title: Broadening of the derivative discontinuity in density functional theory.
abstract: We clarify an important aspect of density functional theories, the broadening of the derivative discontinuity (DD) in a quantum system, with fluctuating particle number. Our focus is on a correlated model system, the single level quantum dot in the regime of the Coulomb blockade. We find that the DD-broadening is controlled by the small parameter Γ/U, where Γ is the level broadening due to contacting and U is a measure of the charging energy. Our analysis suggests that Kondoesque fluctuations have a tendency to increase the DD-broadening in our model by a factor of two.
authors.affiliation: Institute of Nanotechnology, Karlsruhe Institute of Technology, D-76021 Karlsruhe, Germany.
authors.forename: F
authors.initials: F
authors.lastname: Evers
authors.forename: P
authors.initials: P
authors.lastname: Schmitteckert