  Interlayer excitons in layered materials constitute a novel platform to study
many-body phenomena arising from long-range interactions between quantum
particles. The ability to localise individual interlayer excitons in potential
energy traps is a key step towards simulating Hubbard physics in artificial
lattices. Here, we demonstrate spatial localisation of long-lived interlayer
excitons in a strongly confining trap array using a WS$_{2}$/WSe$_{2}$
heterostructure on a nanopatterned substrate. We detect long-lived interlayer
excitons with lifetime approaching 0.2 ms and show that their confinement
results in a reduced lifetime in the microsecond range and stronger emission
rate with sustained optical selection rules. The combination of a permanent
dipole moment, spatial confinement and long lifetime places interlayer excitons
in a regime that satisfies one of the requirements for observing long-range
dynamics in an optically resolvable trap lattice.
