V. N. Mantsevich

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

It was found that tunneling current through a nanometer scale structure with strongly coupled localized states causes spatial redistribution of localized charges induced by Coulomb correlations. We present here theoretical investigation of this effect by means of Heisenberg equations for localized states electron filling numbers. This method makes it possible to take into account pair correlations of local electron density exactly. It is shown that inverse occupation of the two-level system caused by Coulomb correlations appears in particular range of applied bias. Described effects can give a possibility of charge manipulation in the proposed system. We also expect that described results can be observed in tunneling structures with impurities or with small quantum dots.

The effect of coulomb correlations on the nonequilibrium charge redistribution tuned by the tunneling current

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

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

Abstract 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.

Nonadiabatic electron charge pumping in coupled semiconductor quantum dots

The possibility of nonadiabatic electron pumping in the system of three coupled quantum dots (QDs) attached to the leads is discussed. We have found out that periodical changing of energy level position in the middle QD results in non-zero mean tunneling current appeared due to nonadiabatic 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.

Metallic glass electronic structure peculiarities revealed by UHV STM/STS

We present the results of ultrahigh vacuum scanning tunneling microscopy/spectroscopy investigation of metallic glass surface. The topography and electronic structure of Ni63.5Nb36.5 have been studied. A great number of clusters with size about 5–10 nm have been found on constant current scanning tunneling microscopy images. The tunneling spectra of normalized tunneling conductivity revealed the energy pseudogap in the vicinity of Fermi energy. For energy values above 0.1 eV the normalized tunneling conductivity changes linearly with increasing of tunneling bias. The obtained results can be understood within suggested theoretical model based on the interplay of elastic electron scattering on random defects and weak intra-cluster Coulomb interaction. The effects of the finite edges of electron spectrum of each cluster have to be taken into account to explain the experimental data. The tunneling conductivity behavior and peculiarities in current images of individual clusters can also be qualitatively analyzed in the framework of suggested model.

Two-dimensional dynamic photonic crystal creation by means of three non-coplanar laser beams interference in colloidal CdSe/ZnS quantum dots solution

We demonstrated a simple way to create dynamic photonic crystals with different lattice symmetry by interference of three non-coplanar laser beams in colloidal solution of CdSe/ZnS quantum dots. Two-dimensional dynamic photonic crystal was formed due to the periodical changing of refraction and/or absorption of resonantly excited excitons in CdSe/ZnS quantum dots. The formation of dynamic photonic crystal was confirmed by the observed diffraction of the beams that have excited photonic crystal at the angles equal to that calculated for the corresponding two-dimensional lattice (self-diffraction regime).

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.

Effect of different impurity atoms on 1/fα tunneling current noise characteristics on InAs (110) surface

The results of UHV STM investigations of tunneling current noise spectra in the vicinity of individual impurity atoms on the InAs(110) surface are reported. It was found that the power law exponent of 1/fα noise depends on the presence of an impurity atom in the tunneling junction area. This is consistent with the proposed theoretical model considering tunneling current through a two-state impurity complex model system taking into account many-particle interaction.

Direct visualization of Ni-Nb bulk metallic glasses surface: From initial nucleation to full crystallization

This article is devoted to in situ investigation of the Ni-based bulk metallic glass structural evolution and crystallization behavior by scanning tunneling microscopy/spectroscopy. The possibility of different surface nanostructures formation is shown by annealing of an original bulk glassy alloy in ultra high vacuum. Atomic locations in these surface nanostructures are completely different from those formed according to Ni-Nb binary phase diagram in the bulk area of the sample. The validity of the results is also verified by transmission electron microscopy and nano-beam diffraction measurements.

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

We investigated the tunneling current peculiarities in the system of two quantum dots that are coupled by means of the external field and are weakly connected to the electrodes in the presence of Coulomb correlations. It was found that tuning of the Rabi frequency induces fast multiple tunneling current switching and leads to the negative tunneling conductivity. Special role of multielectron states was demonstrated. Moreover we revealed conditions for bistable behavior of the tunneling current in the coupled quantum dots with Coulomb correlations.