Bogoliubov-Fermi Surfaces in Noncentrosymmetric Multicomponent Superconductors

TL;DR

This paper demonstrates that in noncentrosymmetric multicomponent superconductors with broken time reversal symmetry, stable Bogoliubov-Fermi surfaces can form, which may vanish at higher order parameters through a Lifshitz transition, affecting the quasiparticle spectrum.

Contribution

It reveals the conditions under which Bogoliubov-Fermi surfaces are stable in noncentrosymmetric superconductors with broken time reversal symmetry, and describes their evolution with increasing order parameter.

Findings

Bogoliubov-Fermi surfaces are stable due to lack of inversion symmetry.

These surfaces can disappear via a Lifshitz transition at higher order parameters.

The effective Hamiltonian near the Fermi surface explains the quasiparticle spectrum.

Abstract

We show that when the time reversal symmetry is broken in a multicomponent superconducting condensate without inversion symmetry the resulting Bogoliubov quasiparticles generically exhibit mini-Bogoliubov-Fermi (BF) surfaces, for small superconducting order parameter. The absence of inversion symmetry makes the BF surfaces stable with respect to weak perturbations. With sufficient increase of the order parameter, however, the Bogoliubov-Fermi surface may disappear through a Lifshitz transition, and the spectrum this way become fully gapped. Our demonstration is based on the computation of the effective Hamiltonian for the bands near the normal Fermi surface by the integration over high-energy states. Exceptions to the rule, and experimental consequences are briefly discussed.