Prof. Dr. Alexander W. Holleitner

Technische-Universität München Walter Schottky Institut Am Coulombwall 3 85748 Garching

Tel: 089/289 12775 Fax: 089/320 6620 Email: holleitner@wsi.tum.de

Optoelectronic Detection of Non-Equilibrium Spin Transport in the Mesoscopic Regime in Semiconductor Nanostructures

A mesoscopic spin detector shall be lithographically built to detect an optically induced spin population in a two-dimensional electron reservoir of a semiconductor heterostructure. The optoelectronic spin detector shall exploit spin-split one-dimensional subbands of a quantum wire and it shall explore mesoscopic spin-transport phenomena of a non-equilibrium spin population in the diffusive and the ballistic regime. Particular emphasize will be placed on spin scattering processes at the transition from a two-dimensional to a onedimensional system. By orienting the spin detector along different crystallographic directions, we furthermore expect insights into spin relaxation mechanisms induced by spin-orbit coupling terms, i.e. due to structural and bulk inversion asymmetry. The proposed spin detector shall prepare ground for an optoelectronic spin device, which exploits the specific non-linearity in the current-voltage characteristics and the one-dimensional density of states of a quantum wire. To this end, the mesoscopic spin detector shall be optoelectronically characterized as a function of photon wavelength, polarization, source/drain voltage, external magnetic field, and temperature. In order to photo-excite the spin population, an ultra-short, pulsed, wavelength-tunable laser system will be used. The tunability allows measuring the photo-conductance close to the absorption edge of the lowdimensional electron system, while a pulsed laser system offers the possibility to define electron spin packages for spinelectronic time-of-flight experiments. 2. State of the Art, Preliminary Work