Band structure of the Jahn-Teller polaron from quantum Monte Carlo

A path-integral representation for the Jahn-Teller polaron (JTP) is constru cted. It leads to a perturbation series that can be summed exactly by the d iagrammatic quantum Monte Carlo technique. The groundstate energy, effectiv e mass, spectrum, and density of states of the three-dimensional JTP are ca lculated with no systematic errors. The band structure of JTP is found to b e similar to that of the Holstein polaron. The mass of JTP increases expone ntially with the coupling constant. At small phonon frequencies, the spectr um of JTP is flat at large momenta, which leads to a strongly distorted den sity of states with a massive peak at the top of the band.