Synchronous Spatial Oscillation of Electron- and Mn-Spin Polarizations in Dilute-Magnetic-Semiconductor Quantum Wells under Spin-Orbit Effective Magnetic Fields

摘要

In semiconductors, spin-orbit effective magnetic fields, i.e., the Rashba andDresselhaus fields, are used to control electron-spin polarization. Thisoperation, however, destroys the electron-spin coherence, and the spinpolarization is limited to the vicinity of a ferromagnetic source electrode. Inthis paper, we propose the use of dilute magnetic semiconductors to improve thecoherence of spatially oscillating electron-spin polarization. In dilutemagnetic semiconductors, the electron-spin polarization near the sourceelectrode dynamically induces the local spin polarization of magneticimpurities through s-d spin-flip scattering. This impurity-spin polarizationimproves, in turn, the coherence of the electron-spin polarization, and thisimproved electron-spin polarization induces impurity-spin polarization fartherin the adjacent region. Because of this positive feedback, the coherent andsynchronized spatial oscillations of electron- and impurity-spin polarizationsgrow cooperatively. A numerical calculation for a CdMnTe quantum welldemonstrates the validity of this mechanism.