Multiband superfluidity and superfluid to band-insulator transition of strongly interacting fermions in an optical lattice

Abstract

We study the multiband superfluid and the superfluid (SF) to band insulator (BI) transition of strongly interacting fermionic atoms in an optical lattice at a filling of two fermions per well. We present physical arguments to show that a consistent mean field description of this problem is obtained by retaining only intraband pairing between the fermions. Using this approach we obtain a reasonable account of the experimentally observed critical lattice depth for the SF-BI transition and the modulated components of the condensate density, and make predictions for the lattice depth dependence of the quasiparticle gap which can be tested in future experiments. We also highlight some interesting features unique to cold atom superfluids within this intraband pairing approximation; for instance, the pair field is forced to be uniform in space and the Hartree field vanishes identically. These arise as a result of the fact that while the pairing interaction is cut off at the scale of the Debye frequency in conventional superconductors, or at the lattice scale in tight binding model Hamiltonians, such a cutoff is absent for cold Fermi gases.

5 pages, 2 figures

References in corpus (15)

• Observation of the Pairing Gap in a Strongly Interacting Fermi Gas
• Molecular Probe of Pairing in the BEC-BCS Crossover
• Evidence for Superfluidity of Ultracold Fermions in an Optical Lattice
• Thermodynamics of the BCS-BEC crossover
• Direct Observation of the Superfluid Phase Transition in Ultracold Fermi Gases
• Quantum Fluctuations in the Superfluid State of the BCS-BEC Crossover
• Epsilon expansion for a Fermi gas at infinite scattering length
• Renormalization group fixed points, universal phase diagram, and 1/N expansion for quantum liquids with interactions near the unitarity limit
• Equation of state of a superfluid Fermi gas in the BCS-BEC crossover
• BCS-BEC crossover on the two-dimensional honeycomb lattice
• Large-N expansion for unitary superfluid Fermi gases
• Superfluid-Insulator Transition of Strongly Interacting Fermi Gases in Optical Lattices
• Superfluid-insulator transitions of the Fermi gas with near-unitary interactions in a periodic potential
• Stability of Superflow for Ultracold Fermions in Optical Lattices
• Multiband-Driven Superfluid-Insulator Transition of Fermionic Atoms in Optical Lattices: A Dynamical Mean-Field-Theory Study

Cited by in corpus (9)

• Fermi-Hubbard physics with atoms in an optical lattice
• Collective modes and superflow instabilities of strongly correlated Fermi superfluids
• Reentrant BCS-BEC crossover and a superfluid-insulator transition in optical lattices
• Finite Momentum Pairing Instability of Band-Insulators With Multiple Bands
• Fermionic Superfluid from a Bilayer Band Insulator in an Optical Lattice
• Unitarity in periodic potentials: a renormalization group analysis
• Superfluidity of Dirac Fermions in a Tunable Honeycomb Lattice: Cooper Pairing, Collective Modes, and Critical Currents
• Transition from Band insulator to Bose-Einstein Condensate superfluid and Mott State of Cold Fermi Gases with Multiband Effects in Optical Lattices
• The phase diagram of two-dimensional fast-rotating ultra-cold fermionic atoms near unitarity