Electric Field Induced Kondo Tunneling Through Double Quantum Dot

The effective spin Hamiltonian of a triple quantum dot with odd electron occupation weakly connected in series with left ($l$) and right ($r$) metal leads is composed of two-channel exchange and co-tunneling terms. Renormalization group equations for the corresponding three exchange constants $J_{l}$, $J_{r}$ and $J_{lr}$ are solved (to third order). Since $J_{lr}$ is relevant, the system is mapped on an anisotropic two-channel Kondo problem. The structure of the conductance ...

Resonant tunnelling through an Anderson impurity is investigated by employing a new perturbation scheme at nonequilibrium. This new approach gives the correct weak and strong coupling limit in $U$ by introducing adjustable parameters in the self-energy and imposing self-consistency of the occupation number of the impurity. We have found that the zero-temperature linear response conductance agrees well with that obtained from the exact sum rule. At finite temperature the condu...

We study the zero-bias conductance through the system of two quantum dots, one of which is embedded directly between the source and drain electrodes, while the second dot is side-coupled to the first one through a tunneling junction. Modeling the system using the two-impurity Anderson model, we compute the temperature-dependence of the conductance in various parameter regimes using the numerical renormalization group. We consider the non-interacting case, where we study the e...

Electron transport through parallel double quantum dot system with interdot tunneling and strong on-site Coulomb interaction is studied in the Kondo regime by using the finite-$U$ slave boson technique. For a system of quantum dots with degenerate energy levels, the linear conductance reaches the unitary limit ($2e^2/h$) due to the Kondo effect at low temperature when the interdot tunneling is absent. As the interdot tunneling amplitude increases, the conductance decreases in...

We construct a theoretical model to study the orbital Kondo effect in a parallel double quantum dot (DQD). Recently, pseudospin-resolved transport spectroscopy of the orbital Kondo effect in a DQD has been experimentally reported. The experiment revealed that when interdot tunneling is ignored, there exist two and one Kondo peaks in the conductance-bias curve for the pseudospin-non-resolved and pseudospin-resolved cases, respectively. Our theoretical studies reproduce this ex...

We employ the time-dependent non-crossing approximation to study the time averaged conductance for a single electron transistor in the Kondo regime when the dot level is sinusoidally driven from its equilibrium position by means of a gate voltage in finite bias. We find that the average conductance exhibits significant deviation from the monotonous reduction when the applied bias is equal to the driving frequency of the dot level. We investigate the effect of the temperature ...

We apply the functional renormalization group (FRG) method to calculate the conductance of a quantum dot in the Kondo regime. Starting from the exact FRG equations in Keldysh formulation for the Kondo exchange Hamiltonian in pseudo-fermion (pf) representation, we solve the coupled equations for the pf self energy and the coupling function, neglecting three-particle and higher correlation functions. The conductance $G$ as a function of temperature $T$ and bias voltage $V$ is c...

We report our study of the I-V curves in the transport through the quantum dot when an additional quantum dot lying in the Kondo regime is side-connected to it. Due to the Kondo scattering off the effective spin on a side-connected quantum dot the conductance is suppressed at low temperatures and at low source-drain bias voltages. This zero-bias anomaly is understood as enhanced Kondo scattering with decreasing temperature.

We study the competition between the Kondo effect and the exchange interaction in the parallel double quantum dot(DQDs) system within an effective action field theory. The strong on-site Coulomb interactions in DQDs are treated by using the Hubbard-Stratonovich transformation and the introduction of scalar potential fields. We show that a self-consistent perturbation approach, which takes into account the statistical properties of the potential fields acting on the electrons ...

We study the electronic transport in a double quantum dot structure connected to leads in the Kondo regime for both series and parallel arrangements. By applying a finite-U slave boson technique in the mean field approximation we explore the effect of level degeneracy in the conductance through the system. Our results show that for the series connection, as the energy difference of the localized dot levels increases, the tunneling via the Kondo state is destroyed. For the par...