Far-infrared sphere resonance in a polar semiconductor: A magneto-optical study of InSb particles.

Abstract

The far-infrared response of small InSb particles embedded in a Teflon host has been measured in the frequency range between 5 and 50 ${\mathrm{cm}}^{\mathrm{\ensuremath{-}}1}$. The main feature in this interval is a sphere resonance at 16 ${\mathrm{cm}}^{\mathrm{\ensuremath{-}}1}$ due to the conduction electrons in the particles. With the application of a magnetic field ranging from 0 to 6 T in the Faraday geometry, the InSb-sphere resonance splits into two absorption lines, corresponding to right and left circularly polarized light, respectively. To explain the strength and frequency dependence of these features, the dielectric function of InSb is described by the Drude model and the dielectric function of the composite by the Maxwell-Garnett theory. From the magnetic-field dependence of the resonance frequencies and strengths, three quantities are determined: the dc dielectric-constant contribution from the interband transitions and the concentration and effective mass of the conduction electrons. The spectral line shapes observed in the experiment are well explained by inhomogeneous line broadening due to a variation in carrier concentration between particles.