Eur. Phys. J. B 2, 509-523 (1998)
https://doi.org/10.1007/s100510050275

An investigation of the 2D attractive Hubbard model

¹ Service de Physique Théorique, CEA-Saclay, 91191 Gif-sur-Yvette Cedex, France
² ASCI, Btiment 506, Université Paris Sud, 91405 Orsay Cedex, France
³ Fakultät für Physik, Universität Bielefeld, Postfach 10 01 31, 33501 Bielefeld, Germany

Corresponding author: ^a lacaze@spht.saclay.cea.fr

Received: 30 October 1996
Revised: 23 October 1997
Accepted: 29 January 1998
Published online: 15 April 1998

Abstract

We present an investigation of the 2D attractive Hubbard model, considered as an effective model relevant to superconductivity in strongly interacting electron systems. We use both hybrid Monte-Carlo simulations and existing hopping parameter expansions to explore the low temperature domain. The increase of the static S-wave pair correlation with decreasing temperature, which depends weakly on the band filling in the explored temperature range, is analyzed in terms of an expected Kosterlitz-Thouless superconducting transition. Using both our data and previously published results, we show that the evidence for this transition is weak: If it exists, its temperature is very low. The number of unpaired electrons remains nearly constant with temperature at fixed attractive potential strength. In contrast, the static magnetic susceptibility decreases fast with temperature, and cannot be related only to pair formation. We introduce a method by which the Padé approximants of the existing series for the susceptibility give sensible results down to rather low temperature region, as shown by comparison with our numerical data.