Indirect Excitons and Many-body Interactions in InGaAs Double Quantum Wells

Spatially indirect excitons in semiconductor quantum wells are relevant to basic research and device applications because they exhibit enhanced tunability, delocalized wavefunctions, and potentially longer lifetimes relative to direct excitons. Here we summarize recent studies investigating these intriguing quasiparticles in InGaAs double quantum wells using optical multidimensional coherent spectroscopy (MDCS) and photoluminescence excitation (PLE) spectroscopy. Analyses of the spectra confirm a strong influence of many-body effects, and reveal that excited-state zero-quantum coherences between direct and indirect excitons in the quantum wells dephase faster than the much higher-energy single-quantum coherences between excitonic excited states and ground states. The results suggest an important energy-dependent role of continuum states in mediating system dynamics, and they indicate that dephasing mechanisms are associated with uncorrelated or anticorrelated energy-level fluctuations. In broader context, the results may be relevant to the physics of manufactured devices including quantum cascade lasers, and to transfer efficiency between energy levels in a variety of naturally occurring quantum confined systems.