Resonant Tunneling throughQuantumDots

Motivated by recent experiments we analyse a new setup of capacitively coupled semiconductor quantum dots. We identify a region where Kondo-assisted tunneling should be observable. We nd an eeective mapping to a single quantum dot with controllable multi-level structure. We study electron transport through strongly coupled quantum dots in the presence of strong Coulomb repulsion and coupling to metallic leads. This work is motivated by recent experiments on semiconductor quantum dots displaying Kondo-type resonances in conductancee1]. Previous theoretical work has mainly concentrated on single quantum dots, with one spin-degenerate level, possibly exposed to nite electric and magnetic eldss2,3]. Some work has also been done on the case of more than one level or orbital state in the dot 4,5] as well as on double quantum dots 4,6]. Here we study a system of two capacitively coupled quantum dots in parallel, a connguration recently suggested and experimentally studied at the MPI in Stuttgart 7]. For large level spacing, only one spin-degenerate level will be relevant in each dot. Including the electron-electron interaction via the standard Coulomb blockade model, we take the following model P kri kri a y kri a kri describes the left and right reservoirs (r=L,R) coupled to the upper or lower quantum dot (i=1,2), where ="; # is the spin and k labels the states. H D = P i i c y i c i + V N1N2 describes the two quantum dots which are only coupled by the electrostatic energy V. The latter is a quadratic form in the charges Q i = eN i of the two dots and involves the various capacitances between the dots and the reservoirs as well as all voltages applied to the system. Finally, the coupling to the reservoirs is described by the standard tunneling Hamiltonian H T = P kri (T ri k a y kri c i + h:c:). Since there is no direct tunneling coupling between the two dots, we see that the system is eeectively identical to a single dot with two spin-degenerate states labelled by i = 1; 2. The eeective single-particle energies are