Future CEvNS experiments as probes of lepton unitarity and light-sterile neutrinos

We determine the sensitivities of short-baseline coherent elastic neutrino-nucleus scattering (CE$ u$NS) experiments using a pion decay at rest neutrino source as a probe for nonunitarity in the lepton sector, as expected in low-scale type-I seesaw schemes. We also identify the best configuration for probing light sterile neutrinos at future ton-scale liquid argon CE$ u$NS experiments, estimating the projected sensitivities on the sterile neutrino parameters. Possible experimental setups at the Spallation Neutron Source, Lujan facility and the European Spallation Source are discussed. Provided that systematic uncertainties remain under control, we find that CE$ u$NS experiments will be competitive with oscillation measurements in the long run.