Electron-spinuclear-spin Interactions And Nmr In Semiconductors

摘要

The electron-spinuclear-spin interactions in semiconductors are summarized by putting emphasis on dynamical nuclear-spin polarization and detection achieved by using electrical means. These have been demonstrated in quantum dots in the spin-blockade regime, edge channel in the integer quantum-Hall-effect regime and bulk in the fractional quantum-Hall-effect regime. The electron-spinuclear-spin interactions, especially at the spin transition point of v = 2/3 fractional filling, result in an almost linear relationship between nuclear-spin magnetization and the resistance value. As the nuclear-spin magnetization can be measured for a single layer and even for nanostructures by just measuring the resistance, the powerful features of nuclear magnetic resonance can be successfully applied to semiconductor quantum wells, bilayers and point-contact structures where characteristics are well controlled by gates. In GaAs point-contact devices, full coherent control of a quantum four-level system has been demonstrated for / = 3/2 As and Ga nuclei toward nuclear-spin-based quantum information processing. Multiple quantum coherence was clearly observed reflecting the direct detection of nuclear-spin magnetization. In quantum wells and bilayer systems, novel electron-spin features, such as spin texture, a canted spin state and related low-frequency spin fluctuations arising from the breakdown of planar symmetry, have been sensitively detected by using nuclear-spin-based measurements. We also discuss electron-spin fluctuations originating from spin-orbit interactions observed via a nuclear relaxation experiment and the characterization of the nanoscale strain obtained through quadrupolar splitting. Finally, a possible extension of nuclear-spin manipulation and nuclear-spin-based measurements is briefly discussed.