Kelvin probe force microscopy of metallic surfaces used in Casimir force measurements

TL;DR

This study uses Kelvin probe force microscopy to map the electrostatic potential on gold surfaces used in Casimir force experiments, assessing its impact on force measurements and discrepancies.

Contribution

It provides a detailed potential distribution analysis on Au surfaces and evaluates its effect on Casimir force measurements, highlighting limitations of electrostatic corrections.

Findings

Potential distribution does not account for the observed pressure differences.

Calculated electrostatic pressure does not match the measured Casimir pressure discrepancy.

Potential variations are consistent at low pressure, but insufficient to explain measurement deviations.

Abstract

Kelvin probe force microscopy at normal pressure was performed by two different groups on the same Au-coated planar sample used to measure the Casimir interaction in a sphere-plane geometry. The obtained voltage distribution was used to calculate the separation dependence of the electrostatic pressure $P_{\rm res}(D)$ in the configuration of the Casimir experiments. In the calculation it was assumed that the potential distribution in the sphere has the same statistical properties as the measured one, and that there are no correlation effects on the potential distributions due to the presence of the other surface. Within this framework, and assuming that the potential distribution does not vary significantly at low pressure, the calculated $P_{\rm res}(D)$ does not explain the magnitude or the separation dependence of the difference $\Delta P (D)$ between the measured Casimir pressure and the one calculated using a Drude model for the electromagnetic response of Au.