Coulomb effects in spatially separated electron and hole layers in coupled quantum wells |
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Authors: | L V Butov A Imamoglu K L Campman A C Gossard |
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Institution: | (1) Department of Electrical and Computer Engineering and Center for Quantized Electronic Structures (QUEST), University of California, Santa Barbara, CA 93106, USA;(2) Institute of Solid State Physics, Russian Academy of Sciences, Chernogolovka, 142432 Moscow oblast, Russia;(3) Department of Physics, University of California, Santa Barbara, CA 93106, USA |
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Abstract: | We report on the (magneto-) optical study of many-body effects in spatially separated electron and hole layers in GaAs/AlxGa1?x As coupled quantum wells (CQWs) at low temperatures (T = 1.4 K) for a broad range of electron-hole (e-h) densities. Coulomb effects were found to result in an enhancement of the indirect (interwell) photoluminescence (PL) energy with increasing the e-h density both for a zero magnetic field and at high fields for all Landau level transitions; this is in contrast to the electron-hole systems in single QWs where the main features are explained by the band-gap renormalization resulting in a reduction of the PL energy. The observed enhancement of the ground state energy of the system of the spatially separated electron and hole layers with increasing the e-h density indicates that the real space condensation to droplets is energetically unfavorable. At high densities of separated electrons and holes, a new direct (intrawell) PL line has been observed: its relative intensity increased both in PL and in absorption (measured by indirect PL excitation) with increasing density; its energy separation from the direct exciton line fits well to the X ? and X + binding energies previously measured in single QWs. The line is therefore attributed to direct multiparticle complexes. |
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