Polariton Luminescence in Monoclinic ZnP₂Crystal

Abstract

Exciton polariton luminescence and its temperature dependence have been investigated in monoclinic ZnP 2 crystals. The energies of transverse and longitudinal excitons ( E T and E L ) are determined by a fit of the reflection spectrum to a simple polariton model. In the vicinity of the 1 s exciton, two emission bands are observed at energies E T and E L . They are attributed to the luminescence from lower and upper branch polaritons, respectively. In particular, the lower polariton luminescence band exhibits a well-defined doublet structure at 2 K. Both components are separated from each other by about 1 meV with comparable intensities and the same polarization dependence. With increasing temperature, the higher-energy component decreases rapidly as compared to the lower-energy component. The origin of these emission components is discussed.