Bogoliubov Fermi surfaces for $x>0.17$. These Bogoliubov Fermi surfaces appear together with broken time-reversal symmetry and surprisingly demonstrate nematic behavior in a structurally tetragonal phase. Through a symmetry-based analysis of Bogoliubov Fermi surfaces that can arise from broken time-reversal symmetry, we argue that the likely origin of time-reversal symmetry breaking is due to magnetic toroidal order. We show that this magnetic toroidal order naturally appears as a consequence of either static N\'{e}el antiferromagnetic order or due to the formation of a spontaneous pair density wave superconducting order. Finally, we reveal that independent of the presence of Bogoliubov Fermi surfaces, supercurrents will induce N\'{e}el magnetic order in many Fe-based superconductors.