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In page Bose–Einstein condensate:

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Excitons, electron-hole pairs, were predicted to condense at low temperature and high density by Boer et al., in 1961.[citation needed] Bilayer system experiments first demonstrated condensation in 2003, by Hall voltage disappearance.[5] Fast optical exciton creation was used to form condensates in sub-kelvin Cu2O in 2005 on.[citation needed]