  Indirect excitons (IXs) in van der Waals transition-metal dichalcogenide
(TMD) heterostructures are characterized by a high binding energy making them
stable at room temperature and giving the opportunity for exploring fundamental
phenomena in excitonic systems and developing excitonic devices operational at
high temperatures. We present the observation of IXs at room temperature in van
der Waals TMD heterostructures based on monolayers of MoS$_2$ separated by
atomically thin hexagonal boron nitride. The IXs realized in the TMD
heterostructure have lifetimes orders of magnitude longer than lifetimes of
direct excitons in single-layer TMD, and their energy is gate controlled.
