Bogoliubov Fermi surfaces stabilized by spin-orbit coupling

TL;DR

This paper demonstrates that Bogoliubov Fermi surfaces in multiband superconductors can be thermodynamically stable due to spin-orbit coupling, with implications for experimental detection and phase transition behavior.

Contribution

It provides a mean-field phase diagram showing the stability of Bogoliubov Fermi surfaces influenced by spin-orbit coupling and anisotropy effects.

Findings

Bogoliubov Fermi surfaces can be stabilized at moderate spin-orbit coupling.

First-order phase transition driven by intra- and interband pairing competition.

Experimental signatures include residual density of states and magnetic order.

Abstract

It was recently understood that centrosymmetric multiband superconductors that break time-reversal symmetry generically show Fermi surfaces of Bogoliubov quasiparticles. We investigate the thermodynamic stability of these Bogoliubov Fermi surfaces in a paradigmatic model. To that end, we construct the mean-field phase diagram as a function of spin-orbit coupling and temperature. It confirms the prediction that a pairing state with Bogoliubov Fermi surfaces can be stabilized at moderate spin-orbit coupling strengths. The multiband nature of the model also gives rise to a first-order phase transition, which can be explained by the competition of intra- and interband pairing and is strongly affected by cubic anisotropy. For the state with Bogoliubov Fermi surfaces, we also discuss experimental signatures in terms of the residual density of states and the induced magnetic order. Our results show that Bogoliubov Fermi surfaces of experimentally relevant size can be thermodynamically stable.