Search for Screened Interactions Associated with Dark Energy Below the 100 $\mathrm{\mu m}$ Length Scale

TL;DR

This study searches for unknown, screened interactions between mass and forces at sub-100 micrometer scales using a microsphere and cantilever setup, setting new limits on such forces and constraining chameleon dark energy models.

Contribution

It introduces a novel experimental approach to detect screened interactions at microscopic scales and provides the first constraints on chameleon fields in this regime.

Findings

No new interactions detected; consistent with electrostatic backgrounds.

Placed upper limits on force strength below 0.1 fN.

Excluded certain parameter space for chameleon dark energy models.

Abstract

We present the results of a search for unknown interactions that couple to mass between an optically levitated microsphere and a gold-coated silicon cantilever. The scale and geometry of the apparatus enables a search for new forces that appear at distances below 100 $\mu$m and which would have evaded previous searches due to screening mechanisms. The data are consistent with electrostatic backgrounds and place upper limits on the strength of new interactions at $<0.1$ fN in the geometry tested. For the specific example of a chameleon interaction with an inverse power law potential, these results exclude matter couplings $\beta > 5.6 \times 10^4$ in the region of parameter space where the self-coupling $\Lambda \gtrsim 5$ meV and the microspheres are not fully screened.