Dresden 2011 – scientific programme

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MA: Fachverband Magnetismus

MA 63: Poster II (Surface Magnetism/ Magnetic Imaging/ Topological Insulators/ Spin Structures and Magnetic Phase Transitions/ Graphene/ Magnetic Thin Films/ Magnetic Semiconductors/ Magnetic Half-metals and Oxides/ Spin-dependent Transport/ Spin Excitations and Spin Torque/ Spin Injection and Spin Currents in Heterostructures/ Spintronics/ Magnetic Storage and Applications)

MA 63.72: Poster

Friday, March 18, 2011, 11:00–14:00, P2

Spintransport through magnetically doped Quantum Dots — •Christoph Hübner, Daniel Becker, and Daniela Pfannkuche — I. Institut für Theoretische Physik, Universität Hamburg, 20355 Hamburg.

Spin transport between two non-polarized electron reservoirs via an idealized single level quantum dot with an incorporated magnetic impurity is investigated. A real time diagrammatic transport theory, based on the Keldysh formalism, is used to determine the current between the leads and the non-equilibrium occupation of quantum dot states in stationary limit [1]. In the weak coupling regime one can derive a master equation for diagonal elements of the density matrix by perturbatively expanding to second order in hybridization. This formalism gives insight into sequential and coherent transport in the stationary limit. Up to first order the electron impurity interaction leads to differently pronounced signals of sequential transport channels visible in the differential conductivity. Also a new type of spin blockade is found which is tunable by the coupling strength between electron and impurity spin. In second order spin flip processes occur, which depend on the interaction strength and lead to a spin excitation in the quantum dot. Research is supported by GRK 1286,DFG-CH265/4-1 as well as by the Hamburg’s Excellence Cluster Spintronik.

[1] M. Leijnse, M.R. Wegewijs, Phys. Rev. B 78, 235424 2008