  The ability to manipulate plasmons is driving new developments in
electronics, optics, sensing, energy, and medicine. Despite the massive
momentum of experimental research in this direction, a predictive
quantum-mechanical framework for describing electron-plasmon interactions in
real materials is still missing. Here, starting from a many-body Green's
function approach, we develop an ab initio approach for investigating
electron-plasmon coupling in solids. As a first demonstration of this
methodology, we show that electron-plasmon scattering is the primary mechanism
for the cooling of hot carriers in doped silicon, it is key to explain measured
electron mobilities at high doping, and it leads to a quantum zero-point
renormalization of the band gap in agreement with experiment.
