Two-Photon Resonant Raman Scattering in Red-HgI₂

Abstract

The two-photon resonant Raman scattering (TRRS) process via the excitonic molecule (EM) state in red-HgI₂ is studied at 1.6 K. The intensity of the TRRS line is enhanced with FWHM 0.7 meV at 2.3324 eV which corresponds to a half of the EM energy. From the analysis of the TRRS data, the dispersion curve of the transverse exciton polariton is determined: The transverse exciton energy and its effective mass relative to the electron rest mass are obtained as 2.3348±0.0001 eV and 1.3±0.1, respectively. The background dielectric constant, ε_∞ is determined to be 10.5±0.5 from the Fabry-Perot interference fringes of a thin single crystal.