Vladimir N. Mantsevich

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.

Different behaviour of local tunneling conductivity for deep and shallow impurities due to Coulomb interaction

Spatial distribution of local tunneling conductivity was investigated for deep and shallow impurities on semiconductor surfaces. Non-equilibrium Coulomb interaction and interference effects were taken into account and analyzed theoretically with the help of Keldysh formalism. Two models were investigated: mean field self-consistent approach for shallow impurity state and Hubbard-I model for deep impurity state. We have found that not only above the impurity but also at the distances comparable to the lattice period both effects interference between direct and resonant tunneling channels and on-site Coulomb repulsion of localized electrons strongly modifies form of tunneling conductivity measured by the scanning tunneling microscopy/spectroscopy (STM/STS).

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.

The influence of localized states charging on 1/fα tunneling current noise spectrum

Abstract We report the results of theoretical investigations of low frequency tunneling current noise spectra component ( 1 / f α ). Localized states of individual impurity atoms play a key role in low frequency tunneling current noise formation. It is found that switching “on” and “off” of Coulomb interaction of conduction electrons with one or two charged localized states results in power law singularity of low-frequency tunneling current noise spectrum 1 / f α . Power law exponent in different low frequency ranges depends on the relative values of Coulomb interaction of conduction electrons with different charged impurities.

Comparison of pure and combined search strategies for single and multiple targets

AbstractnWe address the generic problem of random search for a point-like target on a line. Using the measures of search reliability and efficiency to quantify the random search quality, we compare Brownian search with Lévy search based on long-tailed jump length distributions. We then compare these results with a search process combined of two different long-tailed jump length distributions. Moreover, we study the case of multiple targets located by a Lévy searcher.n

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.

Non-stationary spin-polarized tunneling currents tuning by means of applied bias changing

We study time evolution of the opposite spin electron occupation numbers for the single Anderson impurity localized between two macroscopic leads in the presence of applied bias voltage. It was shown that non-stationary spin-polarized currents are present in the both leads and their polarization and direction in each lead can be controlled by the the applied bias voltage changing.

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.