Directional Detection of Light Dark Matter with Polar Materials

TL;DR

This paper explores the detection of light dark matter using polar materials, leveraging phonon interactions and material anisotropy to identify directional signals and improve detection sensitivity.

Contribution

It introduces a novel detection method employing polar materials and DFT calculations to analyze directional dependence of dark matter interactions, including phonon excitations.

Findings

Directional dependence of DM scattering in sapphire demonstrated.

Potential for daily modulation detection with gram-year exposure.

Effective absorption of dark photon DM in polar materials shown.

Abstract

We consider the direct detection of dark matter (DM) with polar materials, where single production of optical or acoustic phonons gives excellent reach to scattering of sub-MeV DM for both scalar and vector mediators. Using Density Functional Theory (DFT), we calculate the material-specific matrix elements, focusing on GaAs and sapphire, and show that DM scattering in an anisotropic crystal such as sapphire features a strong directional dependence. For example, for a DM candidate with mass 40 keV and relic abundance set by freeze-in, the daily modulation in the interaction rate can be established at 90\% C.L. with a gram-year of exposure. Non-thermal dark photon DM in the meV - eV mass range can also be effectively absorbed in polar materials.