Exploring Low-Mass Dark Matter and Neutrinos with Germanium-Based Quantum Sensors

We present GeQuLEP (Germanium-based Quantum Sensors for Low-Energy Physics), a cryogenic (~4 K) detection platform that couples high-purity Ge (HPGe) to engineered phononic-crystal cavities (PnCCs) and RF-QPC readout for ultra-low-threshold phonon sensing. Strain- and field-defined dipole states form natural quantum dots inside the PnCC, enabling single–primary-phonon sensitivity with target quanta down to 7.45 meV. Within this framework we model both nuclear and electronic recoils, compute primary-phonon detection efficiency as a function of recoil energy, and derive projected event rates over a broad parameter space. The resulting reach indicates sensitivity to sub-MeV/c2 dark matter scattering and prospects for real-time solar pp neutrino detection. By combining phonon engineering, low dissipation, and RF reflectometry, GeQuLEP delineates a path toward scalable, background-sparse sensors for rare-event physics, with performance anchored in device-level models (threshold, bandwidth, and coupling) and systematics-aware rate calculations.