All-electron dark matter-electron scattering with random-phase approximation dielectric screening and local field effects

TL;DR

This paper develops an all-electron computational framework incorporating RPA dielectric screening with local field effects to accurately predict dark matter-electron scattering rates in solids, highlighting the importance of microscopic electronic inhomogeneities.

Contribution

It introduces an all-electron RPA-based method including local field effects for dark matter-electron scattering, with applications to multiple materials and open-source implementation.

Findings

Local field effects significantly influence scattering rates at large momentum transfers.

Dielectric screening with local field effects alters electron recoil spectra.

Systematic comparison of target materials using the developed RPA dielectric functions.

Abstract

Accurate predictions for dark matter-electron scattering in solids require an all-electron treatment together with a faithful description of dielectric screening beyond simple approximations. In particular, local field effects, arising from microscopic inhomogeneities of the electronic response, can significantly modify scattering rates across relevant momentum and energy scales. We present an all-electron framework for computing dark matter-electron scattering rates that incorporates dielectric screening at the random-phase approximation (RPA) level, including local field effects. Using crystalline silicon as a benchmark, we show that local field effects play an important role both at large momentum transfers, spanning multiple Brillouin zones, and at low momentum near the plasmon resonance. We compute electron recoil spectra and projected sensitivities for non-relativistic halo dark matter and for boosted dark matter or other dark-sector particles, which are sensitive to the impact of local field effects in these high and low momentum regimes, respectively. We further present RPA dielectric functions including local field effects for Ge, GaAs, SiC, and diamond, enabling a systematic comparison across target materials. These developments are implemented in the open source code QCDark2.