Detection of Light Dark Matter With Optical Phonons in Polar Materials

TL;DR

This paper proposes using polar materials like Gallium Arsenide to detect light dark matter through optical phonons, offering a promising new method for direct detection in the sub-GeV mass range.

Contribution

It introduces the concept of using optical phonons in polar materials for dark matter detection and provides analytical estimates for GaAs's detection capabilities.

Findings

GaAs can detect dark photon absorption effectively.

The method covers the freeze-in benchmark for ultralight dark photons.

GaAs is competitive with existing sub-MeV dark matter detection proposals.

Abstract

We show that polar materials are excellent targets for direct detection of sub-GeV dark matter due to the presence of gapped optical phonons as well as acoustic phonons with high sound speed. We take the example of Gallium Arsenide (GaAs), which has the properties needed for experimental realization, and where many results can be estimated analytically. We find GaAs has excellent reach to dark photon absorption, can completely cover the freeze-in benchmark for scattering via an ultralight dark photon, and is competitive with other proposals to detect sub-MeV dark matter scattering off nuclei.