Physics Theory Seminar with Saarik Kalia on Looking for Low-Frequency Dark Matter in the Lab

Dark photons and axions are exciting candidates for dark matter, which may be observable through their coupling to electromagnetism. While many experimental programs have been developed to explore the wide range of parameter space over which these candidates may exist, the mass range corresponding to frequencies below a kHz has been seldom probed by laboratory experiments. In this talk, I will discuss two ongoing efforts to probe this region of parameter space. Both rely on the ability of dark-photon or axion dark matter to source an oscillating magnetic field signal inside an experimental apparatus. In the first case, this magnetic field signal is detected by observing its effect on a magnetically levitated superconductor. The oscillating magnetic field signal sourced by dark matter can drive motion of the superconductor, which becomes resonantly enhanced when the dark matter Compton frequency matches the trapping frequency of the superconductor. As mechanical resonators, magnetically levitated systems are naturally sensitive to lower frequencies, making this a well-suited detector for sub-kHz dark matter candidates. In the second case, we instead consider Earth as the experimental apparatus. That is, we search directly for the oscillating magnetic field signal using unshielded magnetometers located across the Earth's surface. Not only does the signal strength receive an enhancement from the large size of the Earth, but it is also correlated between independent measurements at different locations. I will discuss the search for this signal in existing publicly available magnetometer data maintained by the SuperMAG collaboration, as well as an independent experimental effort, known as SNIPE Hunt, to measure this signal in the field. I will show that both levitated superconductors and unshielded magnetometers have the potential to set the leading laboratory constraints on dark-photon and axion dark matter in the sub-kHz regime.

This lecture was made possible by the William C. Ferguson fund.