Improved bounds on ultralight scalar dark matter in the radio-frequency range

TL;DR

This paper reports a highly sensitive search for ultralight dark matter oscillations in the radio-frequency range using upgraded optical spectroscopy, setting new bounds on UDM couplings to electrons and photons.

Contribution

The study introduces significantly improved experimental sensitivity and new constraints on ultralight dark matter couplings in the 20 kHz to 100 MHz frequency range.

Findings

No detection of ultralight dark matter oscillations.

Constraints on UDM-electron and UDM-photon couplings exceed previous bounds.

Future experiments could surpass equivalence-principle tests in certain coupling scenarios.

Abstract

We present a search for fundamental constant oscillations in the range $20$~kHz-$100$ MHz, that may arise within models for ultralight dark matter (UDM). Using two independent, significantly upgraded optical-spectroscopy apparatus, we achieve up to $\times$1000 greater sensitivity in the search relative to previous work. We report no observation of UDM and thus constrain respective couplings to electrons and photons within the investigated UDM particle mass range $8\cdot 10^{-11}-4\cdot 10^{-7}$ eV. The constraints significantly exceed previously set bounds, and as we show, may surpass in future experiments those provided by equivalence-principle experiments in a specific case regarding the combination of UDM couplings probed by the latter.