Non-perturbative phenomena in semiconductor four-wave mixing spectra

TL;DR

This paper investigates non-perturbative effects in semiconductor four-wave mixing spectra using an exact solution to a non-linear exciton polarization model, revealing Coulomb interaction-induced spectral features and the limits of perturbative approaches.

Contribution

It introduces an exact solution approach to analyze non-perturbative phenomena in semiconductor four-wave mixing, highlighting Coulomb interaction effects and the transition criteria between perturbative and non-perturbative regimes.

Findings

Coulomb interaction causes exciton peak splitting.

Non-monotonous response at exciton frequency depends on external field.

Transition to non-perturbative regime is governed by parameters inversely related to decay rate.

Abstract

Non-perturbative phenomena in four-wave mixing spectra of semiconductors are studied using the exact solution of a widely used phenomenological non-linear equation of motion of the exciton polarization. It is shown that Coulomb interaction, included in the nonlinearity, leads to two characteristic effects, which are essentially of dynamical origin, -- a split of the exciton peak and a non-monotonous dependence of the response at the exciton frequency on the magnitude of the external field. Relations between the spectral features and the parameters of the system is obtained. It is found that the transition from perturbative to non-perturbative regimes is controlled by parameters inversely proportional to the decay rate. It implies that the condition of low excitation density does not necessarily warrant applicability of the perturbational approach.