Signatures of four-particle correlations associated with exciton-carrier interactions in coherent spectroscopy on bulk GaAs

TL;DR

This study uses advanced spectroscopy to analyze four-particle correlations in bulk GaAs, revealing how exciton-carrier interactions influence the material's coherent optical response with detailed simulation insights.

Contribution

It provides new experimental 2DFTS data and theoretical modeling showing the relative strength of exciton-carrier versus exciton-exciton interactions in GaAs.

Findings

Exciton-carrier coupling is about ten times stronger than exciton-exciton coupling.

EID effects are three times more significant than EIS in the coherent response.

Spectroscopy results vary from dispersive to absorptive depending on excitation energy.

Abstract

Transient four-wave mixing studies of bulk GaAs under conditions of broad bandwidth excitation of primarily interband transitions have enabled four-particle correlations tied to degenerate (exciton-exciton) and nondegenerate (exciton-carrier) interactions to be studied. Real two-dimensional Fourier-transform spectroscopy (2DFTS) spectra reveal a complex response at the heavy-hole exciton emission energy that varies with the absorption energy, ranging from dispersive on the diagonal, through absorptive for low-energy interband transitions to dispersive with the opposite sign for interband transitions high above band gap. Simulations using a multilevel model augmented by many-body effects provide excellent agreement with the 2DFTS experiments and indicate that excitation-induced dephasing (EID) and excitation-induced shift (EIS) affect degenerate and nondegenerate interactions equivalently, with stronger exciton-carrier coupling relative to exciton-exciton coupling by approximately an order of magnitude. These simulations also indicate that EID effects are three times stronger than EIS in contributing to the coherent response of the semiconductor.