title: Spin polaron theory for the photoemission spectra of layered cobaltates.
abstract: Recently, strong reduction of the quasiparticle peaks and pronounced incoherent structures have been observed in the photoemission spectra of layered cobaltates. Surprisingly, these many-body effects are found to increase near the band-insulator regime. We explain these unexpected observations in terms of a novel spin-polaron model for CoO2 planes, which is based on a fact of the spin-state quasidegeneracy of Co3+ ions in oxides. Scattering of the photoholes on spin-state fluctuations suppresses their coherent motion. The observed "peak-dip-hump" type line shapes are well reproduced by the theory.
authors.affiliation: Max-Planck-Institut für Festkörperforschung, Heisenbergstrasse 1, D-70569 Stuttgart, Germany.
authors.forename: Jirí
authors.initials: J
authors.lastname: Chaloupka
authors.forename: Giniyat
authors.initials: G
authors.lastname: Khaliullin