Influence of image forces on charge–dipole interaction in two-layered systems.

This article investigates the electrostatic interaction between a fixed point charge \( Q \) and a freely rotating point dipole \( P \) located near the planar interface between two insulating media with different dielectric permittivities \(\varepsilon_1\) and \(\varepsilon_2\). It demonstrates that the competition between the charge–dipole interaction and the dipole’s image-force self-energy induced by the dielectric mismatch leads to spatial regions where the dipole can have either one (O1) or two (O2) equilibrium orientations, with complex boundaries that evolve depending on parameters such as the magnitudes of \( Q \) and \( P \), their relative positions, and the dielectric contrast. Analytical expressions for the dipole orientation maps, the O1–O2 boundary profiles, and their parameter-dependent evolution are derived, revealing phenomena such as the emergence of closed O2 or O1 regions and cusped boundaries. The study further predicts the existence of local minima in the total electrostatic dipole energy near the interface, which can act as traps for dipoles—relevant for excitons, trions, polar molecules, and Rydberg states in layered heterostructures—and discusses implications for exciton behavior, charge carrier interactions, and device physics in layered electronic and optoelectronic systems.