Ab initio theory of coherent electron-phonon-photon processes in photoemission from single-crystal materials

Perhaps surprisingly, in photoemission from some single-crystal materials, coherent three-body electron-phonon-photon processes can dominate over two-body electron-photon processes. We present a fully ab initio theory of such processes including electron-phonon matrix elements computed using Wannier function techniques and including electron emission process from bulk into vacuum. Our results explain why the momentum spread observed experimentally for photoelectrons from PbTe(111) differs from the expectations of previous theories by over an order of magnitude, and also predict that coherent electron-phonon-photon processes can contribute up to ~60% of the photocurrent from the emitted bulk electrons. Finally, we shall discuss the prospects for incorporating surface photoemission effects through a novel plane-wave Green’s function approach.