Collective oscillations driven by correlation in the nonlinear optical regime

TL;DR

This paper investigates how exciton-exciton correlations influence collective oscillations in nonlinear optical systems, revealing ultrafast modes and their dependence on Coulomb interactions through analytical and numerical methods.

Contribution

It introduces a detailed analysis of collective exciton polarization modes considering correlations beyond mean-field, highlighting their impact on ultrafast optical responses.

Findings

Identification of ultrafast collective modes in excitonic systems

Dependence of mode properties on high-frequency correlation functions

Numerical demonstration of collective mode signatures in emission

Abstract

We present an analytical and numerical study of the coherent exciton polarization including exciton-exciton correlation. The time evolution after excitation with ultrashort optical pulses can be divided into a slowly varying polarization component and novel ultrafast collective modes. The frequency and damping of the collective modes are determined by the high-frequency properties of the retarded two-exciton correlation function, which includes Coulomb effects beyond the mean-field approximation. The overall time evolution depends on the low-frequency spectral behavior. The collective mode, well separated from the slower coherent density evolution, manifests itself in the coherent emission of a resonantly excited excitonic system, as demonstrated numerically.