Casimir force calculations near the insulator-conductor transition in gold thin films

TL;DR

This paper theoretically investigates how the Casimir force varies with gold thin film thickness near the insulator-conductor transition, revealing a non-monotonic behavior linked to the percolation threshold.

Contribution

It models the dielectric properties of gold thin films near the transition using the Drude-Smith model, connecting film thickness with Casimir force variations.

Findings

Casimir force decreases with decreasing film thickness until a minimum

Force increases again after the minimum near the percolation threshold

Minimum force coincides with the critical film thickness for percolation

Abstract

We present theoretical calculations of the Casimir force for Au thin films near the insulator-conductor transition that has been observed experimentally. The dielectric function of the Au thin films is described by the Drude-Smith model. The parameters needed to model the dielectric function such as the relaxation time, plasma frequency and the backscattering constant depend on the thickness of the film. The Casimir force decreases as the film thickness decreases until it reaches a minimum after which the force increases again. The minimum of the force coincides with the critical film thickness where a percolation conductor-insulator occurs.