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Influence of electron-phonon coupling on transport through the quantum dot in the Kondo regime

Renata G. Świrkowicz ,  M. Wilczyński 

Warsaw University of Technology, Faculty of Physics, Koszykowa 75, Warszawa 00-662, Poland

Abstract

Recent experimental data on electron transport through molecules and quantum dots have allowed to observe phonon satellites in the Kondo regime. Transport through a quantum dot attached to non-magnetic or ferromagnetic electrodes is studied theoretically within the non-equilibrium Green function formalism and effects of local vibrational modes are analyzed for different values of parameter g describing the coupling strength of electron-phonon systems. A presence of phonons strongly influences the spectral function and the differential conductance leading to an appearance of phonon satellites on both sides of the main Kondo anomaly. When the dot is attached to ferromagnetic electrodes with parallel magnetic moments the Kondo resonance is split due to the effective field generated by electrodes. The main components move away from the zero bias limit as polarization of electrodes increases. The Kondo satellites move accordingly and develop in a distance equal to the phonon energy from each Kondo component. The Kondo effect is strongly reduced due to polarization of electrodes and due to coupling to phonon bath. In systems in which spin voltage Vs  is applied together with transport voltage Ve spin current Is and charge current Ie can be carried out. The influence of electron-phonon coupling on the spin conductance Gs=dIs/dVs and the charge conductance Ge=dIe/dVs is discussed in detail. Gs reveals the dependence similar to that found for junction with ferromagnetic electrodes with two Kondo resonances accompanied by phonon satellites, but quite different behaviour is obtained for the charge conductance.

 

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Related papers

Presentation: Poster at E-MRS Fall Meeting 2008, Symposium J, by Renata G. Świrkowicz
See On-line Journal of E-MRS Fall Meeting 2008

Submitted: 2008-05-29 10:41
Revised:   2009-06-07 00:48