Mahan excitons in Weyl semimetals

We report on a theoretical study of excitons in weakly doped Weyl semimetals. Solving a two-body Coulomb problem in the presence of a monopole Berry vector potential, we obtain the binding energies of electron-hole pairs and establish their dependence on the monopole charge and on the sign of the magnetic quantum number. We discuss the implications of our results for optical absorption experiments.