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Fate of the Fermi Surface Coupled to a Single-Wave-Vector Cavity Mode
Bernhard Frank1, Michele Pini2,3, Johannes Lang4
1Technische Universität Dresden, Institut für Theoretische Physik and Würzburg-Dresden Cluster of Excellence ct.qmat, 01062 Dresden, Germany.
Physical Review Letters
|April 25, 2026
Summary
We solved competing instabilities in ultracold Fermi gases induced by electromagnetic fields. Repulsive interactions lead to novel superfluid phases, unlike attractive interactions which favor density-wave instability.
Area of Science:
- Atomic, Molecular, and Optical Physics
- Condensed Matter Physics
- Quantum Gases
Background:
- Electromagnetic fields in cavities create unique interactions in ultracold Fermi gases.
- Previous studies focused only on attractive interactions, leaving repulsive regimes unexplored.
Purpose of the Study:
- To fully solve competing instabilities of the Fermi surface induced by single-wavelength interactions.
- To investigate phenomena in both attractive and repulsive interaction regimes.
Main Methods:
- Theoretical analysis of Fermi surface instabilities.
- Solving for competing instabilities in a single-wavelength interaction model.
Main Results:
- Density-wave instability dominates for attractive interactions.
- Repulsive interactions lead to nonsuperradiant superfluid phases with fermion pairs forming at various momenta.
- Anisotropic deformation of the Fermi surface occurs even without symmetry-breaking instabilities.
Conclusions:
- The study provides a complete solution for Fermi surface instabilities in this unique system.
- Predicted phenomena are experimentally accessible with current technology.
- Highlights novel superfluid phases driven by repulsive interactions.
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