title: Phase fluctuations in strongly coupled d-wave superconductors.
abstract: We present a numerically exact solution for the BCS Hamiltonian at any temperature, including the degrees of freedom associated with classical phase, as well as amplitude fluctuations via a Monte Carlo integration. This allows for an investigation over the whole range of couplings: from weak attraction, as in the well-known BCS limit, to the mainly unexplored strong-coupling regime of pronounced phase fluctuations. In the latter, two characteristic temperatures T(*) and T(c), associated with short- and long-range ordering, respectively, can be identified in a mean-field-motivated Hamiltonian. T(*) at the same time corresponds to the opening of a gap in the excitation spectrum. In addition to introducing a novel procedure to study strongly coupled d-wave superconductors, our results indicate that classical phase fluctuations are not sufficient to explain the pseudogap features of high-temperature superconductors.
authors.affiliation: Max-Planck-Institut für Festkörperforschung, 70569 Stuttgart, Germany.
authors.forename: Matthias
authors.initials: M
authors.lastname: Mayr
authors.forename: Gonzalo
authors.initials: G
authors.lastname: Alvarez
authors.forename: Cengiz
authors.initials: C
authors.lastname: Sen
authors.forename: Elbio
authors.initials: E
authors.lastname: Dagotto