Nuclear spin polarization in InSb detected by spin-flip Raman gain spectroscopy

Abstract

The conduction electron spin resonance (CESR) in n-type InSb is shifted by the spin polarization of the nuclear and electron spins (Overhauser shift). The authors measured this shift by optically detecting the magnetic CESR using coherent spin-flip Raman scattering of two CO lasers in the infrared region. This method is very useful for studying the hyperfine interaction in narrow-gap semiconductors with high effective g-factors. By using a combined CESR/NMR technique, the effective g-factor in InSb was determined at different magnetic fields with the high precision available from NMR experiments. The Overhauser shift is directly proportional to the probability mod Psi (0) mod 2 of finding an electron at the nuclear site of the 115In or the 121Sb isotope, respectively. In thermal equilibrium, when the spin polarization of the nuclei is known, measurements of the Overhauser shift directly yield information on mod Psi (0) mod 2 of the conduction electrons at the respective nuclear site. Observing the shift while either building up dynamic nuclear polarization or studying the relaxation of the nuclei from high spin polarization to thermal equilibrium yields information on the nuclear spin-lattice relaxation time T1 of each of the isotopes.