Quantum Mechanical Model Calculations of Phonon Polaritons in Two–Dimensional Crystals11The project supported by National Natural Science Foundation of China through grant No. 68977017 and No. 9687005-01.

Abstract

The properties of the simplest phonon–polaritons exist in a two–dimensional diatomic ionic or polar dielectric are investigated by the quantum field theory methods. We considered the two–dimensional crystal as a simple model of a thin slab, an interface or a heterojunction. The Hamiltonian operator describing the interaction between a photon and the phonon mode of the two–dimensional medium is calculated. Anharmonic effects are neglected. The dispersion curves of the phonon-polaritons and the -dependence of the electric field strength in each polaAton branch are calculated and presented for various cases in a graphical form. It is shown that these properties have close relations with the distribution of the electromagnetic field in the direction.