Effect of Monolayer Thickness Fluctuations on Coherent Exciton Coupling   in Single Quantum Wells
  Monolayer fluctuations in the thickness of a semiconductor quantum well (QW) lead to three types of excitons, located in the narrower, average and thicker regions of the QW, which are clearly resolved in optical spectra. Whether or not these excitons are coherently coupled via Coulomb interactions is a long-standing debate. We demonstrate that different types of disorder in QWs distinctly affects the coherent coupling and that the coupling strength can be quantitatively measured using optical two-dimensional Fourier transform spectroscopy. We prove experimentally and theoretically that in narrow quantum wells the coherent coupling occurs predominantly between excitons residing in the disorder-free areas of the QWs and those residing in the plateau-type disorder. In contrast, excitons localized in the fault-type disorder potentials do not coherently couple to other excitons. 
Yuri D. Glinka, Zheng Sun, Mikhail Erementchouk, Michael N.   Leuenberger, Alan D. Bristow, Steven T. Cundiff, Allan S. Brac...
cond-mat.mes-hall quant-ph