Superfluid density at finite temperatures in two-dimensional attractive Hubbard model: crossover from BCS to Bose-Einstein condensation region

摘要

Effects of two corrections to the vertex part of the current-current correlation function for the two-dimensional attractive Hubbard model are examined to see the change of the stiffness or superfluid density N-s at temperature T-KT, whose dependence on the strength of the interaction displays crossover from BCS to Bose-Einstein condensation. The ladder correction gives no new transverse part, so it does not change N-s from non-gauge invariant calculation. On the contrary, the Aslamazov-Larkin-type correction gives rise to an additional term to the transverse part, improving our previous work on T-KT-U relation especially in the region of Bose-Einstein condensation. (C) 2000 Elsevier Science B.V. All rights reserved. [References: 9]