The important role of electron-phonon scattering in photoemission from PbTe(111)

The state of the art in creating high quality electron beams for particle accelerator applications and next generation ultrafast electron diffractometers involves laser-generated photoemission. In this context, a high quality beam requires that electrons emerge in a single direction with low mean transverse energy (MTE, the kinetic energy of the electrons parallel to the surface). Recent density-functional theory calculations by T. Li and W. A. Schroeder [arXiv:1704.00194v1 [physics.acc-ph] (2017)] suggests that PbTe(111) is expected to produce low-MTE photoelectrons due to its electronic band structure. Based on this suggestion, we measured the distribution of photoelectrons from PbTe(111) and found the MTE to be 2 orders of magnitude larger than expected from the electronic band structure. In this talk, we present many-body photoemission calculations including electron-phonon scattering. Our results are in far better agreement with the experiment and underscore the importance of electron-phonon scattering in photoemission from PbTe(111).