Searching for dark matter with atomic clocks and laser interferometry

We propose new schemes for the direct detection of low-mass dark matter with atomic clock and laser interferometry experiments. Dark matter, which consists of low-mass bosons, can readily form an oscillating classical field that survives to reside in the observed galactic dark matter haloes if these particles have sufficiently low mass and are sufficiently feebly interacting. We have recently shown that the interaction of an oscillating classical dark matter field φ with Standard Model fields via quadratic-in- φ couplings produces both a `slow' cosmological evolution and oscillating variations in the fundamental constants. Oscillating variations in the fundamental constants produce oscillating shifts in the transition frequencies of atomic clocks and other related systems, which can be used as high-precision probes to search for dark matter. Using recent atomic dysprosium spectroscopy data, we have derived limits on the quadratic interaction of φ with the photon that improve on existing constraints by up to 15 orders of magnitude. We have also proposed the use of laser and maser interferometry, in which a photon wavelength is compared with the interferometer arm length, as a novel high-precision platform to search for dark matter, with effects due to the variation of the electromagnetic fine-structure constant on alterations in the accumulated phase enhanced by up to 13 orders of magnitude.