• DOI:10.1103/PHYSREVB.103.024521
• Corpus ID: 226254281

Distortional weak-coupling instability of Bogoliubov Fermi surfaces

@article{Timm2020DistortionalWI,
  title={Distortional weak-coupling instability of Bogoliubov Fermi surfaces},
  author={Carsten Timm and P. M. R. Brydon and Daniel Agterberg},
  journal={Physical Review B},
  year={2020},
  volume={103},
  pages={024521}
}

• C. Timm, P. Brydon, D. Agterberg
• Published 5 November 2020
• Physics
• Physical Review B

Centrosymmetric multiband superconductors which break time-reversal symmetry generically have two-dimensional nodes, i.e., Fermi surfaces of Bogoliubov quasiparticles. We show that the coupling of the electrons to the lattice always leads to a weak-coupling instability of such a state toward spontaneous breaking of inversion symmetry at low temperatures. This instability is driven by a Cooper logarithm in the internal energy but the order parameter is not superconducting but distortional. We present a comprehensive symmetry analysis and introduce a measure that allows us to compare the strengths of competing distortional instabilities. Moreover, we discuss the instability using an effective single-band model. This framework reveals a duality mapping of the effective model which maps the distortional order parameter onto a superconducting one, providing a natural explanation for the Cooper logarithm and the weak-coupling nature of the instability. Finally, we consider the possibility of a pair-density wave state when inversion symmetry is broken. We find that it can indeed exist but does not affect the instability itself.