Density-matrix functionals for pairing in mesoscopic superconductors

TL;DR

This paper introduces a density-matrix functional theory for pairing in mesoscopic superconductors, improving upon BCS by explicitly conserving particle number and accurately reproducing pairing energies across various conditions.

Contribution

It develops a novel functional based on occupation numbers that generalizes BCS and incorporates particle number conservation corrections.

Findings

Perfect reproduction of pairing energies for any particle number and coupling

Functional accurately benchmarks against the pairing Hamiltonian

Generalizes BCS approach for mesoscopic systems

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.