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Coupled Quantum Dots - Spatial Correlations between Interacting Carriers

100%
Szafran B.
Acta Physica Polonica A
|
2008
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vol. 114
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issue 5
1013-1039
EN
We review results of our modeling of excitons and excitonic trions confined in vertically stacked InGaAs/GaAs self-assembled quantum dots. Electrons and holes in double quantum dots are much more significantly correlated than in a single dot. For that reason our modeling was based on simple confinement potentials that allow for an exact diagonalization of the resulting two- and three-particle Hamiltonians with a precise account for the relative electron and hole localization along the stack. We studied the optical signatures of the coupling in context of the photoluminescence experiments performed in the external electric field. The calculations predicted prior to the experiment the mechanism of the exciton and negative trion dissociation by electron removal from the dot occupied by the hole. We discuss the competition between the tunnel and the electrostatic interdot couplings. Effects of the non-perfect alignment of the dots as well as stacks containing more than two dots are also discussed.
2
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Transport and Capacitance Spectroscopy of Quantum Dots

51%
Adamowski J., Bednarek S., Szafran B.
Acta Physica Polonica A
|
2001
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vol. 100
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issue 2
145-163
EN
A review of recent theoretical studies on a single-electron tunneling in quantum dots is presented. This effect underlies the transport spectroscopy performed on the vertical gated quantum dots and the capacitance spectroscopy on the self-assembled quantum dots. The conditions of the single-electron tunneling are formulated in terms of electrochemical potentials of the electrons in the leads and in the quantum dot. The electrochemical potentials for the electrons confined in the quantum dots can be calculated by solving the many-electron Schrödinger equation. The results obtained by the Hartree-Fock method are presented. For the vertical gated quantum dot, the realistic confinement potential is obtained from the Poisson equation. The application of the self-consistent procedure to the solution of the Poisson-Schrödinger problem is discussed. The calculated positions of the current peaks at zero bias and boundaries of the Coulomb diamonds for non-zero bias are in good agreement with experiment. The influence of an external magnetic field on the single-electron tunneling is also discussed. The spin-orbital configurations of the electrons confined in the quantum dots change with the magnetic field, which leads to features observed in the current-voltage and capacitance-voltage characteristics.
3
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Electron Pairs and Excitons in Quasi-One-Dimensional Nanostructures

51%
Bednarek S., Szafran B., Chwiej T., Adamowski J.
Acta Physica Polonica A
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2003
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vol. 103
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issue 6
567-572
EN
A theoretical study of two-particle systems in quasi-one-dimensional quantum wires and quantum dots is presented. We have derived the analytical formula for the effective interaction potential between the charge carriers confined laterally by a strong parabolic potential and applied this formula to electron pairs in single and double quantum dots and to excitons in quantum wires. In the single quantum dot of the sufficiently large size, we have found the Wigner-type localization.
4
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Theoretical Description of Shell Filling in Cylindrical Quantum Dots

51%
Szafran B., Bednarek S., Adamowski J.
Acta Physica Polonica A
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1998
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vol. 94
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issue 3
555-559
EN
A theoretical quantitative description is given for non-periodic oscillations observed in a current vs. gate voltage characteristics of cylindrical quantum dots. Energy eigenvalues and chemical potentials for a system of N confined electrons (N=1,...,13) are calculated by the unrestricted Hartree-Fock method with a confinement potential proportional to the gate voltage. The positions of the observed peaks of the current are reproduced with a very good accuracy. The non-periodicity of the characteristic is explained as a result of the shell filling, which is a signature of the quantum Coulomb blockade.
5
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Nanodevice for High Precision Readout of Electron Spin

51%
Szumniak P., Bednarek S., Szafran B., Grynkiewicz P.
Acta Physica Polonica A
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2011
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vol. 119
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issue 5
651-653
EN
In this paper we propose and simulate operation of a nanodevice, which enables the electron spin accumulation and very precise read-out of its final value. We exploit the dependence of the electron trajectory on its spin state due to the spin-orbit coupling in order to distinguish between different spin orientations.
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