Abstract
We study the superfluid properties of short-coherence-length superconductorsdescribed by the extended Hubbard model with on-site repulsive and intersiteattractive interaction. We have analysed the superfluid stiffness and thermodynamicproperties of the model versus electron concentration and pairing interaction on atwo-dimensional square lattice with nearest- and next-nearest-neighbour hopping. Theeffects of phase fluctuations on anisotropic superconductivity of extended s-and dx2 −y2-wavetype were examined within the Kosterlitz–Thouless (KT) scenario. The KTcritical temperatures were determined and compared with those fromthe BCS–Hartree–Fock approximation. The Uemura-type plots, i.e.the critical temperature versus zero-temperature phase stiffness, wereobtained for both extended s- and d-wave pairings. The states with mixed(s∗ and dx2 −y2)symmetry, and in particular the time-reversal breaking state of s + id symmetry, wereanalysed and the phase diagrams taking into account these states are presented. Wealso briefly discuss the crossover from BCS to local pair superconductivity for the dx2 −y2-wavepairing. A comparison of the theoretical results with the experimental data, in particular thoseof Tc versusλ−2 (0),for high-Tccuprate superconductors is made.
Published Version
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