Density-matrix functionals for pairing in mesoscopic superconductors

Abstract

A functional theory based on single-particle occupation numbers is developed for pairing. This functional, that generalizes the BCS approach, directly incorporates corrections due to particle number conservation. The functional is benchmarked with the pairing Hamiltonian and reproduces perfectly the energy for any particle number and coupling.

Comments: 4 pages, 4 figures, revised version