Dipolar interactions enhanced by two-dimensional dielectric screening in few-layer van der Waals structures

We theoretically examined how the dielectric screening of two-dimensional (2D) layered materials affects the dipolar interaction between interlayer excitons (IXs) in few-layer van der Waals structures. Our analysis indicates that the dipolar interaction is largely enhanced by 2D 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 IX. 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.