Quantum biexcitonic liquid in monoclinic ZnP2 crystals

A phonon-roton dispersion relation is proposed for the elementary excitatio ns of a quantum biexcitonic liquid in semiconductors. The proposed dispersi on relation is used as a starting point for a calculation of the photolumin escence spectrum of the liquid and an analysis of its behavior under variat ion of temperature and density of the biexcitonic liquid. The parameters of the dispersion curve of elementary excitations of the quantum biexcitonic liquid are evaluated by fitting the calculated photoluminescence spectrum t o the experimental spectrum of the biexcitonic liquid of semiconducting bet a -ZnP2 crystals. Experimental studies of how the photoluminescence spectru m of a biexcitonic liquid in beta -ZnP2 depends on the temperature and the intensity of the laser excitation confirm the initial theoretical model. Th e dependence of the temperature of the crystals on the excitation intensity is measured, and for some of the samples an anomalous dependence is found: the temperature of the crystal decreases as the excitation intensity incre ases. This effect is probably a consequence of the giant thermal conductivi ty of the superfluid biexcitonic liquid in beta -ZnP2 crystals. (C) 2001 Am erican Institute of Physics.