Ultra-cold fermions in real or fictitious magnetic fields: The BCS-BEC evolution and the type-I--type-II transition

Abstract

We study ultra-cold neutral fermion superfluids in the presence of fictitious magnetic fields, as well as charged fermion superfluids in the presence of real magnetic fields. Charged fermion superfluids undergo a phase transition from type-I to type-II superfluidity, where the magnetic properties of the superfluid change from being a perfect diamagnet without vortices to a partial diamagnet with the emergence of the Abrikosov vortex lattice. The transition from type-I to type-II superfluidity is tunned by changing the scattering parameter (interaction) for fixed density. We also find that neutral fermion superfluids such as ${}^6$Li and ${}^{40}$K are extreme type-II superfluids, and that they are more robust to the penetration of a fictitious magnetic field in the BCS-BEC crossover region near unitarity, where the critical fictitious magnetic field reaches a maximum as a function of the scattering parameter (interaction).

4+ pages with 2 figures

References in corpus (3)

• Synthetic magnetic fields for ultracold neutral atoms
• Vortices and Superfluidity in a Strongly Interacting Fermi Gas
• Raman processes and effective gauge potentials

Cited by in corpus (4)

• Evolution from BCS to BEC superfluidity in the presence of spin-orbit coupling
• Extracting quantum-geometric effects from Ginzburg-Landau theory in a multiband Hubbard model
• Dynamical Phase Diagram of Ultracold Josephson Junctions
• Bypassing the lattice BCS-BEC crossover in strongly correlated superconductors: resilient coherence from multiorbital physics