KAPPA-DEPENDENT ELECTRONIC-STRUCTURE, A LARGE GHOST FERMI-SURFACE, AND A PSEUDOGAP IN A LAYERED MAGNETORESISTIVE OXIDE

The k-dependent electronic structure of the low temperature ferromagne tic state of La1.2Sr1.8Mn2O7 was measured using angle-resolved photoem ission spectroscopy and calculated using the local spin density approx imation (LSDA). The measured near-Fermi energy states display E vs k a nd symmetry relationships which agree relatively well with the LSDA pr ediction through much of the Brillouin zone, and the locus of lowest e nergy excitations matches the predicted large Fermi surface quite well . However, the spectral features are too broad to be well described as Fermi-liquid-like quasiparticles, and they are strongly suppressed fr om the Fermi energy, i.e., there is a pseudogap in the excitation spec trum. We discuss the spectral properties in terms of strong coupling t o a local effect such as a lattice distortion.