Dresden 2006 – wissenschaftliches Programm

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TT: Tiefe Temperaturen

TT 21: Transport: Nanoelectronics II - Spintronics and Magnetotransport - Part 2

TT 21.2: Vortrag

Dienstag, 28. März 2006, 16:30–16:45, HSZ 105

Spin-dependent Transport through Quantum Dots connected to Three Ferromagnetic Leads — •Daniel Urban, Matthias Braun, and Jürgen König — Ruhr-Universität Bochum, 44780 Bochum, Germany

Transport through a non-magnetic, single-level quantum-dot with ferromagnetic leads is investigated in the sequential tunneling regime by a real-time diagrammatic technique. If a current is forced through the system, spin accumulates on the dot, which reduces transport (spin-valve effect). The interplay of Coulomb interaction and ferromagnetism gives rise to an exchange field [1], in which the spin precesses so that transport is enhanced.

We consider setups in which a current flows only between two of the leads. The third lead is kept current-free and enters only by its ferromagnetic properties.

The two systems analyzed are a quantum dot spin-flip transistor with coplanar magnetizations and a setup with pairwise orthogonal lead magnetizations. In both cases spin precession due to the third lead further enhances transport while in the latter we additionally observe asymmetries in the conductances under current reversal.

[1] M. Braun, J. König, and J. Martinek, Phys. Rev. B 70, 195345 (2004)