SAMOP 2023 – scientific programme
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A: Fachverband Atomphysik
A 19: Ultra-cold Atoms, Ions and BEC III (joint session A/Q)
A 19.2: Talk
Wednesday, March 8, 2023, 14:45–15:00, F428
Competing non-superradiant Fermi-surface instabilities induced by cavity-mediated interactions — Bernhard Frank1, •Michele Pini2, and Francesco Piazza2 — 1Institut für Theoretische Physik and Würzburg-Dresden Cluster of Excellence ct.qmat, Technische Universität Dresden, 01062 Dresden, Germany — 2Max Planck Institute for the Physics of Complex Systems, Nöthnitzer Str. 38, 01187, Dresden, Germany
The experimental realization of ultracold Fermi gases in optical resonators provides an interesting new platform to study unconventional quantum phases of matter induced by long-range cavity-mediated interactions. So far, mostly superradiant instabilities accompanied by charge density waves of the fermions have been studied in these systems. Here, we report instead on pair condensation instabilities, solving the competition problem within a controlled perturbative approach by exploiting the long-range nature of the cavity-mediated interaction. We show that a spin-polarized Fermi gas undergoes a phase transition to either a Cooper or a pair density wave superfluid at a common Tc. Below Tc, however, these phases turn out to be mutually exclusive, with one of them always dominating above the other. Moreover, these pairing instabilities occur both for attractive or repulsive interactions. This allows to observe them in the latter regime, where the superradiant instability is absent. In addition, the value of Tc is also found to be well within reach of the parameters of current experimental realizations, which is very promising for an experimental observation of these non-superradiant instabilities in the near future.