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HL: Halbleiterphysik

HL 37: Quantenpunkte und -drähte: Transporteigenschaften

HL 37.8: Vortrag

Donnerstag, 11. März 2004, 12:00–12:15, H13

Transport through a quantum dot spin valve — •Matthias Braun^1,2, Jan Martinek², and Jürgen König¹ — ¹Theoretische Physik III, Ruhr-Universität Bochum, D-44780 Bochum — ²Institut für Theoretische Festkörperphysik, Universität Karlsruhe, D-76128 Karlsruhe

We study transport through a quantum dot that is weakly coupled to ferromagnetic leads. The interesting aspect of this structure is that it combines two physical paradigms. Due to the polarized leads, the tunnel rates of the electrons becomes spin dependent leading to the spin valve effect. On the other hand the low capacity of a quantum dot strongly enhances the importance of electron-electron interaction leading to Coulomb blockade.

In a non-equilibrium situation spin accumulates on the dot for non-parallel aligned electrode magnetizations. Due to the interplay of Coulomb interaction and coupling to ferromagnetic leads, this accumulated spin experiences an exchange field which leads to spin precession.

Spin and charge accumulation as well as the precession of the accumulated spin in the exchange field influence the dot state. The resulting complex dynamics of the dot spin is visible in the linear and non-linear transport characteristics of the device.