  We theoretically examined how the dielectric screening of two-dimensional
layered materials affects the dipolar interaction between interlayer excitons
in few-layer van der Waals structures. Our analysis indicates that the dipolar
interaction is largely enhanced by two-dimensional dielectric screening at an
inter-exciton separation of several nanometers or larger. The underlying
mechanism can be attributed to the induced-charge densities in layered
materials, which give rise to induced-dipole densities at large distances with
directions parallel to that of the interlayer exciton. The interaction between
quadrupolar excitons in trilayer structures are found to be enhanced even
larger, with a magnitude one to two orders stronger than that without 2D
dielectric screening. The strengths of these dipolar and quadrupolar
interactions can be further tuned by engineering the dielectric environment.
