Eur. Phys. J. B 81, 95-102 (2011)
https://doi.org/10.1140/epjb/e2011-10907-6

Participation ratio and fidelity analyses as tools to study BCS-BEC crossover

¹ Department of Physics, Indian Institute of Technology Guwahati, Guwahati, 781039 Assam, India
² Research Center for Dielectric and Advanced Matter Physics, Pusan National University, 609-735 Busan, South Korea

Corresponding author: ^a poulumi@iitg.ernet.in

Received: 22 November 2010
Revised: 3 March 2011
Published online: 13 April 2011

Abstract

Solving Bogoliubov-de Gennes (BdG) equations for a two dimensional Hubbard model with random on-site disorder, we compute the participation ratio and fidelity to establish conviction for a BCS-BEC crossover scenario at intermediate values of disorder proposed earlier [P. Dey, S. Basu, J. Phys.: Condens. Matter 20, 485205 (2008)]. The participation ratio analysis suggests the onset of a phase with shrunk pairs extending over moderate number of lattice sites, which however preserves the superfluid character. The fidelity or the ground state overlap for two different (but closely lying) values of the disorder strength shows an abrupt drop at the immediate neighbourhood of the disorder strength where an onset of a paired (bose-like) phase occurs.