Cooper pairing and BCS-BEC evolution in mixed-dimensional Fermi gases

Abstract

Similar to what has recently been achieved with Bose-Bose mixtures [Lamporesi et al., Phys. Rev. Lett. 104, 153202 (2010)], mixed-dimensional Fermi-Fermi mixtures can be created by applying a species-selective one-dimensional optical lattice to a two-species Fermi gas ($\sigma \equiv \{\uparrow ,\downarrow \}$), such a way that only one of the species feel the lattice potential and is confined to a quasi-two-dimensional geometry, while having negligible effect on the other, that is leaving it three dimensional. We investigate the ground state phase diagram of superfluidity for such mixtures in the BCS-BEC evolution, and find normal, gapped superfluid, gapless superfluid, and phase separated regions. In particular, we find a stable gapless superfluid phase where the unpaired $\uparrow$ and $\downarrow$ fermions coexist with the paired (or superfluid) ones in different momentum space regions. This phase is in some ways similar to the Sarma state found in mixtures with unequal densities, but in our case, the gapless superfluid phase is unpolarized and most importantly it is stable against phase separation.

8 pages with 4 figures

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Cited by in corpus (12)

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• A mixed dimensional Bose polaron
• $SU(3)$ Topological Insulators in the Honeycomb Lattice
• Topological transitions of gapless paired states in mixed-geometry lattices
• BCS-BEC Crossover in Mix-dimensional Fermi Gases
• Exotic superfluidity and pairing phenomena in atomic Fermi gases in mixed dimensions
• Ultra high temperature superfluidity in ultracold atomic Fermi gases with mixed dimensionality
• Anomalous Quasiparticle Reflection from the Surface of a ${}^3$He-${}^4$He Dilute Solution
• Effect of mediated interactions on a Hubbard chain in mixed-dimensional fermionic cold atoms