Unexpectedly slow two particle decay of ultra-dense excitons in cuprous oxide

•Dense excitons are produced by intense two photon excitation.•Two exciton decay occurs more slowly than expected.•Strong interactions are present among dense excitons in cuprous oxide.

For an ultra-dense exciton gas in cuprous oxide (Cu2O), exciton–exciton interactions are the dominant cause of exciton decay. This study demonstrates that the accepted Auger recombination model overestimates the exciton decay rate following intense two photon excitation. Two exciton decay is relevant to the search for collective quantum behavior of excitons in bulk systems. These results suggest the existence of a new high density regime of exciton behavior.