Exciton transport and degenerate four wave mixing in topologically disordered systems

Abstract

The static and dynamical properties of excitons in a lattice with a random distribution of polarizable atoms are studied using Green's function techniques. Exciton transport is related to the configurationally averaged particle-hole Green's function which is calculated using the ladder diagram approximation. Degenerate four wave mixing (D4WM) using resonant pump beams and an off resonant probe is shown to provide a direct probe for exciton transport. A disorder induced extra resonance is predicted whose width is proportional to the exciton diffusion coefficient. Numerical calculations are presented for the diffusion coefficient and the D4WM signal as the excitation energy is tuned across the exciton band. © 1993 American Institute of Physics.