Dresden 2003 – wissenschaftliches Programm
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TT: Tiefe Temperaturen
TT 1: Mesoskopische Systeme I
TT 1.3: Vortrag
Montag, 24. März 2003, 10:15–10:30, HSZ03
Interaction-induced spin rotation and the Kondo effect in quantum dots coupled to ferromagnetic leads — •Jürgen König1 and Jan Martinek1,2 — 1Institut für Theoretische Festkörperphysik, Universität Karlsruhe — 2Institute of Molecular Physics, Polish Academy of Sciences, Poznan, Poland
We study quantum dots coupled to ferromagnetic leads. First, we analyze the Kondo effect for parallel and antiparallel orientation of the leads’ magnetization as a function of the spin polarization in the leads [1]. Based on a scaling approach we predict that for parallel alignment of the magnetizations in the leads the strong-coupling limit of the Kondo effect is reached at a finite value of the magnetic field. Using an equations-of-motion technique we study nonlinear transport through the dot. For parallel alignment the zero-bias anomaly may be split even in the absence of an external magnetic field. For antiparallel spin alignment and symmetric coupling, the peak is split only in the presence of a magnetic field, but shows a characteristic asymmetry in amplitude and position.
Second, analyze lowest-order transport through the quantum dot for arbitrary orientation of the leads’ magnetization directions [2]. We find an interaction-induced rotation of the quantum-dot spin. This can be detected in the transport signal as a reduction of the spin-valve effect and a characteristic non-trivial dependence of the linear conductance on the relative angle between the magnetization directions in the leads.
[1] J. Martinek, Y. Utsumi, H. Imamura, J. Barnas, S. Maekawa, J. König, and G. Schön, cond-mat/0210006.
[2] J. König and J. Martinek, cond-mat/0212253.