Electron transport through a biased asymmetric double-dot system in a parallel arrangement between leads

Abstract

We examine the transport properties of a tunnel-coupled asymmetric double-dot structure in a parallel arrangement between leads in the presence of Aharonov-Bohm magnetic flux and an additional bias voltage applied between the dots. We solve the Schrodinger equation for the energy eigenfunctions and eigenvalues of a biased asymmetric double-dot system. The magnetic flux-induced Peierls phase factors experienced by electrons in tunneling from/to the leads to/from double-dot levels are determined and incorporated. Employing the nonequilibrium Green's function formalism we calculate the lead-to-lead current, taking account of dot-lead tunnel coupling and Coulomb repulsion. We demonstrate that, for appropriate parameter values (such as lead-to-lead bias voltage and equilibrium chemical potential of the leads), the lead-to-lead current oscillates as a function of applied magnetic field, if the dot-to-dot bias compensates the structure asymmetry and only one of the double-dot levels is conductive. We also show that when both levels become conductive, their interference is destructive and the total lead-to-lead current decreases with increasing magnetic field. This decrease is larger for larger dots.