Negative exciton mass in ZnCdSe/ZnSSe superlattices observed by excitonic polariton Raman scattering

Abstract

Resonant Raman scattering of excitonic polaritons at LO phonons in ZnCdSe/ZnSSe superlattices at room temperature reveals strong spatial dispersion effects near the transverse excitonic resonance frequency . For incident photon energies below , the LO phonon anti-Stokes frequency shifts exceed the Stokes shifts, while the inverse relation holds above . All experimental results can be well described in the excitonic polariton formalism in terms of exciton branches with positive and negative excitonic masses above and below , respectively, and an additional damping parameter.

Wave Vectors of Excitonic Polaritons in ZnCdSe/ZnSSe Superlattices Determined by Resonant Raman Scattering

“…In the present paper, we extend the previous work [2] by a scheme to determine the wave vectors of the excitonic polaritons from the phonon wave vectors used in ref. [2].…”

“…In the energy range near w T , strong spatial dispersion effects have recently been observed in room temperature resonant Raman scattering via excitonic polaritons from LO phonons in ZnCdSe/ ZnSSe superlattices [2]. ZnSe-like LO anti-Stokes frequency shifts were found to exceed the Stokes shifts for w i below w T , while the relation is inversed above w T .…”