Development of Novel Quantum Calorimeters for Rare Event Detection

We present a novel approach for the detection of Coherent Elastic Neutrino-Nucleus Scattering (CEνNS) using PbWO₄ crystals and paramagnetic phonon sensors for low-threshold, low-background athermal phonon sensing. The paramagnetic phonon sensors, consisting of Er-doped Ag metallic films, are directly deposited onto the surfaces of target crystals. Athermal phonons generated by neutrino interactions in the crystal are absorbed by the magnetic films, inducing spin flips that are precisely read out using DC-SQUID (Superconducting Quantum Interference Device) magnetometers. This technique offers strong versatility, enabling reliable integration of magnetic sensing films with a wide range of single-crystal detector materials, including PbWO₄ for CEνNS detection, CaMoO₄ for neutrinoless double beta decay search, and carbon-based crystals for low mass dark matter detection. It features fast timing resolution (<100 ns) for athermal phonon arrival, enhancing precise phonon-pulse shape discrimination (P-PSD) to suppress non-nuclear recoil backgrounds and electronic noise events. Additionally, the method is highly scalable, requiring no complex superconducting circuit fabrication on the detector substrate and relying only on Ag:Er film deposition, which is broadly compatible with many crystal types. We report recent progress from our experimental development, including characterization of PbWO₄ crystals for neutrino detection applications, as well as development of carbon-based crystals for sub-GeV dark matter detection.