The Migdal effect in semiconductors

TL;DR

This paper derives the Migdal effect in semiconductors from dark matter interactions, showing it can enhance detection sensitivity for sub-GeV dark matter due to higher excitation rates compared to atomic targets.

Contribution

It provides the first complete derivation of the Migdal effect in semiconductors, including multiphonon production, and calculates the rate using density functional theory.

Findings

Migdal effect rate is higher in semiconductors than in atoms.

Including the Migdal effect improves dark matter detection sensitivity.

The rate depends on the material's energy loss function.

Abstract

When a nucleus in an atom undergoes a collision, there is a small probability to inelastically excite an electron as a result of the Migdal effect. In this Letter, we present a first complete derivation of the Migdal effect from dark matter-nucleus scattering in semiconductors, which also accounts for multiphonon production. The rate can be expressed in terms of the energy loss function of the material, which we calculate with density functional theory (DFT) methods. Because of the smaller gap for electron excitations, we find that the rate for the Migdal effect is much higher in semiconductors than in atomic targets. Accounting for the Migdal effect in semiconductors can therefore significantly improve the sensitivity of experiments such as DAMIC, SENSEI and SuperCDMS to sub-GeV dark matter.