Eur. Phys. J. B 53, 417-432 (2006)
https://doi.org/10.1140/epjb/e2006-00397-0

Internal structure of fluctuating Cooper pairs

¹ Institut de Physique, Université de Neuchâtel, 2000 Neuchâtel, Switzerland
² Dipartimento di Fisica, Universitá degli Studi di Salerno, 84084 Baronissi, Italy
³ School of Engineering, Swiss Federal Institute of Technology (EPFL), 1015 Ecublens, Switzerland

Corresponding author: ^a massimiliano.capezzali@epfl.ch

Received: 10 January 2006
Revised: 12 September 2006
Published online: 1 November 2006

Abstract

In order to obtain information about the internal structure of fluctuating Cooper pairs in the pseudogap state and below the transition temperature of high T_c superconductors, we solve the Bethe-Salpeter equation for the two-electron propagator in order to calculate a “pair structure function” that depends on the internal distance between the partners and on the center of mass momentum P of the pair. We use an attractive Hubbard model with a local potential for s-wave and a separable potential for d-wave symmetry. The amplitude of g_P for small ρ depends on temperature, chemical potential and interaction symmetry, but the ρ dependence itself is rather insensitive to the interaction strength. Asymptotically g_P decreases as an inverse power of ρ for weak coupling, but exponentially when a pseudogap develops for stronger interaction. Some possibilities of observing the pair structure experimentally are mentioned.