Probing Ultralight Dark Matter at the Mega-Planck Scale with the Thorium Nuclear Clock

TL;DR

This paper demonstrates how the ${}^{229}$Th nuclear clock can be used to set new bounds on ultralight dark matter interactions at scales surpassing the Planck scale, using high-precision nuclear spectroscopy.

Contribution

It introduces a novel ultrasensitive method leveraging the ${}^{229}$Th nuclear transition to probe dark matter couplings at the Mega-Planck scale.

Findings

Set the strongest bounds on dark matter in the mass range $10^{-21}$ to $10^{-19}$ eV.

Probed effective interaction scales exceeding $10^6$ times the Planck scale.

Established ${}^{229}$Th nuclear clock as a leading tool for dark matter detection.

Abstract

Ultralight dark matter is expected to induce oscillations of nuclear parameters. These oscillations are characterized by extremely weak couplings or high suppression scales, with the Planck scale - the characteristic scale of quantum gravity - serving as a natural benchmark. Probing this phenomenon requires systems with exceptional sensitivity to shifts in nuclear energies. The uniquely low-energy nuclear isomeric transition in ${}^{229}$Th provides such sensitivity: it directly probes the nuclear interaction and, owing to a near cancellation between electromagnetic and nuclear contributions, its response to changes in nuclear structure is greatly amplified. We devise and perform a new type of ultrasensitive search for dark matter which uses the precision nuclear spectroscopy at JILA to set the strongest bounds in the mass range $10^{-21}\,{\rm eV} \lesssim m_{\rm DM} \lesssim 10^{-19}\,{\rm eV}$. Our results probe effective interaction scales exceeding $10^6$ times the Planck scale (the Mega-Planck scale) and establish the ${}^{229}$Th system as the leading probe of dark matter couplings to the nuclear sector.