biostudies-literatureRoumpos GEngineering and Physical Sciences Research Council6467-72https://www.ebi.ac.uk/biostudies/studies/S-EPMC3340049biostudies-literatureUnknown109(17)We create a large exciton-polariton condensate and employ a Michelson interferometer setup to characterize the short- and long-distance behavior of the first order spatial correlation function. Our experimental results show distinct features of both the two-dimensional and nonequilibrium characters of the condensate. We find that the gaussian short-distance decay is followed by a power-law decay at longer distances, as expected for a two-dimensional condensate. The exponent of the power law is measured in the range 0.9-1.2, larger than is possible in equilibrium. We compare the experimental results to a theoretical model to understand the features required to observe a power law and to clarify the influence of external noise on spatial coherence in nonequilibrium phase transitions. Our results indicate that Berezinskii-Kosterlitz-Thouless-like phase order survives in open-dissipative systems.Proceedings of the National Academy of Sciences of the United States of AmericaPower-law decay of the spatial correlation function in exciton-polariton condensates.PMC3340049GR/S92892/01EP/I031014/1EP/I028900/1GR/S92892/02Roumpos GKeeling JNitsche WHLittlewood PBLohse MSzymanska MHYamamoto YWorschech LLoffler AHofling SForchel AfalsePower-law decay of the spatial correlation function in exciton-polariton condensates.We create a large exciton-polariton condensate and employ a Michelson interferometer setup to characterize the short- and long-distance behavior of the first order spatial correlation function. Our experimental results show distinct features of both the two-dimensional and nonequilibrium characters of the condensate. We find that the gaussian short-distance decay is followed by a power-law decay at longer distances, as expected for a two-dimensional condensate. The exponent of the power law is measured in the range 0.9-1.2, larger than is possible in equilibrium. We compare the experimental results to a theoretical model to understand the features required to observe a power law and to clarify the influence of external noise on spatial coherence in nonequilibrium phase transitions. Our results indicate that Berezinskii-Kosterlitz-Thouless-like phase order survives in open-dissipative systems.2012-01-01T00:00:00Z2012 Apr2021-02-21T09:20:06Z2019-03-27T00:14:15ZS-EPMC33400492249659510.1073/pnas.1107970109