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1
Content available remote Spin-polarized transport through two quantum dots: interference and Coulomb correlation effects
Trocha P., Barnaś J.
Materials Science Poland
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2008
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Vol. 26, No. 3
708--714
EN
Electronic transport through two single-level quantum dots attached in parallel to ferromagnetic leads has been analyzed theoretically. The intra-dot Coulomb correlation was taken into account, while the inter-dot hopping and Coulomb repulsion have been neglected. The dots, however, may interact via the external leads when the off-diagonal elements of the coupling matrix do not vanish. Conductance and tunnel magnetoresistance associated with the magnetization rotation from antiparallel to parallel configurations are calculated by the non-equilibrium Green function technique. The relevant Green functions are derived from the appropriate equation of motion in the Hartree–Fock approximation. We focus on the interference effects due to nonzero off-diagonal elements of the coupling matrix.
2
Content available remote Interference and Coulomb correlation effects in spin-polarized transport through coupled quantum dots
Trocha P., Barnaś J.
Materials Science Poland
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2007
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Vol. 25, No. 2
545--552
EN
Spin-dependent transport through two coupled single-level quantum dots attached to ferromagnetic leads with collinear (parallel and antiparallel) magnetizations is analyzed theoretically. The intra-dot Coulomb correlation is taken into account, whereas the inter-dot Coulomb repulsion is neglected. Transport characteristics, including conductance and tunnel magnetoresistance associated with the magnetization rotation from parallel to antiparallel configurations, are calculated by the noneqiulibrium Green function technique. The relevant Green functions are derived by the equation of motion method in the Hartree-Fock approximation. We have found a splitting of the Fano peak, induced by the intra-dot Coulomb interaction. Apart from this, the intra-dot electron correlations are shown to lead to an enhancement of the tunnel magnetoresistance effect.
3
Content available remote Transport characteristics of ferromagnetic single-electron transistors with non-collinear magnetizations
Wiśniewska J., Kowalik M., Barnaś J.
Materials Science Poland
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2006
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Vol. 24, No. 3
761--767
EN
Theoretical analysis of spin-polarized transport through a ferromagnetic single-electron transistor (FM SET) has been carried out in the sequential tunneling regime. Two external electrodes and the central part (island) of the device are assumed to be ferromagnetic, with the corresponding magnetizations being generally non-collinear. Transport properties of the FM SET are analyzed within the master equation approach, with the respective transition rates determined from the Fermi golden rule. It is assumed that spin relaxation processes on the island are sufficiently fast to neglect spin accumulation. It is shown that electric current and tunnel magnetoresistance (TMR) strongly depend on magnetic configuration of the device. Transport characteristics of symmetrical and asymmetrical structures have been calculated as a function of bias and the gate voltages.
4
Content available remote Resonant tunneling through a single level quantum dot attached to ferromagnetic leads with non-collinear magnetizations
Wawrzyniak M., Gmitra M., Barnaś J.
Materials Science Poland
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2006
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Vol. 24, No. 3
695--700
EN
Resonant tunnelling through a non-interacting single-level quantum dot attached to ferromagnetic leads is analysed theoretically. The magnetic moments of the leads are assumed to be non-collinear. Apart from this, an external magnetic field is applied to the system, which is non-collinear with the magnetizations. The magnetic moments of the leads and the external magnetic field are, however, in a common plane. Basic transport characteristics, including current-voltage curves, differential conductance, and tunnel magnetoresistance associated with magnetization rotation, are calculated using the non-equilibrium Green function technique. The dependence of transport characteristics on the bias voltage has been calculated numerically.
5
Content available remote Spin-dependent transport in ferromagnetic single-electron transistors with non-collinear magnetizations
Wiśniewska J., Weymann I., Barnaś J.
Materials Science Poland
|
2004
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Vol. 22, No. 4
461--467
EN
Electronic transport in a ferromagnetic single-electron transistor is analysed theoretically in the sequential tunnelling regime. One of the external electrodes and the central part (island) of the device are assumed to be ferromagnetic, with the corresponding magnetizations being non-collinear. The analysis is based on the master equation method, and the respective transition rates are determined from the Fermi golden rule. It is shown that the electric current and corresponding tunnel magnetoresistance (TMR) strongly depend on the angle between the magnetizations. For an arbitrary magnetic configuration, TMR is modulated by charging effects, which give rise to characteristic dips (cusps) at the bias voltages corresponding to the Coulomb steps in the current-voltage characteristics.
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