Dispersive force between dissimilar materials: geometrical effects

TL;DR

This paper investigates how the dispersive Casimir force between a spherical nanoparticle and a planar substrate varies with material properties and geometry, emphasizing the importance of realistic modeling beyond traditional approximations.

Contribution

It introduces a spectral representation formalism to accurately calculate the dispersive force considering arbitrary dielectric properties and geometrical effects.

Findings

Force depends on plasma frequencies, geometry, and separation distance.

Differences in force arise from material and geometric configurations.

Highlights limitations of Derjaguin and Proximity Theorem Approximations.

Abstract

We calculate the Casimir force or dispersive van der Waals force between a spherical nanoparticle and a planar substrate, both with arbitrary dielectric properties. We show that the force between a sphere and a plane can be calculated through the interacting surface plasmons of the bodies. Using a Spectral Representation formalism, we show that the force of a sphere made of a material A and a plane made of a material B, differ from the case when the sphere is made of B, and the plane is made of A. We found that the difference depends on the plasma frequency of the materials, the geometry, and the distance of separation between sphere and plane. The differences show the importance of the geometry, and make evident the necessity of realistic descriptions of the sphere-plane system beyond the Derjaguin Approximation or Proximity Theorem Approximation.