Optical Detection of Dynamic Polarization of Nuclei in Semiconductors

Much research has been performed by now on optical pumping of spin-polarized electrons in semiconductors [1–6]. In these experiments, the spin-oriented carriers were excited from the valence band into the conduction band by absorption of circularly-polarized light. The most convenient for the detection of the spin orientation of the electrons is an optical method [2, 3] with investigation of the recombination-luminescence polarization. For III–V crystals, the selection rules for interband transitions yield a simple connection S = 0.5 P between the degree of circular polarization of the luminescence ( S ) and the degree of stationary orientation of the electrons ( P ) at the bottom of the conduction band. We have investigated, also by an optical method, a number of effects that arise when the electron spins interact strongly with the magnetic moments of the nuclei in the crystal.