Dark Matter Absorption via Electronic Excitations

TL;DR

This paper refines the calculation of bosonic dark matter absorption by electronic excitations, emphasizing the importance of in-medium effects and providing updated detection sensitivity projections for various materials.

Contribution

It clarifies the relation between dark matter and photon absorption, especially for scalar dark matter, and highlights the need for first-principles calculations for accurate detection predictions.

Findings

Absorption rates for vector and pseudoscalar dark matter relate to optical properties.

Scalar dark matter absorption involves different operators, unaffected by in-medium screening.

Updated sensitivity projections for semiconductor and superconductor detectors.

Abstract

We revisit the calculation of bosonic dark matter absorption via electronic excitations. Working in an effective field theory framework and consistently taking into account in-medium effects, we clarify the relation between dark matter and photon absorption. As is well-known, for vector (dark photon) and pseudoscalar (axion-like particle) dark matter, the absorption rates can be simply related to the target material's optical properties. However, this is not the case for scalar dark matter, where the dominant contribution comes from a different operator than the one contributing to photon absorption, which is formally next-to-leading-order and does not suffer from in-medium screening. It is therefore imperative to have reliable first-principles numerical calculations and/or semi-analytic modeling in order to predict the detection rate. We present updated sensitivity projections for semiconductor crystal and superconductor targets for ongoing and proposed direct detection experiments.