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Coherent Transport through Systems of Coupled Quantum Dots

100%
Trocha P., Barnaś J.
Acta Physica Polonica A
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2007
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vol. 112
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issue 2
473-480
EN
Spin-dependent electronic transport through two coupled single-level quantum dots attached to ferromagnetic leads with parallel and antiparallel magnetizations is analyzed theoretically. The intra-dot Coulomb correlation is taken into account, while the inter-dot Coulomb repulsion is omitted. Conductance and tunnel magnetoresistance associated with magnetization rotation are calculated by the nonequilibrium Green function technique. The relevant Green functions are derived by the equation of motion method in the Hartree-Fock approximation. The dot occupation numbers and the Green functions are calculated self-consistently. The interference effects in electronic transport through quantum dots are analyzed in two different configurations. It is shown that the Fano resonance in conductance can be observed even for vanishing inter-dot hopping parameter t. The interplay of the interference effects and the Coulomb interactions in quantum dots is also analyzed.
2
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Phonon-Assisted Electronic Transport through Double Quantum Dot System Coupled to Ferromagnetic Leads

100%
Trocha P., Rudziński W.
Acta Physica Polonica A
|
2013
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vol. 124
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issue 5
843-845
EN
Phonon-assisted electronic tunneling is studied through a double quantum dot coupled in parallel to ferromagnetic electrodes. The current-voltage characteristics for the system are derived within the nonequilibrium Green function technique based on equation of motion. It is found that additional phonon-induced resonance peaks appear in the spectral function on both sides of the main resonances corresponding to the quantum dot energy levels. It is shown that the "molecular-like" resonances are reproduced in the phonon side bands in the differential conductance. A significant phonon-induced enhancement of tunnel magnetoresistance as well as tunnel magnetoresistance oscillations are also predicted.
3
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Andreev Transport in Double Quantum Dot Cooper Pair Splitters in the Presence of External Magnetic Field

100%
Trocha P., Weymann I.
Acta Physica Polonica A
|
2015
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vol. 127
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issue 2
502-504
EN
The effect of external magnetic field on the transport properties of double quantum dots coupled to normal and superconducting leads is studied by means of the real-time diagrammatic technique in the sequential tunneling regime. This device works as a gate-controlled Cooper pair splitter. We focus on the transport regime where the current is blocked due to the spin triplet blockade. It is shown that external magnetic field can modify the Andreev current and differential conductance. In particular, magnetic field can suppress the negative differential conductance associated with the triplet blockade.
4
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Thermoelectric and Interference Effects in a Kondo-Correlated Quantum Dot with Rashba Spin-Orbit Coupling

81%
Karwacki Ł., Trocha P., Barnaś J.
Acta Physica Polonica A
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2013
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vol. 124
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issue 5
901-904
EN
Thermoelectric effects in spin-polarized transport through a strongly correlated quantum dot coupled to two ferromagnetic leads is investigated theoretically by means of the finite-U slave boson technique. The dot is coupled to the leads both symmetrically via the spin-conserving tunneling processes and asymmetrically via spin-nonconserving Rashba-induced tunneling terms. The asymmetric coupling leads to various interference effects which modify transport properties. We have analyzed such thermoelectric coefficients like the electronic contribution to heat conductance κ, thermopower S, and thermoelectric efficiency ZT.
5
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Spin Thermoelectric Effects in Transport through a Two-Level Quantum Dot Coupled to Ferromagnetic Leads

81%
Karwacki Ł., Trocha P., Barnaś J.
Acta Physica Polonica A
|
2012
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vol. 121
|
issue 5-6
1207-1209
EN
We investigate spin thermoelectric effects in a two-level quantum dot attached to external ferromagnetic leads. The basic thermoelectric coefficients are calculated by means of the non-equilibrium Green functions approach in the mean field approximation for the Coulomb term. Specifically, we calculate spin-dependent thermopower (spin Seebeck coefficient) and the charge thermopower. These coefficients measure spin and charge voltage drops across the device, respectively. Moreover, the figure of merit and its spin analog (which measures the spin thermoelectric efficiency) are presented and discussed. We also show that the indirect (via the leads) coupling between the dot's levels can significantly enhance the thermoelectric effects.
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