Coherent Superposition of Electric- and Magnetic-Dipole Spin-Flip Transitions in Zinc Blende Semiconductors

摘要

Spin resonance (SR) studies offer an important and unique opportunity for investigating coherent superposition of electric- and magnetic-dipole spin-flip transitions in semiconductors. We will focus on far-infrared studies of conduction-electron spin-flip transitions in narrow-gap semiconductors, where this effect is most clearly evident. Although the SR transition is normally electric-dipole-forbidden, it is well known that there exist mechanisms (e.g., "non-parabolicity" and inversion asymmetry) that relax these selection rules. In comparing the relative importance of these mechanisms, it will be shown that the combination of spin-orbit coupling and inversion asymmetry (as developed by E. I. Rashba and V. I. Sheka) is the dominant process allowing electric-dipole-mduced spin-flip transitions. In this review, special attention will be given to the interference of the electric- and magnetic-dipole matrix ele-ments, which provide a unique opportunity for determining the inversion-asymmetry parameter (including its sign) in zinc blende narrow-gap semiconductors. This effect can also serve as a basis for observing spin-based electromagnetically induced transparency-a phenomenon of considerable contemporary interest from both fundamental and applied viewpoints.