Fano-effect and negative differential conductance in asymmetric parallel coupled quantum dots

Transport through coupled quantum dot system has been studied, using non-equilibrium Green function formalism. Inter-dot tunneling with on-dot Coulomb repulsion is included while inter-dot Coulomb interaction is neglected. Behavior of system in transition from series configuration to symmetric parallel and in T-shaped coupled quantum dot system has been explored. Transmission coefficient as a function of Fermi energy shows Fano effect during transition. The system shows negative differential conductance and reverse current at low bias in series. It has been shown that the existence of negative differential conductance during transition from series to asymmetric parallel configuration is regulated by a competition between inter-dot tunneling and dot-lead coupling. Effect of inter-dot tunneling on negative differential conductance and on transport properties of T-shaped double dot has been studied.