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N. S. Maslova

Publications and source records attributed to N. S. Maslova.

33 records · Page 2Linked to original sources
arXiv2011

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.

cond-mat.mes-hall↗
arXiv2011

The effect of Coulomb correlations on non-equilibrium charge redistribution tuned by the tunneling current

It was shown that tunneling current flowing through a system with Coulomb correlations leads to charge redistribution between the different localized states. Simple model consisting of two electron levels have been analyzed by means of Heisenberg motion equations taking into account all order correlations of electron filling numbers in localized states exactly. We consider various relations between Coulomb interaction and localized electron energies. Sudden jumps of electron density at each level in a certain range of applied bias have been found. We found that for some parameter range inverse occupation in the two-level system appeared due to Coulomb correlations. It was shown also that Coulomb correlations lead to appearance of negative tunneling conductivity at certain relation between the values of tunneling rates from the two electronic levels.

cond-mat.other↗
arXiv2011

Correlation induced switching of local spatial charge distribution in two-level system

We present theoretical investigation of spatial charge distribution in the two-level system with strong Coulomb correlations by means of Heisenberg equations analysis for localized states total electron filling numbers taking into account pair correlations of local electron density. It was found that tunneling current through nanometer scale structure with strongly coupled localized states causes Coulomb correlations induced spatial redistribution of localized charges. Conditions for inverse occupation of two-level system in particular range of applied bias caused by Coulomb correlations have been revealed. We also discuss possibility of charge manipulation in the proposed system.

cond-mat.mes-hall↗
arXiv2011

The influence of tunneling matrix elements modification due to on-site Coulomb interaction on local tunneling conductivity

Interplay between changes of energy levels and tunneling amplitudes caused by localized electrons on-site Coulomb interaction depending on non-equilibrium electron filling numbers is analyzed. Specific features of local tunneling conductivity spectra for different positions of localized states energy relative to the Fermi level have been investigated by means of self-consistent mean field approximation in the presence of non-equilibrium effects. The conditions when modifications of tunneling transfer amplitude due to changes of electron filling numbers in the presence of on-site Coulomb interaction should be taken into account in tunneling conductivity spectra have been revealed.

cond-mat.mes-hall↗
arXiv2010

Spatial distribution of local tunneling conductivity due to interference and Coulomb interaction effects for deep and shallow impurities on semiconductor surfaces

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).

cond-mat.mes-hall↗
arXiv2009

Spatial effects of Fano resonance in local tunneling conductivity in vicinity of impurity on semiconductor surface

We present the results of local tunneling conductivity spatial distribution detailed theoretical investigations in vicinity of impurity atom for a wide range of applied bias voltage. We observed Fano resonance in tunneling conductivity resulting from interference between resonant tunneling channel through impurity energy level and direct tunneling channel between the tunneling contact leads. We have found that interference between tunneling channels strongly modifies form of tunneling conductivity measured by the scanning tunneling microscopy/spectroscopy (STM/STS) depending on the distance value from the impurity.

cond-mat.mes-hall↗
arXiv2009

Spatial distribution of local density of states in vicinity of impurity on semiconductor surface

We present the results of detailed theoretical investigations of changes in local density of total electronic surface states in 2D anisotropic atomic semiconductor lattice in vicinity of impurity atom for a wide range of applied bias voltage. We have found that taking into account changes in density of continuous spectrum states leads to the formation of a downfall at the particular value of applied voltage when we are interested in the density of states above the impurity atom or even to a series of downfalls for the fixed value of the distance from the impurity. The behaviour of local density of states with increasing of the distance from impurity along the chain differs from behaviour in the direction perpendicular to the chain.

cond-mat.mes-hall↗
arXiv2008

Tuning of tunneling current noise spectra singularities by localized states charging

We report the results of theoretical investigations of tunneling current noise spectra in a wide range of applied bias voltage. Localized states of individual impurity atoms play an important role in tunneling current noise formation. It was found that switching "on" and "off" of Coulomb interaction of conduction electrons with two charged localized states results in power law singularity of low-frequency tunneling current noise spectrum ($1/f^α$) and also results on high frequency component of tunneling current spectra (singular peaks appear).

cond-mat.mtrl-sci↗
arXiv2008

The influence of localized states charging on 1/f^α tunneling current noise spectrum

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 the 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.

cond-mat.mtrl-sci↗
arXiv2007

Low-temperature scanning tunneling microscopy of ring-like surface electronic structures around Co islands on InAs(110) surfaces

We report on the experimental observation by scanning tunneling microscopy at low temperature of ring-like features that appear around Co metal clusters deposited on a clean (110) oriented surface of cleaved p-type InAs crystals. These features are visible in spectroscopic images within a certain range of negative tunneling bias voltages due to the presence of a negative differential conductance in the current-voltage dependence. A theoretical model is introduced, which takes into account non-equilibrium effects in the small tunneling junction area. In the framework of this model the appearance of the ring-like features is explained in terms of interference effects between electrons tunneling directly and indirectly (via a Co island) between the tip and the InAs surface.

cond-mat.mtrl-sci↗
arXiv2006

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.

cond-mat.mes-hall↗
arXiv1999

Influence of resonant tunneling on the imaging of atomic defects on InAs(110) surfaces by low-temperature scanning tunneling microscopy

We have used a low-temperature scanning tunneling microscope (STM) to study the surface of heavily doped semiconductor InAs crystals. The crystals are cleaved in situ along the (110) plane. Apart from atomically flat areas, we also observe two major types of atomic scale defects which can be identified as S dopant atoms and as As vacancies, respectively. The strong bias voltage dependence of the STM image of the impurities can be explained in terms of resonant tunneling through localized states which are present near the impurity.

cond-mat.mtrl-sci↗
arXiv1999

Scanning tunneling microscopy and spectroscopy at low temperatures of the (110) surface of Te doped GaAs single crystals

We have performed voltage dependent imaging and spatially resolved spectroscopy on the (110) surface of Te doped GaAs single crystals with a low temperature scanning tunneling microscope (STM). A large fraction of the observed defects are identified as Te dopant atoms which can be observed down to the fifth subsurface layer. For negative sample voltages, the dopant atoms are surrounded by Friedel charge density oscillations. Spatially resolved spectroscopy above the dopant atoms and above defect free areas of the GaAs (110) surface reveals the presence of conductance peaks inside the semiconductor band gap. The appearance of the peaks can be linked to charges residing on states which are localized within the tunnel junction area. We show that these localized states can be present on the doped GaAs surface as well as at the STM tip apex.

cond-mat.mtrl-sci↗
arXiv1998

Phonon assisted tunneling in Josephson junctions

The expression for additional subgap current in the presence of electron-phonon interaction is derived. We show that the phonon assisted tunneling leads to appearance of peaks on current-voltage characteristics at the Josephson frequencies corresponding to the Raman-active phonons. The relation of the obtained results to experimental observations are discussed.

cond-mat.supr-con↗