A Condensed Matter perspective for Dark Matter detection

Dark matter remains a central unresolved problem in physics; direct detection via non-gravitational interactions requires pushing detector thresholds and understanding complex material responses. This thesis develops and validates a multiscale theoretical–computational framework that links microscopic electronic structure and lattice dynamics to experimentally measurable signals in next-generation low-threshold detectors. We derive and implement accurate scattering rates for both nuclear and electronic recoils, and introduce numerical tools to compute ab initio dielectric functions, including algorithmic simplifications for anisotropic materials, using time-dependent density-functional theory and electronic-structure methods. Molecular dynamics and atomistic simulations are combined with electronic calculations to model defect creation, lattice response, and their impact on excitations and charge collection. We apply these methods to realistic detector contexts, including scintillating cryogenic calorimeters, semiconducting targets, and superconducting sensors. The results produce concrete, testable predictions for signal rates and spectral features, quantify how microscopic defects can bias or obscure signals, and offer design guidance to optimize sensitivity to light dark matter. By providing a coherent pathway from first principles to observables, this work improves the fidelity of signal modeling and informs the design and interpretation of future direct-detection experiments.