OPTICAL ORIENTATION OF SPINS IN SEMICONDUCTORS USING THE FELIX AND FELBE FREE-ELECTRON LASER FACILITIES

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Optical orientation of spins in semiconductors is a well established field that takes advantage of the selection rules for circularly polarised photon absorption. Using short pulsed lasers information can be gained on the spin dynamics and control. The proposal focusses mainly on narrow gap III-V semiconductors (NGSs) because they offer advantages for spintronic devices (i.e. devices that depend on the manipulation of spin rather than charge), due to their high mobility and strong relativistic effects that couple the spin and orbital motion. The fact that the materials of choice have small bandgap immediately indicates that far-infrared sources are required for excitation of spins from the valence band to the conduction band. In addition, in this wavelength range one can gain valuable information about dynamics using intraband excitation (e.g. of conduction electrons in doped samples) in both narrow and wide gap materials. Intraand excitation is important if e.g. photo-excited holes influence electron spin dynamics in interband experiments, or if the material under investigation has an indirect gap. This proposal is based on collaboration between groups at Surrey and Heriot-Watt Universities with combined experience in the use of Free Electron Laser (FEL) facilities in infrared and optical characterisation of ultrafast processes. We wish to hire a project student, based at Surrey, to study spin dynamics in bulk and quantum well (QW) structures of InSb and InAs at the FEL facilities, FELIX (at Utrecht) and FELBE (at Dresden). A key aspect of this activity will be the training and maintenance of expertise of UK personnel in the use of FEL facilities in preparation for the forthcoming Fourth Generation Light Source (4GLS) at Daresbury. The overall scientific objective is to resolve key issues related to spin manipulation (spin lifetime and spin relaxation). The programme will work closely with two partner institutions, Imperial College and QinetiQ (Malvern), who will provide a focused systematic set of NGS QW structures from parallel funded activities.