Axion dark matter detection by laser induced fluorescence in rare-earth doped materials

Abstract

We present a detection scheme to search for QCD axion dark matter, that is based on a direct interaction between axions and electrons explicitly predicted by DFSZ axion models. The local axion dark matter field shall drive transitions between Zeeman-split atomic levels separated by the axion rest mass energy m a c 2. Axion-related excitations are then detected with an upconversion scheme involving a pump laser that converts the absorbed axion energy (~hundreds of μeV) to visible or infrared photons, where single photon detection is an established technique. The proposed scheme involves rare-earth ions doped into solid-state crystalline materials, and the optical transitions take place between energy levels of 4f N electron configuration. Beyond discussing theoretical aspects and requirements to achieve a cosmologically relevant sensitivity, especially in terms of spectroscopic material properties, we experimentally investigate backgrounds due to the pump laser at temperatures in the range 1.9 − 4.2 K. Our results rule out excitation of the upper Zeeman component of the ground state by laser-related heating effects, and are of some help in optimizing activated material parameters to suppress the multiphonon-assisted Stokes fluorescence.

New experimental approaches in the search for axion-like particles

“…The Italian collaboration AXIOMA [605] has started feasibility studies to experimentally implement this detection concept. First results involve the exploration of suitable targets involving molecular oxygen [606], or rare-earth ions doped into solid-state crystalline materials [607], as well as the study of possible backgrounds to this detection method.…”

Infrared and visible scintillation of Ho3+-doped YAG and YLF crystals

“…However, at this point of our research, the intrinsic noise of this kind of detector is still too high for any practical applications [5,6]. Although the laser wavelength does not correspond to any pure electronic transitions from the ground state, the laser light can still be absorbed by means of several mechanisms, leading to populate the same level that we would like to be populated only by particle excitation.…”

Linestrength ratio spectroscopy as a new primary thermometer for redefined Kelvin dissemination

“…A possible system useful to extend LRT range towards few Kelvin is a rare-earth-doped crystal. In such materials, the shielding of f electrons by closed shells makes possible optical transitions between these quasi-unperturbed f levels [40] with very narrow achieved linewidths as, for example, the transitions of Erbium doped YLiF 4 ( + Er : YLF 3 ) in the near-IR region [41,42]. For this reason, we propose this crystal as a target specie to perform LRT in the low temperature range of ITS-90.…”