Search for Ultralight Scalar Dark Matter with Atomic Spectroscopy

Area of Science:

• Cosmology
• Particle Physics
• Atomic Physics

Background:

• Ultralight scalar dark matter (DM) candidates may interact with photons via dilatonlike couplings.
• These couplings can induce oscillations in fundamental constants, such as the fine-structure constant (α).
• Atomic systems with near-degenerate energy levels are sensitive probes of such variations.

Purpose of the Study:

• To search for ultralight scalar dark matter by detecting oscillations in the fine-structure constant.
• To establish new experimental limits on dilatonlike photon couplings for dark matter.

Main Methods:

• Utilized atomic spectroscopy of two dysprosium isotopes over a two-year period.
• Analyzed spectral data for coherent oscillations at frequencies below 1 rad/s.
• Searched for signals consistent with dark matter-induced variations in the fine-structure constant.

Main Results:

• No statistically significant signal attributable to dark matter coupling was detected.
• New constraints were placed on dilatonlike photon couplings across a broad mass range.
• For scalar fields constituting all dark matter, limits exceed those from equivalence-principle tests by up to 4 orders of magnitude for masses below 3×10⁻¹⁸ eV.

Conclusions:

• Atomic spectroscopy provides a novel and powerful method for constraining ultralight dark matter.
• The current limits demonstrate the potential of atomic clocks for future, more sensitive dark matter searches.
• An unexplained oscillatory power in a control channel suggests a potential systematic effect requiring further investigation.