Spin interactions between conduction electrons and local moments in semiconductor quantum wells.

摘要

Spin interactions are studied between conduction band electrons in GaAs heterostructures and local moments, specifically the spins of constituent lattice nuclei and of partially filled electronic shells of impurity atoms. Nuclear spin polarizations are addressed through the contact hyperfine interaction resulting in the development of a method for high-field optically detected nuclear magnetic resonance sensitive to 108 nuclei. This interaction is then used to generate nuclear spin polarization profiles within a single parabolic quantum well; the position of these nanometer-scale sheets of polarized nuclei can be shifted along the growth direction using an externally applied electric field. In doped Ga1-xMn xAs/Al0.4Ga0.6As quantum wells with 0.002% x 0.13%, measurements of coherent electron spin dynamics show an antiferromagnetic exchange between s-like conduction band electrons and electrons localized in the d-shell of the Mn2+ impurities, which varies as a function of well width. During the course of these investigations, a wide variety of heterostructures are used to confine and control the spin of band electrons. Asymmetric coupled quantum wells have particularly interesting consequences for the spin dynamics of conduction electrons confined therein.