Berlin 2024 – wissenschaftliches Programm
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TT: Fachverband Tiefe Temperaturen
TT 36: Superconductivity: Theory I
TT 36.3: Vortrag
Mittwoch, 20. März 2024, 10:00–10:15, H 3005
Stability of Bogoliubov Fermi Surfaces within BCS Theory — Ankita Bhattacharya1,2 and •Carsten Timm2 — 1Department of Physics and Astronomy, Uppsala University, Box 516, 75120 Uppsala, Sweden — 2Institute of Theoretical Physics, TU Dresden, 01062 Dresden, Germany
It has recently been realized that the gap nodes of multiband superconductors that break time-reversal symmetry generically take the form of Fermi surfaces of Bogoliubov quasiparticles. These Fermi surfaces lead to a nonzero density of states (DOS) at the Fermi energy, which typically disfavors such superconducting states. It has thus not been clear whether these states can be stable for reasonable pairing interactions or are preempted by time-reversal-symmetric states with vanishing DOS. Applying BCS theory to a paradigmatic model, we show that the time-reversal-symmetry-breaking states are indeed stabilized over broad parameter ranges at weak coupling [1]. Moreover, we introduce a fast method that involves solving the inverse BCS gap equation, does not require iteration, does not suffer from convergence problems, and can handle metastable solutions.
[1] A. Bhattacharya, C. Timm, Phys. Rev. B 107 (2023) L220501