Resonant Raman Scattering and Hot Luminescence at the Indirect Exciton in BiI₃

Abstract

Secondary emission (SE) spectra under excitation around the indirect exciton edge of BiI₃ crystals are studied at liquid helium temperatures (LHeT). The spectra consist of one-phonon non-resonant Raman scattering lines, and two-and multi-phonon resonant Raman scattering (RRS) lines associated with hot luminescence (HL) bands due to phonon assisted exciton recombinations. Detailed results on excitation-energy and temperature dependences of the spectra are presented. The RRS cross sections are analyzed on the basis of exciton damping processes near the exciton band bottom, and the HL line shapes are discussed on quasi-thermal equilibrium distribution under the same relaxation mechanisms.