Fig. 2: Constraints on the coupling parameters Λ_γ and Λ_e as a function of the mass of the field m_ϕ, for scalar field dark matter as in the basic scalar scenario.

Dashed lines represent constraints on the electron coupling Λ_e and dotted lines represent constraints on the photon coupling Λ_γ, at the 95% confidence level. The green region denotes the parameter space excluded in the current study through the spectral analysis of data from the GEO600 gravitational-wave detector. Other coloured regions indicate parameter spaces excluded through previous direct experimental searches: Hees et al.⁶ (blue), Van Tilburg et al.⁵ (yellow), Kennedy et al.⁴⁵ (brown), Aharony et al.³⁸ (magenta), Branca et al.⁴⁰ (purple), Savalle et al.⁸ (cyan) and Antypas et al.³⁹ (red). The black curves and grey regions correspond to previous constraints from ‘fifth-force’ searches/tests of the equivalence principle; to our knowledge, the most stringent such constraints for this dark matter scenario are from the MICROSCOPE experiment^7,43 (lower curves at low mass) and the Cu/Pb torsion pendulum experiment performed by the Eöt-Wash group^26,37,41 (at higher masses).