Coherent spin transport in III-V semiconductors

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We have focused on developing electrical methods for generating and manipulating coherent spin states in III-V semiconductor structures without magnetic electrodes. We propose for the next funding period to combine these methods, which would allow to generate and to manipulate coherent spins all-electrically by two time-delayed electric field pulses. Furthermore, we propose a scheme for spin dependent coherent electrical detection. While in this experiment spins shall be generated by optical orientation, we suggest using timeresolved spin photo-voltage measurements as an electrical probe for coherent spin currents. The controlled optical excitation of electron spins in perpendicular directions shall furthermore be used to study spin relaxation anisotropy. In a second focus, we will extend our spin transport studies to semiconductor nanowires. We propose two experiments of different complexity. 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, we propose to optically generate spin currents in the nanowires. The spin currents shall be probed either directly by photo-voltages or by magnetoresistive changes when using ferromagnetic electrodes as spin detectors.