Plasmon production from dark matter scattering
Jonathan Kozaczuk, Tongyan Lin
Abstract
We present a first calculation of the rate for plasmon production in semiconductors from nuclei recoiling against dark matter. The process is analogous to bremsstrahlung of transverse photon modes, but with a longitudinal plasmon mode emitted instead. For dark matter in the 10 MeV---1 GeV mass range, we find that the plasmon bremsstrahlung rate is 4--5 orders of magnitude smaller than that for elastic scattering, but 4--5 orders of magnitude larger than the transverse bremsstrahlung rate. Because the plasmon can decay into electronic excitations and has characteristic energy given by the plasma frequency ${\ensuremath{\omega}}_{p}$, with ${\ensuremath{\omega}}_{p}\ensuremath{\approx}16\text{ }\text{ }\mathrm{eV}$ in Si crystals, plasmon production provides a new signature and method to detect nuclear recoils from sub-GeV dark matter.