Measurement of the short-range attractive force between Ge plates using a torsion balance

TL;DR

This study measures the short-range attractive force between germanium plates, identifying contributions from the Casimir effect and surface patch potentials, and compares experimental results with theoretical models.

Contribution

It introduces a model for surface patch effects to correct force measurements and compares these with multiple Casimir force models.

Findings

Electrical force contributions are significant at short distances.

Corrected measurements align with several Casimir force models.

Residual forces are consistent with theoretical predictions within experimental uncertainty.

Abstract

We have measured the short-range attractive force between crystalline Ge plates, and found contributions from both the Casimir force and an electrical force possibly generated by surface patch potentials. Using a model of surface patch effects that generates an additional force due to a distance dependence of the apparent contact potential, the electrical force was parameterized using data at distances where the Casimir force is relatively small. Extrapolating this model, to provide a correction to the measured force at distances less than 5 $\mu$m, shows a residual force that is in agreement, within experimental uncertainty, with five models that have been used to calculate the Casimir force.