Pairing properties of cold fermions in a honeycomb lattice

Abstract

The pairing properties of ultracold fermions, with an attractive interaction, loaded in a honeycomb (graphene-like) optical lattice are studied in a mean-field approach. We emphasize, in the presence of a harmonic trap, the unambiguous signatures of the band structure around half-filling (i.e. the conical intersections) in the local order parameter, in particular in the situations of either imbalanced hopping parameters or imbalanced populations. It can also be observed in the system response to external perturbation, for instance by measuring the pair destruction rate when modulating the optical lattice depth. Going beyond the mean-field level, we estimate the critical temperature for the "condensation" of the preformed pairs. © 2012 Europhysics Letters Association.