Critical temperature for the two-dimensional attractive Hubbard model

Abstract

The critical temperature for the attractive Hubbard model on a square lattice is determined from the analysis of two independent quantities, the helicity modulus ${\ensuremath{\rho}}_{s}$ and the pairing correlation function ${P}_{s}.$ These quantities have been calculated through quantum Monte Carlo simulations for lattices up to $18\ifmmode\times\else\texttimes\fi{}18,$ and for several densities, in the intermediate-coupling regime. Imposing the universal-jump condition for an accurately calculated ${\ensuremath{\rho}}_{s},$ together with thorough finite-size scaling analyses (in the spirit of the phenomenological renormalization group) of ${P}_{s},$ suggests that ${T}_{c}$ is considerably higher than hitherto assumed.