Extended spatial coherence of interlayer excitons in van der Waals heterostructures

We report on the spatial and temporal coherence of interlayer exciton ensembles as photoexcited in MoSe2/WSe2 heterostructures and characterized by point-inversion Michelson-Morley interferometry.(1) Below 10 K, the measured spatial coherence length of the interlayer excitons reaches values equivalent to the lateral expansion of the exciton ensembles. In this regime, the light emission of the excitons turns out to be homogeneously broadened in energy with a high temporal coherence. At higher temperatures, both the spatial and temporal coherence lengths decrease, most likely because of thermal processes. The presented findings point towards a spatially extended, coherent many-body state of interlayer excitons at low temperature.