Searching for dilaton dark matter with atomic clocks

TL;DR

This paper proposes using atomic clocks to detect ultralight dilaton dark matter through tiny oscillations in fundamental constants, extending current searches to higher frequencies and significantly improving sensitivity.

Contribution

It introduces a novel experimental approach with atomic clocks to search for ultralight scalar dark matter, achieving unprecedented sensitivity and exploring new parameter space.

Findings

Can probe scalars lighter than 10^-15 eV

Achieves coupling sensitivity down to 10^-11 times gravity

Potential for 10^4 sensitivity enhancement with future clocks

Abstract

We propose an experiment to search for ultralight scalar dark matter (DM) with dilatonic interactions. Such couplings can arise for the dilaton as well as for moduli and axion-like particles in the presence of CP violation. Ultralight dilaton DM acts as a background field that can cause tiny but coherent oscillations in Standard Model parameters such as the fine structure constant and the proton-electron mass ratio. These minute variations can be detected through precise frequency comparisons of atomic clocks. Our experiment extends current searches for drifts in fundamental constants to the well-motivated high-frequency regime. Our proposed setups can probe scalars lighter than 10^-15 eV with discovery potential of dilatonic couplings as weak as 10^-11 times the strength of gravity, improving current equivalence principle bounds by up to 8 orders of magnitude. We point out potential 10^4 sensitivity enhancements with future optical and nuclear clocks, as well as possible signatures in gravitational wave detectors. Finally, we discuss cosmological constraints and astrophysical hints of ultralight scalar DM, and show they are complimentary to and compatible with the parameter range accessible to our proposed laboratory experiments.