Spin polaron theory for the photoemission spectra of layered cobaltates.
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.
Chaloupka
Jirí
J
Max-Planck-Institut für Festkörperforschung, Heisenbergstrasse 1, D-70569 Stuttgart, Germany.
Khaliullin
Giniyat
G