Single Charge Current in a Normal Mesoscopic Region Attached to Superconductor Leads via a Coupled Poisson Nonequilibrium Green Function Formalism

Abstract

We study theI-Vcharacteristic of mesoscopic systems or quantum dot (QD) attached to a pair of superconducting leads. Interaction effects in the QD are considered through the charging energy of the QD; that is, the treatment of current transport under a voltage bias is performed within a coupled Poisson nonequilibrium Green function (PNEGF) formalism. We derive the expression for the current in full generality but consider only the regime where transport occurs only via a single particle current. We show for this case and for various charging energies valuesU0and associated capacitances of the QD the effect on theI-Vcharacteristic. Also the influence of the coupling constants on theI-Vcharacteristic is investigated. Our approach puts forward a novel interpretation of experiments in the strong Coulomb regime.