Improved limits on the coupling of ultralight bosonic dark matter to photons from optical atomic clock comparisons

TL;DR

This paper uses optical atomic clock comparisons to set new, more stringent limits on the interaction strength between ultralight bosonic dark matter and photons, covering a specific mass range and improving previous bounds significantly.

Contribution

It introduces a novel method of constraining dark matter-photon coupling by analyzing frequency ratios from optical clocks, achieving over an order of magnitude improvement in bounds.

Findings

Enhanced constraints on scalar coupling $d_e$ for dark matter masses $10^{-24}$ to $10^{-17}$ eV/c².

Improved limits on the temporal drift of the fine-structure constant $eta$.

More sensitive bounds on the coupling of ultralight dark matter to photons.

Abstract

We present improved constraints on the coupling of ultralight bosonic dark matter to photons based on long-term measurements of two optical frequency ratios. In these optical clock comparisons, we relate the frequency of the ${}^2S_{1/2} (F=0)\leftrightarrow {}^2F_{7/2} (F=3)$ electric-octupole (E3) transition in $^{171}$Yb$^{+}$ to that of the ${}^2S_{1/2} (F=0)\leftrightarrow \,{}^2D_{3/2} (F=2)$ electric-quadrupole (E2) transition of the same ion, and to that of the ${}^1S_0\leftrightarrow\,{}^3P_0$ transition in $^{87}$Sr. Measurements of the first frequency ratio $\nu_\textrm{E3}/\nu_\textrm{E2}$ are performed via interleaved interrogation of both transitions in a single ion. The comparison of the single-ion clock based on the E3 transition with a strontium optical lattice clock yields the second frequency ratio $\nu_\textrm{E3}/\nu_\textrm{Sr}$. By constraining oscillations of the fine-structure constant $\alpha$ with these measurement results, we improve existing bounds on the scalar coupling $d_e$ of ultralight dark matter to photons for dark matter masses in the range of about $ 10^{-24}-10^{-17}\,\textrm{eV}/c^2$. These results constitute an improvement by more than an order of magnitude over previous investigations for most of this range. We also use the repeated measurements of $\nu_\textrm{E3}/\nu_\textrm{E2}$ to improve existing limits on a linear temporal drift of $\alpha$ and its coupling to gravity.