Michele Pini (Institute of Physics, University of Augsburg)

Unconventional Instabilities in Fermionic Matter: Cavity‑Mediated Phases in Fermi Gases and Non‑Thermal Pairing in Superconductors

In this talk, I will present two recent works [1,2] that explore how engineered interactions give rise to unconventional pairing phenomena in fermionic systems. I will first show how a single-wave-vector cavity field induces long-range, spatially modulated interactions in an ultracold Fermi gas, giving rise to a reshaped Fermi surface and unconventional superfluid phases featuring Cooper pairs with both zero and finite center-of-mass momentum. I will then turn to superconductors, presenting a genuinely non-thermal mechanism that can enhance electron pairing in non-equilibrium steady states. Using a non-equilibrium extension of Eliashberg theory, I will show how this non-thermal "pairing glue" is active even in the weak-coupling regime and discuss two setups where it could potentially be realized.

[1] B. Frank, Mi. Pini, H. Lang, F. Piazza, The fate of the Fermi surface coupled to a single-wave-vector cavity mode, arXiv:2505.11452.
[2] M. Pini, C.H. Johansen, F. Piazza, Non-thermal pairing glue of electrons in the steady state, arXiv:2512.13065.