Electronic Structure Measurements of Colossal Magnetoresistive Manganese-Oxides: Polaronic Effects on the Band Structure

Abstract

We have used high energy-resolution angle-resolved photoemission spectroscopy(ARPES) to map the k-dependent electronic structure of single-crystallinesamples of the manganese-based perovskites as a function of doping level, temperature,and layer number. The measured near-Fermi energy states display E vs. kand symmetry relationships which agree relatively well with the LSDA band theoryprediction through much of the Brillouin zone, and the locus of lowest energy excitations matches the predicted large Fermi surface quite well. However, thespectralfeatures are too broad to be well described as Fermi-Liquid likequasiparticles, and they are strongly suppressed from the Fermi energy, e.g., there is apseudogap in the excitation spectrum. We discuss the spectral properties interms of strong coupling to a local effect such as a lattice distortion.