Two-dimensional fermionic superfluids, pairing instability and vortex liquids in the absence of time reversal symmetry

Abstract

We consider a generic two-dimensional system of fermionic particles with attractive interactions and no disorder. If time-reversal symmetry is absent, it is possible to obtain incompressible insulating states in addition to the superfluid at zero temperature. The superfluid-insulator phase transition is found to be second order in type-II systems using a perturbative analysis of Cooper pairing instability in quantum Hall states of unpaired fermions. We obtain the pairing phase diagram as a function of chemical potential (density) and temperature. However, a more careful analysis presented here reveals that the pairing quantum phase transition is always preempted by another transition into a strongly correlated normal state which retains Cooper pairing and cannot be smoothly connected to the quantum Hall state of unpaired fermions. Such a normal phase can be qualitatively viewed as a liquid of vortices, although it may acquire conventional broken symmetries. Even if it did not survive at finite temperatures its influence would be felt through strong quantum fluctuations below a crossover temperature scale. These conclusions directly apply to fermionic ultra-cold atom systems near unitarity, but are likely relevant for the properties of other strongly correlated superfluids as well, including high temperature superconductors.

11 pages, 3 figures, published version

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Cited by in corpus (7)

• Two-dimensional heavy fermions on the strongly correlated boundaries of Kondo topological insulators
• Fractional topological insulators of Cooper pairs induced by proximity effect
• s-wave Cooper pair insulators and theory of correlated superconductors
• Vortices and vortex states in Rashba spin-orbit-coupled condensates
• Interaction proximity effect at the interface between a superconductor and a topological insulator quantum well
• Vortex states in a non-Abelian magnetic field
• The phase diagram of two-dimensional fast-rotating ultra-cold fermionic atoms near unitarity