Electronic structure measurements of colossal magnetoresistive manganese-oxides: Polaronic effects on the band structure

We have used high energy-resolution angle-resolved photoemission spectrosco py (ARPES) to map the k-dependent electronic structure of single-crystallin e samples of the manganese-based perovskites as a function of doping level, temperature, and layer number. The measured near-Fermi energy states displ ay E vs. k and symmetry relationships which agree relatively well with the LSDA band theory prediction through much of the Brillouin zone, and the loc us of lowest energy excitations matches the predicted large Fermi surface q uite well. However, the spectral features are too broad to be well describe d as Fermi-Liquid like quasiparticles, and they are strongly suppressed fro m the Fermi energy, e.g., there is a pseudogap in the excitation spectrum. We discuss the spectral properties in terms of strong coupling to a local e ffect such as a lattice distortion.