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Research Unit “Coherence and relaxation properties of electron spins”

Recently, the proposals of second three-years funding period for the Research Unit “Coherence and relaxation properties of electron spins” was positively evaluated by the referees of the German Science Foundation (DFG). The Peter Grünberg Institute (PGI-9) contributes to the Research Unit with the project: Coherent spin transport in III-V semiconductors.

Within the research unit, fundamentals of spin relaxation and coherence are tackled. On the one hand, we investigate III-V-semiconductors, which serve as a reference and model system to introduce novel cutting-edge methodology with respect to spin coherence and manipulation. On the other hand, novel materials will be investigated determining their dynamic spin properties and introducing novel concepts for an envisioned spin functionality. In all three materials classes, the intricate nature of spin dynamics requires a strong theoretical backing including novel numerical methods for a versatile application to the different materials classes. These approaches will be developed based on the current forefront approaches in, e.g., density functional, quantum Monte Carlo, and time-dependent density matrix renormalization group methods.

In the last period of the project jointly conducted by the II. Institute of Physics, RWTH Aachen, and the Peter Grünberg Institute (PGI-9) we focused on developing electrical methods for generating and manipulating coherent spin states in III-V semiconductor structures without magnetic electrodes. In the new funding period these methods will be combined.  Furthermore our spin transport studies will be extended to semiconductor nanowires.  Firstly, we will fabricate non-local spin-valves for spin injection and detection using ferromagnetic electrodes and MgO as injection barrier. Conventional magneto-transport including electrical Hanlé measurements shall be used to determine spin relaxation times and lengths. Secondly, optically generated spin currents in the nanowires will be investigated.

Nanowire-ferromagnet-structureNanowire-ferromagnet-structure for measurements in a non-local geometry