BCS-BEC crossover on the two-dimensional honeycomb lattice
arXiv:cond-mat/0606470 · doi:10.1103/PhysRevLett.97.230404
Abstract
The attractive Hubbard model on the honeycomb lattice exhibits, at half-filling, a quantum critical point (QCP) between a semimetal with massless Dirac fermions and an s-wave superconductor (SC). We study the BCS-BEC crossover in this model away from half-filling at zero temperature and show that the appropriately defined crossover line (in the interaction-density plane) passes through the QCP at half-filling. For a range of densities around half-filling, the ``underlying Fermi surface'' of the SC, defined as the momentum space locus of minimum energy quasiparticle excitations, encloses an area which evolves nonmonotonically with interactions. We also study fluctuations in the SC and the semimetal, and show the emergence of an undamped Leggett mode deep in the SC. We consider possible implications for experiments on ultracold atoms and high temperature SCs.
Revised - added section on the Fermi surface evolution, corrected error in superfluid density, added possible implications for cuprates
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- Near zero modes in condensate phases of the Dirac theory on the honeycomb lattice
- Lattice with a Twist : Helical Waveguides for Ultracold Matter
- Collective modes and superflow instabilities of strongly correlated Fermi superfluids
- Magnetic field induced semimetal-to-canted-antiferromagnet transition on the honeycomb lattice
- Properties of A Class of Topological Phase Transition
- Nonequilibrium-induced metal-superconductor quantum phase transition in graphene
- Spatially-modulated Superfluid States in Fermionic Optical Ladder Systems with Repulsive Interactions