Inelastic light scattering on coupled plasmon-LO phonon modes in high magnetic fields

Abstract

We report on the results of high-magnetic-field (up to 28T) inelastic light scattering measurements of coupled plasmon–phonon modes in metallic GaAs samples with electron concentrations ranging from 1017 to 2×1018cm−3. The zero-field Raman spectra of the investigated samples show peaks related to the transverse optical phonon (TO) as well as the coupled plasmon–phonon ω− (below TO frequency) and ω+ (above LO frequency) modes. In the backscattering Voigt geometry (k⊥B) in which the modes propagating across the field direction are probed, the magnetic field does not influence the TO resonance but leads to a splitting of both ω+ and ω− branches. The experimental data are approximated using the dielectric function formalism. For a highly doped sample, the interaction between coupled plasmon–phonon modes with the Bernstein mode is observed.