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arXiv:1605.06475 · Physical review. B./Physical review. B

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

Daniel Webber, Brian L. Wilmer, Xiao Liu, Margaret Dobrowolska, J. K. Furdyna, Alan D. Bristow, Kimberley C. Hall

Published Oct 31, 2016• 7 citations
arXivHTMLPDF

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.

DOI
10.1103/physrevb.94.155450

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Proceedings of SPIE, the International Society for Optical Engineering/Proceedings of SPIE•Feb 11, 2010•0 citations
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.
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The interplay between disorder and Coulomb interactions ubiquitously affects the properties of condensed matter systems. We examine its role in the nonlinear optical response of semiconductor quantum wells. In particular, we investigate the coherent coupling strength between exciton resonances that are spectrally split by interface fluctuations. Previous studies yielded conflicting results. In light of rising interest in semiconductor devices that rely on spatial and/or temporal coherence, we revisit this problem by applying a newly developed spectroscopy method: electronic two-dimensional Fourier transform spectroscopy (2DFTS). 2DFTS is a powerful technique for revealing the presence of coupling and for distinguishing the (coherent or incoherent) nature of such coupling, especially in complex systems with several spectrally overlapping resonances. Even the most basic information about such complex systems, including the homogeneous and inhomogeneous linewidths of various resonances, cannot be extracted reliably using conventional spectroscopic tools. In these new 2DFTS measurements, we did not observe any clear cross peaks corresponding to coherent couplings between either heavy-hole or light-hole excitons. These measurements allow us to place a quantitative upper bound on the possible coupling strength in this prototypical system. A modified mean-field theory reveals a simple yet important relation that determines how the coherent coupling strength depends on the disorder correlation length and Coulomb interaction length. © 2010 Copyright SPIE - The International Society for Optical Engineering.