Abstract
We study the I-V characteristic 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 values U 0 and associated capacitances of the QD the effect on the I-V characteristic. Also the influence of the coupling constants on the I-V characteristic is investigated. Our approach puts forward a novel interpretation of experiments in the strong Coulomb regime.
Highlights
The overall shape of the I-V characteristic of a variety of systems in the nanometer scale sandwiched between metallic or superconductors leads has been recently a matter of study
We put the charge before biasing N0 = 0, such that Coulomb repulsion with the quantum dot (QD)-energy level is absent
We have studied the single particle current through a quantum dot coupled with two superconductor leads via a coupled Poisson Nonequilibrium Green function (PNEGF) formalism
Summary
The overall shape of the I-V characteristic of a variety of systems (metals, semiconductors, and molecular conductors) in the nanometer scale sandwiched between metallic or superconductors leads has been recently a matter of study (see [1, 2] and references therein). To this respect, pioneering work is done by Meir et al [33, 34] for N/QD/N systems, considering the interatomic Coulomb term Un↑n↓ as a measure of the charging energy e2/C Their purpose was to find the main object of the non-equilibrium formalism, namely, the QD Green-Keldysh function, in which the influence of the leads on the QD is taken into account. Coulomb repulsion is introduced via a self-consistent field (SCF) that depends dynamically on the applied bias (HQD + USCF) and, in consequence, on the actual number of electrons in the QD This approach constitutes the coupled Poisson NEGF formalism that has been discussed in the context of molecular conductors by Datta et al [4, 24].
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