Transition from Casimir to van der Waals force between macroscopic bodies

TL;DR

This study investigates the transition from van der Waals to Casimir forces between gold surfaces using atomic force microscopy, confirming theoretical predictions and estimating the Hamaker constant with good agreement.

Contribution

It provides experimental evidence of the force transition point and validates theoretical models including roughness corrections for macroscopic gold surfaces.

Findings

Transition occurs at about 10% of plasma wavelength

Hamaker constant estimates agree with Lifshitz theory

Force measurements align with theoretical predictions

Abstract

The transition of van der Waals to Casimir forces between macroscopic gold surfaces is investigated by Atomic Force Microscopy in the plane-sphere geometry. It was found that the transition appears to take place at separations about 10 % the plasma wavelength for evaporated gold surfaces, which compares to theoretical predictions by incorporation of experimental optical data and roughness corrections. Moreover, the force data allow estimation of the Hamaker constant AH in the van der Waals regime, which is in good agreement with the Lifshitz theory predictions (even if roughness corrections are taken into account) and former surface force apparatus measurements.