Phonon-mediated Migdal effect in semiconductor detectors

TL;DR

This paper introduces a phonon-based framework to describe the Migdal effect in semiconductors, enabling improved detection sensitivity for sub-GeV dark matter particles below tens of MeV.

Contribution

It develops a novel phonon-mediated model for the Migdal effect in semiconductors, extending detection capabilities to lower dark matter masses.

Findings

Effective sensitivity to MeV-scale dark matter is achieved.

The phonon-based approach overcomes limitations of previous methods.

The framework enhances the potential of semiconductor detectors in dark matter searches.

Abstract

The Migdal effect inside detectors provides a new possibility of probing the sub-GeV dark matter (DM) particles. While there has been well-established methods treating the Migdal effect in isolated atoms, a coherent and complete description of the valence electrons in semiconductor is still absent. The bremstrahlung-like approach is a promising attempt, but it turns invalid for DM masses below a few tens of MeV. In this paper, we lay out a framework where phonon is chosen as an effective degree of freedom to describe the Migdal effect in semiconductors. In this picture, a valence electron is excited to the conduction state via exchange of a virtual phonon, accompanied by a multi-phonon process triggered by an incident DM particle. Under the incoherent approximation, it turns out that this approach can effectively push the sensitivities of the semiconductor targets further down to the MeV DM mass region.