SSM-ILOPSH · Single spin manipulation in locally oxidized p-type semiconductor heterostructures

Exploring the different relaxation mechanisms leading to spin decoherence and thus the realization of long spin lifetimes in single electron nanodevices is one of the central issues in nowadays spintronics. Although such effects have been widely studied in 2DEG-based nano-constrictions, the possibility of the utilization of stronger correlation phenomena characteristic to valence band holes on the transport properties of confined 2DHG systems has remained still unexplored. Recently it has become possible to C-dope (100) AlGaAs heterostructures for high-mobility 2-dimensional hole gases (2DHG) showing clear signatures of the fractional quantum Hall effect. Such structures lend themselves for the fabrication of quantum wires, quantum point contacts and quantum dots, provided they can be grown close (less than 100 nm) to the sample surface and that stable charging configurations can be obtained. The host institute has pioneered the fabrication of nanostructures with local oxidation of semiconductor heterostructures by using the biased tip of an atomic force microscope (AFM). The host has already demonstrated that oxide lines lead to laterally insulating behavior separating the plane of the 2DHG into various electrically disconnected areas. The proposed project aims to develop novel schemes for determining spin-related material parameters (g-factor, spin-orbit coupling strength) in various AFM lithographically defined 2DHG nanostructures via transport measurements. This is essential in order to explore electron spin dynamics, decoherence and relaxation in quantum dot and double-dot semiconductor spin qubits, and to determine conditions for coherent transfer of spin in nano/micro-circuits as well as methods of detection of spin currents. These experiments help to understand and control the coherent spin states of individual charge carriers, which is fundamental for the field of quantum computation in a solid state environment.