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 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.Comment: 6 pages, 9 figure

Tunneling current induced phonon generation in nanostructures

We analyze generation of phonons in tunneling structures with two electron states coupled by electron-phonon interaction. The conditions of strong vibration excitations are determined and dependence of non-equilibrium phonon occupation numbers on the applied bias is found. For high vibration excitation levels self consistent theory for the tunneling transport is presented.Comment: 11 pages, 6 figure

Non-adiabatic electron charge pumping in coupled semiconductor quantum dots

The possibility of non-adiabatic electron pumping in the system of three coupled quantum dots attached to the leads is discussed. We have found out that periodical changing of energy level position in the middle quantum dot results in non zero mean tunneling current appeared due to non-adiabatic non-equilibrium processes. The same principle can be used for fabrication of a new class of semiconductor electronic devices based on non-stationary non-equilibrium currents. As an example we propose a nanometer quantum emitter with non-stationary inverse level occupation achieved by electron pumping.Comment: 6 pages, 4 figure

Non-stationary effects in the coupled quantum dots influenced by the electron-phonon interaction

We analyzed time evolution of the localized charge in the system of two interacting single level quantum dots (QDs) coupled with the continuous spectrum states in the presence of electron-phonon interaction. We demonstrated that electron-phonon interaction leads to the increasing of localized charge relaxation rate. We also found that several time scales with different relaxation rates appear in the system in the case of non-resonant tunneling between the dots. We revealed the formation of oscillations in the filling numbers time evolution caused by the emission and adsorption processes of phonons.Comment: 6 pages, 2 figure

Tunneling transport through multi-electrons states in coupled quantum dots with Coulomb correlations

We investigated the peculiarities of non-equilibrium charge configurations in the system of two strongly coupled quantum dots (QDs) weakly connected to the reservoirs in the presence of Coulomb correlations. We revealed that total electron occupation demonstrates in some cases significant decreasing with increasing of applied bias - contrary to the situation when Coulomb correlations are absent and found well pronounced ranges of system parameters where negative tunneling conductivity appears due to the Coulomb correlations.Comment: 7 pages, 3 figures. arXiv admin note: substantial text overlap with arXiv:1206.571

Kinetics of local ""magnetic"" moment and non-stationary spin-polarized current in the single impurity Anderson-model

We perform theoretical investigation of the localized state dynamics in the presence of interaction with the reservoir and Coulomb correlations. We analyze kinetic equations for electron occupation numbers with different spins taking into account high order correlation functions for the localized electrons. We reveal that in the stationary state electron occupation numbers with the opposite spins always have the same value - the stationary state is a $"$paramagnetic$"$ one. $"$Magnetic$"$ properties can appear only in the non-stationary characteristics of the single-impurity Anderson model and in the dynamics of the localized electrons second order correlation functions. We found, that for deep energy levels and strong Coulomb correlations, relaxation time for initial $"$magnetic$"$ state can be several orders larger than for $"$paramagnetic$"$ one. So, long-living $"$magnetic$"$ moment can exist in the system. We also found non-stationary spin polarized currents flowing in opposite directions for the different spins in the particular time interval.Comment: 7 pages, 7 figure

Localized charge bifurcation in the coupled quantum dots

We analyzed theoretically localized charge relaxation in a double quantum dot (QD) system coupled with continuous spectrum states in the presence of localized electrons Coulomb interaction in a single QD. We have found that for a wide range of system parameters charge relaxation occurs through two stable regimes with significantly different relaxation rates. A peculiar time moment exists in the system at which rapid switching between stable regimes takes place. We consider this phenomenon to be applicable for creation of active elements in nano-electronics based on the fast transition effect between two stable states.Comment: 7 pages, 4 figure

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

We reveal that for the single Anderson impurity localized between non-magnetic leads of the tunneling contact $"$magnetic$"$ state can be distinguished from the $"$paramagnetic$"$ one only by the analysis of the non-stationary system characteristics or the behavior of the second order correlation functions for the localized electrons occupation numbers. We investigate the response of the system to the sudden shift of the applied bias and to the switching $"$on$"$ the coupling to the second lead of the tunneling contact. We demonstrate that in addition to the changes of the relaxation regimes and typical relaxation time scales, non-stationary spin-polarized currents flowing in the both leads are present in the system. 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.Comment: 9 pages, 9 figures. arXiv admin note: text overlap with arXiv:1606.0897

External field induced switching of tunneling current in the coupled quantum dots

We investigated the tunneling current peculiarities in the system of two coupled by means of the external field quantum dots (QDs) weakly connected to the electrodes in the presence of Coulomb correlations. It was found that tuning of the external field frequency induces fast multiple tunneling current switching and leads to the negative tunneling conductivity. Special role of multi-electrons states was demonstrated. Moreover we revealed conditions for bistable behavior of the tunneling current in the coupled QDs with Coulomb correlations.Comment: 6 pages, 2 figures. arXiv admin note: text overlap with arXiv:1206.5714, arXiv:1407.057

Quenched dynamics of entangled states in correlated quantum dots

Time evolution of initially prepared entangled state in the system of coupled quantum dots has been analyzed by means of two different theoretical approaches: equations of motion for the all orders localized electron correlation functions, considering interference effects, and kinetic equations for the pseudo-particle occupation numbers with constraint on the possible physical states. Results obtained by means of different approaches were carefully analyzed and compared with each other. Revealed direct link between concurrence (degree of entanglement) and quantum dots pair correlation functions allowed us to follow the changes of entanglement during time evolution of the coupled quantum dots system. It was demonstrated that the degree of entanglement can be controllably tuned during the time evolution of quantum dots system.Comment: 8 pages, 3 figure