Size-consistent quasiparticle representation of nonlinear optical susceptibilities in many-electron systems

Abstract

The optical response of a many‐electron system is calculated by mapping it onto a coupled set of classical oscillators representing the electron–hole pair components of the reduced single‐ electron‐density matrix. This classical representation is rigorously established using a Poisson bracket relation. Expressions for the nonlinear optical susceptibilities obtained using a Green’s‐function solution of the oscillatorequations of motion are used to analyze the size scaling of the off‐resonant response and the resonant structure of the response.