Far-Infrared Magnetospectroscopy in Indium-Antimony

Far-infrared (FIR) magnetotransmission in InSb was investigated experimentally and theoretically, with emphasis on intra-Landau level spin flip transitions. The experiments were performed at low temperatures at a series of wavelengths generated by an optically pumped FIR laser. In connection with the spin flip transitions, we have (1) determined that the dominant mechanism which allows electric -dipole spin resonance in InSb is inversion asymmetry; (2) we have determined the anisotropy of the conduction electron g factor in this material; and (3) we have discovered that the behavior of the spin resonance transition depends on the photon momentum (')q. A theoretical analysis of the latter effect reveals that this novel phenomenon arises as a result of interference between the electric-dipole (ED) and magnetic-dipole (MD) terms in the Hamiltonian. EDMD interference has been observed as an inseparable part of the spin resonance spectra of conduction as well as donor -bound electrons. This experiment provides a direct and elegant way to obtain the inversion asymmetry parameter. This EDMD interference bears a close relationship to the so -called "magneto-electric" effect. In addition to the study of spin resonance, we have observed and identified a series of other resonances (combined resonance for both free and donor-bound electrons, cyclotron-resonance harmonics for free electrons, and Fabry -Perot magnetoplasma oscillations), and have concluded that the dominant mechanism allowing the cyclotron-resonance harmonics is the interaction between free electrons and ionized impurities. We have also analyzed the Fabry-Perot oscillations as a self-consistent tool for determining the electron concentration.