Non-Coulombic behavior of electrostatic charge-charge interaction in three-layer heterostructures

Abstract

Electrostatic interaction energy WQ1Q2 between two point charges Q1 and Q2 in a three-layer planar system was calculated on the basis of the Green's function method in the classical electrostatic model with constant dielectric permittivities εi (i=1,2,3) for all constituent media. Two significant particular cases of charge configurations were analyzed in more detail: (i) when the both charges are in the same medium and their perpendicular coordinates are equal, Z1=Z2, and (ii) the charges are located at different interfaces and interact across the slab. It was demonstrated that the WQ1Q2 dependences on the charge-charge distance S and its projection R on the XY plane [S2=R2+(Z1−Z2)2] differ from the classical Coulombic one. This phenomenon occurs due to the appearance of polarization charges at both interfaces, making the problem a many-body one. Numerical calculations demonstrated that both the underscreening and overscreening of the electrostatic charge-charge interaction is possible depending on the charge arrangement and the relationships between εi’s in the layers. The deviations from the Coulomb law were found to be especially large when the dielectric constants of the covers are much larger or much smaller than that in the interlayer.