Single-Electron Resolution Phonon-Mediated Detectors: Progress and Applications

Abstract

Many astrophysical observations indicate that nonbaryonic dark matter makes up around 85% of the total mass content of the Universe. The SuperCDMS experiment represents one of many concerted efforts around the world to better understand dark matter by attempting to measure it directly and setting limits on its properties, such as mass and interaction cross section. As SuperCDMS and experiments like it get closer to the neutrino floor, which is the level of cross section sensitivity when the dominant background comes from neutrino interactions, new methods will be required to probe to lower cross section parameter space. Additionally, a paradigm shift to include dark matter models with masses lower than about 1 GeV means that dark matter detectors need ever-better resolution to investigate ever-lower-mass dark matter models. To address these scientific questions, I propose using defect creation to help discriminate potential dark matter signal from backgrounds. Molecular dynamics simulations based on more computationally-intensive time-dependent density functional theory calculations suggest that the anisotropy in defect creation energy threshold in solid-state materials could be used to make directionally-sensitive dark matter detectors. Additionally, defect creation energy loss could be used as a separate handle to discriminate possible signal from electron-recoil backgrounds, which is difficult to do at nuclear recoil energies approaching the threshold displacement energy. Finally, this computational work is in tandem with improvements in low-energy threshold, high-mass semiconductor detectors that could enable dark matter experiments to take advantage of defect creation effects. I present the world's first 100-gram-scale detector with single-electron resolution, which is the first step towards utilizing defect creation effects for dark matter searches.