Describing the Migdal effect with a bremsstrahlung-like process and many-body effects

Recent theoretical studies have suggested that the suddenly recoiled atom struck by dark matter (DM) particle is much more likely to excite or lose its electrons than expected. Such Migdal effect provides a new avenue for exploring sub-GeV DM particles. There been various attempts describe in liquids and semiconductor targets. In this paper we incorporate treatment of bremsstrahlung process electronic many-body effects give full description bulk targets diamond silicon. Compared with results obtained atom-centered localized Wannier functions (WFs) under framework tight-binding (TB) approximation, method proposed study yields larger event rates low energy regime, due $\omega^{-4}$ scaling. We also find photon mediating Coulomb interaction between ion electron-hole pair equivalent exchange single phonon.