Efficient transport of indirect excitons in a van der Waals heterostructure

Abstract: Exciton transport is fundamental for understanding transport phenomena in bosonic systems and for embracing excitation energy transfer in materials. Spatially indirect excitons (IXs) are composed of electrons and holes in separated layers. Long IX lifetimes allow them to form quantum bosonic states and travel long distances. In this work, we measured IX transport in a MoSe$_2$/WSe$_2$ van der Waals heterostructure by time-resolved photoluminescence imaging. These measurements probe the kinetics of IX cloud expansion and reveal the transport characteristics. We found IX transport with anomalously high diffusivity, orders of magnitude higher than for regular diffusive exciton transport in van der Waals heterostructures. This efficient IX transport agrees with long-range ballistic transport and is consistent with the Bose-Hubbard theory prediction of superfluid in moire superlattices.