Electronic structure of layered perovskite-relatedSr1−yLayNbO3.5−x

Abstract

The electronic properties and the crystal structure of layered perovskite-related niobates ${\mathrm{Sr}}_{1\ensuremath{-}y}{\mathrm{La}}_{y}{\mathrm{NbO}}_{3.5\ensuremath{-}x}$ can be tuned by gradually changing the oxygen stoichiometry. We have studied the electronic structure of this series in detail by angle-integrated and angle-resolved (ARPES) photoemission and x-ray absorption (NEXAFS) on ${\mathrm{SrNbO}}_{3.45}$ and ${\mathrm{La}}_{0.1}{\mathrm{Sr}}_{0.9}{\mathrm{NbO}}_{3.39}$ single crystals. ARPES shows a one-dimensional dispersion and a purely one-dimensional Fermi surface with a nesting vector ${2k}_{F}=0.56{\mathrm{\AA{}}}^{\ensuremath{-}1}.$ A strongly anisotropic electronic character appears in polarization-dependent O $1s$ NEXAFS as well. Local-density approximation (LDA) band-structure calculations support this dispersion behavior of the lowest-lying conduction band and find additional Fermi surface sheets with a more two-dimensional character.