N. S. Maslova

Localized charge bifurcation in the coupled quantum dots

Abstract We theoretically analyzed localized charge relaxation in a double quantum dot (QD) system coupled with continuous spectrum states in the presence of Coulomb interaction between electrons within a dot. We have found that for a wide range of the system parameters charge relaxation occurs through two stable regimes with significantly different relaxation rates. A certain instant of time exists in the system at which rapid switching between stable regimes takes place. We consider this phenomenon to be applicable for the creation of active elements in nano-electronics based on the fast transition effect between two stable states.

Charge and spin configurations in the coupled quantum dots with Coulomb correlations induced by tunneling current

We investigated the peculiarities of non-equilibrium charge states and spin configurations in the system of two strongly coupled quantum dots (QDs) weakly connected to the electrodes in the presence of Coulomb correlations. We analyzed the modification of non-equilibrium charge states and different spin configurations of the system in a wide range of applied bias voltage and revealed well pronounced ranges of system parameters where negative tunneling conductivity appears due to the Coulomb correlations.

Charge trapping in the system of interacting quantum dots

Abstract We analyzed the localized charge dynamics in the system of N interacting single-level quantum dots (QDs) coupled to the continuous spectrum states in the presence of Coulomb interaction between electrons within the dots. Different dots geometry and initial charge configurations were considered. The analysis was performed by means of Heisenberg equations for localized electron pair correlators. We revealed that charge trapping takes place for a wide range of system parameters and we suggested the QDs geometry for experimental observations of this phenomenon. We demonstrated significant suppression of Coulomb correlations with the increasing QDs number. We found the appearance of several time scales with the strongly different relaxation rates for a wide range of the Coulomb interaction values.

Control of the non-stationary spin-polarized tunneling currents by applied bias changing

Abstract We analyze time evolution of the opposite spin electron occupation for the single Anderson impurity coupled to two reservoirs in the presence of applied bias voltage. We demonstrate that non-stationary spin-polarized currents are flowing in the both leads. We reveal that spin polarization and direction of the non-stationary currents in each lead can be simultaneously inverted by the sudden changing of the applied bias voltage.

Kondo correlations formation and the local magnetic moment dynamics in the Anderson model

Abstract We investigated the typical time scales of the Kondo correlations formation for the single-state Anderson model, when coupling to the reservoir is switched on at the initial time moment. The influence of the Kondo effect appearance on the system non-stationary characteristics was analyzed and discussed.

On the density of states for the Hubbard model: pseudo-particle Keldysh diagram method - an alternative to DMFT?

It is shown how to construct Keldysh diagram technique for pseudo-particle approach to the Hubbard model. We propose self-consistent equations for pseudo particle and electron Green’s functions in Keldysh diagram technique. Nonlocal effects (spatial dispersion) are included in single impurity problem in this method. Thus we can get rid of the artificial central peak (of Kondo type) in the density of states which is inevitable in Dynamical Mean Field Theory (DMFT). The changes in the density of states for 2D Hubbard model due to variation of Coulomb repulsion U and electron concentration are analyzed.

Time evolution of an entangled initial state in coupled quantum dots with Coulomb correlations

We proved that for arbitrary mixed state the concurrence and the entanglement are determined by the average value of electron’s pair correlation functions particular combinations. We analyzed the dynamics of the initial two-electronic state in two interacting single-level quantum dots (QDs) with Coulomb correlations, weakly tunnel coupled with an electronic reservoir. We obtained correlation functions of all orders for electrons in the QDs by decoupling high-order correlations between localized and band electrons in the reservoir. Analysis of the pair correlation functions time evolution allows to follow the changes of the concurrence and the entanglement during the relaxation and transient processes. We investigated dependence of the concurrence on the value of Coulomb interaction and energy levels spacing and found its monotonic behavior. The most interesting physical effect is that more entangled state than the initial one can be formed during the charge relaxation due to the Coulomb correlations. We also demonstrated that behavior of the two-electronic entangled state pair correlation functions in coupled QDs points to the fulfillment of the Hund’s rule for the strong Coulomb interaction. We revealed the appearance of dynamical inverse occupation of the QDs energy levels during the relaxation processes. Our results open up further perspectives in solid state quantum information based on the controllable dynamics of the entangled electronic states.

Tunneling current emission spectrum of biased impurity in the presence of electron-phonon interaction

Theoretical analysis of the tunneling current noise spectra through the single-level impurity in the presence of electron-phonon interaction is performed by means of the non-equilibrium Green’s function formalism. A fundamental link between quantum noise in tunneling contact and light emission processes is revealed. Tunneling current noise spectra through a single level impurity atom is identified as a source of experimentally observed light emission from bias STM contacts.

Two-level quantum dot susceptibility and polarization in the presence of Coulomb correlations

Susceptibility and polarization of two-level quantum dot (QD) with Coulomb correlations between localized electrons weakly connected to the reservoirs were carefully analyzed. It was revealed that both susceptibility and polarization depend strongly on high-order correlation functions of localized in QD electrons. It was demonstrated that susceptibility and polarization can be controlled by changing of applied bias voltage value, Coulomb correlations strength and Rabi frequency.

Nonequilibrium diagram technique for tunneling problems in the effective mass approach

It is shown how the general formulas of the nonequilibrium diagram technique can be used in problems of tunnel planar structures described in the effective mass approach. The relation between such a “continual” approach and the tunneling Hamiltonian method is established, and the applicability conditions for this method are determined. The effects beyond the applicability limits of the tunneling Hamiltonian method, which can be described by the continual approach, are considered.