Searching for scalar dark matter with compact mechanical resonators

TL;DR

This paper investigates the potential of small, high-quality mechanical resonators to detect ultralight scalar dark matter by measuring atomic strain effects on fundamental constants, expanding the search parameter space.

Contribution

It proposes using compact, cryogenically cooled mechanical resonators at kHz to MHz frequencies as novel detectors for scalar dark matter, covering unexplored mass ranges.

Findings

High-Q, cryogenically cooled resonators can access new dark matter parameter space.

Resonators with significantly smaller mass than gravitational wave detectors are effective.

Multiple resonator designs can target a range of dark matter particle masses.

Abstract

We explore the viability of laboratory-scale mechanical resonators as detectors for ultralight scalar dark matter. The signal we investigate is an atomic strain due to modulation of the fine structure constant and the lepton mass at the Compton frequency of dark matter particles. The resulting stress can drive an elastic body with acoustic breathing modes, producing displacements that are accessible with opto- or electromechanical readout techniques. To address the unknown mass of dark matter particles (which determines their Compton frequency), we consider various resonator designs operating at kHz to MHz frequencies, corresponding to $10^{-12}-10^{-5}$ eV particle mass. Current resonant-mass gravitational wave detectors that have been repurposed as dark matter detectors weigh $\sim \! 10^3$ kg. We find that a large unexplored parameter space can be accessed with ultra-high-$Q$, cryogenically-cooled, cm-scale mechanical resonators possessing $\sim \! 10^7$ times smaller mass.