Searching for dark matter with a spin-based interferometer

Nat. Commun. 16, 4953 (2025) · DOI: 10.1038/s41467-025-60178-6 · arXiv: 2408.02668

License: CC BY 4.0.

Abstract

Axion-like particles (ALPs) arise from well-motivated extensions to the Standard Model and could account for dark matter. ALP dark matter would manifest as a field oscillating at an (as of yet) unknown frequency. The frequency depends linearly on the ALP mass and plausibly ranges from 10−22 to 10 eV/c2. This motivates broadband search approaches. We report on a direct search for ALP dark matter with an interferometer composed of two atomic K-Rb-3He comagnetometers, one situated in Mainz, Germany, and the other in Kraków, Poland. We leverage the anticipated spatio-temporal coherence properties of the ALP field and probe all ALP-gradient-spin interactions covering a mass range of nine orders of magnitude. No significant evidence of an ALP signal is found. We thus place new upper limits on the ALP-neutron, ALP-proton and ALP-electron couplings reaching below gaNN < 10−9 GeV−1, gaPP < 10−7 GeV−1 and gaee < 10−6 GeV−1, respectively. These limits improve upon previous laboratory constraints for neutron and proton couplings by up to three orders of magnitude.

Figures

12 panels with data across 8 figures. Each panel page shows the plot, its columns and its files; each data.csv begins with a header naming the paper, the panel, the source, the license and the provenance route.

Fig. 1

Illustrative figure, no extractable data. Shown in the paper PDF.

Fig. 2

The underlying data is not available. The figure is shown in the paper PDF.

Fig. 3

• panel (1): Histogram of the measured noise, p.d.f. against the normalized combined Fourier amplitude $|A^{K+M}(\omega)/\Delta A^{K+M}(\omega)|$, for the frequency bins between $\omega_E$ and 0.01 Hz. A blue vertical line marks the bin at $\omega_E$, drawn as a downward arrow in the print, and the red dashed line is the local 95% detection threshold. data.csv

Fig. 4

• panel (1): Mean upper limit on the ALP-neutron coupling $g_{aNN}$ ($\mathrm{GeV}^{-1}$) against ALP mass $m_a$ ($\mathrm{eV}/c^2$) on log-log axes, labelled This work, with the region it excludes shaded. The printed panel's reference constraints (laboratory, solid, and astrophysical, dashed) are not drawn. data.csv

Fig. 5

• panel (1): Mean upper limit on the ALP-proton coupling $g_{aPP}$ ($\mathrm{GeV}^{-1}$) against ALP mass $m_a$ ($\mathrm{eV}/c^2$) on log-log axes, labelled This work, with the region it excludes shaded. The printed panel's reference constraints (laboratory, solid, and astrophysical, dashed) are not drawn. data.csv

Fig. 6

• panel (1): Mean upper limit on the ALP-electron coupling $g_{aee}$ ($\mathrm{GeV}^{-1}$) against ALP mass $m_a$ ($\mathrm{eV}/c^2$) on log-log axes for a fully shielded comagnetometer, labelled This work, with the region it excludes shaded. The printed panel's laboratory and astrophysical reference constraints are not drawn. data.csv

Fig. 7

• panel (2): DC calibration factor (a.u.) of the Mainz (red) and Kraków (blue) comagnetometers against day of 2024, where the print labels calendar dates. Bottom plot of the printed figure. The hosted panel has 42 Mainz and 25 Kraków points against the 40 and 28 fits of the printed legend. data.csv

Fig. 8

• panel (1): Histogram of the normalized signal estimator, counts against $S(\omega)/\mathrm{fit}(\omega)$ on a logarithmic count axis, with the fitted non-central $\chi^2$ distribution (orange) and the 95% global-significance threshold (red dashed line). data.csv

Fig. 9

• panel (1): Probability density (p.d.f.) of the signal amplitude, magnetic field (fT), at a frequency bin near 11.1 mHz for an inserted effective coupling $g_{\mathrm{eff}}=0\;\mathrm{GeV}^{-1}$, with the 95% detection threshold as a red dashed line. The top of the three stacked histograms of the printed figure. data.csv
• panel (2): Probability density (p.d.f.) of the signal amplitude, magnetic field (fT), at a frequency bin near 11.1 mHz for an inserted effective coupling $g_{\mathrm{eff}}=2.3\times10^{-8}\;\mathrm{GeV}^{-1}$, with the 95% detection threshold as a red dashed line. The middle of the three stacked histograms of the printed figure. data.csv
• panel (3): Probability density (p.d.f.) of the signal amplitude, magnetic field (fT), at a frequency bin near 11.1 mHz for an inserted effective coupling $g_{\mathrm{eff}}=4.54\times10^{-8}\;\mathrm{GeV}^{-1}$, with the 95% detection threshold as a red dashed line. The bottom of the three stacked histograms of the printed figure. data.csv

Fig. 10

• panel (1): $95\%$ C.L. $\kappa(\omega_a,\phi_x,\phi_y)$ against frequency $f$ (Hz) on a logarithmic axis, with a black dashed line at $\kappa = 1$. The left plot of the printed figure. data.csv
• panel (2): Mainz comagnetometer frequency response, amplitude (arb. units) against frequency $f$ (Hz) on log-log axes: the neutron coupling (solid) and the electron coupling unshielded (dashed), 50% shielded (dotted) and fully shielded (dash-dotted). The top right plot of the printed figure. data.csv
• panel (3): Kraków comagnetometer frequency response, amplitude (arb. units) against frequency $f$ (Hz) on log-log axes: the neutron coupling (solid) and the electron coupling unshielded (dashed), 50% shielded (dotted) and fully shielded (dash-dotted). The bottom right plot of the printed figure. data.csv

Cite

Daniel Gavilan-Martin et al. (11 authors). Searching for dark matter with a spin-based interferometer. Nat. Commun. 16, 4953 (2025). https://doi.org/10.1038/s41467-025-60178-6

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