A number of direct detection experiments are searching for electron excitations created by scattering of sub-GeV dark matter. We present an alternate formulation of dark matter-electron scattering in terms of the dielectric response of a material. For dark matter which couples to electrons, this approach automatically accounts for in-medium screening effects, which were not included in previous rate calculations for semiconductor targets. We show that the screening effects appear for both scalar and vector mediators. The result is a non-negligible reduction of reach for direct detection experiments which use dielectric materials as targets. We also explore different determinations of the dielectric response, including first-principles density functional theory (DFT) calculations and a data-driven analytic approximation using a Mermin oscillator model.
@article{arxiv.2101.08275,
title = {Dark matter-electron scattering in dielectrics},
author = {Simon Knapen and Jonathan Kozaczuk and Tongyan Lin},
journal= {arXiv preprint arXiv:2101.08275},
year = {2021}
}