A review of many-body effects in exciton ensembles in semiconductors is given with the emphasis on two-dimensional systems: structures with single and double quantum wells and with quantum microcavities. The Bose—Einstein condensation effect, an accumulation of a macroscopic number of excitons in the ground state of the system, is discussed. The known prohibition on condensation in low-dimensional systems can be lifted due to the disorder resulting from the chaotic potential. Manifestations of the finite exciton lifetime and, correspondingly, of the nonequilibrium of the excitonic system caused by processes of excitons entering and leaving the condensate state are analyzed. Other collective phases of excitons, namely, two-dimensional crystals of dipolar excitons and an electron-hole liquid, formed as a result of interparticle interactions, are discussed.

Keywords: exciton, Bose—Einstein condensate, superfluidity, disorder, dipolar exciton, exciton polariton PACS: 03.75.Hh, 03.75.Kk, 71.35.−y, 71.35.Lk, 71.36.+c, 72.15.Rn (all) DOI: 10.3367/UFNe.2019.10.038663 URL: https://ufn.ru/en/articles/2020/11/a/ 000613920600001 2-s2.0-85101540805 2020PhyU...63.1051G Citation: Glazov M M, Suris R A "Collective states of excitons in semiconductors" Phys. Usp. 63 1051–1071 (2020) BibTexBibNote ® (generic)BibNote ® (RIS)MedlineRefWorks Received: 14th, August 2019, accepted: 1st, October 2019 Оригинал: Глазов М М, Сурис Р А «Коллективные состояния экситонов в полупроводниках» УФН 190 1121–1142 (2020); DOI: 10.3367/UFNr.2019.10.038663