Aharonov-Bohm flux control of transport and microwave energy absorption in a parallel double-dot system

We analyze a tunnel-coupled double-dot structure in a parallel arrangement between leads in the presence of magnetic flux to determine its charge transport and microwave absorption properties. Nonequilibrium. Green´s function methods are employed (taking account of dot-lead tunnel coupling, electron-phonon interaction and inter-dot Coulomb repulsion) to calculate the energies, populations and linewidths of the bonding and antibonding states in the double-dot structure for various values of magnetic flux threading the structure. We find that there are resonant values of the Aharonov-Bohm magnetic flux, for which one of these states is disconnected from the leads by phase and there is only one step in the current-voltage characteristics. For non-resonant fluxes there are either two steps or one sharp step depending on the common equilibrium chemical potential of the leads. In the case of two steps, the current value in the plateau region between the steps is an oscillatory function of the applied magnetic flux. In the present work, we also analyze microwave energy absorption. At a resonant flux, when one of levels is disconnected, there is residual absorption of the external microwave energy even at high applied bias.