Localization and interaction of indirect excitons in GaAs coupled quantum wells (original) (raw)
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We report on the principle and realization of a new trap for excitons -the diamond electrostatic trap -which uses a single electrode to create a confining potential for excitons. We also create elevated diamond traps which permit evaporative cooling of the exciton gas. We observe collection of excitons towards the trap center with increasing exciton density. This effect is due to screening of disorder in the trap by the excitons. As a result, the diamond trap behaves as a smooth parabolic potential which realizes a cold and dense exciton gas at the trap center. PACS numbers: 73.63.Hs, 78.67.De
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We report on the kinetics of a low-temperature gas of indirect excitons in the optically-induced exciton trap. The excitons in the region of laser excitation are found to rapidly -within 4 ns -cool to the lattice temperature T = 1.4 K, while the excitons at the trap center are found to be coldessentially at the lattice temperature -even during the excitation pulse. The loading time of excitons to the trap center is found to be about 40 ns, longer than the cooling time yet shorter than the lifetime of the indirect excitons. The observed time hierarchy is favorable for creating a dense and cold exciton gas in optically-induced traps and for in situ control of the gas by varying the excitation profile in space and time before the excitons recombine.
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Physical Review B, 1988
The photoluminescence spectra from a number of high-quality GaAs single-quantum-well samples grown by molecular-beam epitaxy reveal a doublet emission having an energy separation of-1.25 meV. A similar doublet was observed in a sample for which the interrupted growth technique was used. Using excitation-intensity-dependent luminescence and time-resolved spectroscopy,~e will show that the lower-energy components of these doublets have diN'erent origins in di6'erent samples and can be attributed either to biexcitons or to impurity-bound excitons. Using low-temperature photoluminescence (PL) from a number of high-quality GaAs multiple-quantum-well samples grown by molecular-beam epitaxy (MBE), Miller and co-workers'2 first reported a double peak whose splitting was-1 meV. The high-energy peak was attributed to the n 1 heavy-hole-free-exciton transition. Based on the excitation intensity, temperature, and polarization dependencies of the lower-energy peak, they concluded that this transition was due to biexcitons with a binding
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