New magneto-optical anomalies of impurity polarons in InSb at the two LO-phonon region - phonon replica

Abstract

New anomalous features in the magneto-optical spectrum of InSb have been investigated recently at frequencies close to twice the LO-phonon frequency in ref. [1]. From the analysis of the experimental data and theoretical models it was shown that the final state interaction between the second excited Landau level (which is involved in the first harmonic cyclotron resonance (HCR), the first excited Landau level plus one phonon (which is involved in the phonon assisted cyclotron resonance (LOCR) and the 2 LO-phonon level, is mediated by LO phonons via the Fröhlich polaron interaction. Agreement between theory and experiment for both the energy levels and the oscillator strengths at various magnetic fields, was obtained by talking into account the influence of shallow impurities, the spin orbit coupling and the nonparabolicity of the band structure of InSb. In the present paper, the integral equation for the Green's function of the LOCR which was derived but only solved approximately in ref. [1] is solved exactly. The resulting energy levels and their corresponding oscillator strength are calculated. Two additional energy levels appear compared to the approximate solution in ref. [1]. These energy levels are one-phonon replica of the first excited Landau level and the ground state plus one-phonon level as renormalized by the Fröhlich interaction. To identify the detailed energy levels, and their intensities calculated here, advanced experimental techniques of higher resolution than reported hitherto, are necessary.