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

TL;DR

This paper demonstrates that using dilute magnetic semiconductors in quantum wells can enhance and synchronize electron- and impurity-spin polarizations through a feedback mechanism, improving spin coherence.

Contribution

It introduces a novel mechanism where impurity-spin polarization enhances electron-spin coherence via positive feedback in dilute magnetic semiconductor quantum wells.

Findings

Numerical simulations confirm synchronized spin oscillations.

Impurity-spin polarization enhances electron-spin coherence.

Positive feedback leads to stable spin oscillations.

Abstract

In semiconductors, spin-orbit effective magnetic fields, i.e., the Rashba and Dresselhaus fields, are used to control electron-spin polarization. This operation, however, destroys the electron-spin coherence, and the spin polarization is limited to the vicinity of a ferromagnetic source electrode. In this paper, we propose the use of dilute magnetic semiconductors to improve the coherence of spatially oscillating electron-spin polarization. In dilute magnetic semiconductors, the electron-spin polarization near the source electrode dynamically induces the local spin polarization of magnetic impurities through s-d spin-flip scattering. This impurity-spin polarization improves, in turn, the coherence of the electron-spin polarization, and this improved electron-spin polarization induces impurity-spin polarization farther in the adjacent region. Because of this positive feedback, the coherent and synchronized spatial oscillations of electron- and impurity-spin polarizations grow cooperatively. A numerical calculation for a CdMnTe quantum well demonstrates the validity of this mechanism.