title: Atomic-Scale Quantitative Analysis of Lattice Distortions at Interfaces of Two-Dimensionally Sr-Doped La2CuO4 Superlattices.
abstract: Using spherical aberration corrected high-resolution and analytical scanning transmission electron microscopy, we have quantitatively studied the lattice distortion and the redistribution of charges in two-dimensionally strontium (Sr)-doped La2CuO4 superlattices, in which single LaO planes are periodically replaced by SrO planes. As shown previously, such structures show Tc up to 35 K as a consequence of local charge accumulation on both sides of the nominal SrO planes position. This is caused by two distinct mechanisms of doping: heterogeneous doping at the downward side of the interface (space-charge effect) and "classical" homogeneous doping at the upward side. The comparative chemical and atomic-structural analyses reveal an interrelation between local CuO6 octahedron distortions, hole spatial distribution, and chemical composition. In particular we observe an anomalous expansion of the apical oxygen-oxygen distance in the heterogeneously doped (space-charge) region, and a substantial shrinkage of the apical oxygen-oxygen distance in the homogeneously doped region. Such findings are interpreted in terms of different Jahn-Teller effects occurring at the two interface sides (downward and upward).
authors.affiliation: Max Planck Institute for Solid State Research , Heisenbergstrasse 1, 70569 Stuttgart, Germany.
authors.forename: Yi
authors.initials: Y
authors.lastname: Wang
authors.affiliation: Max Planck Institute for Solid State Research , Heisenbergstrasse 1, 70569 Stuttgart, Germany.
authors.forename: Federico
authors.initials: F
authors.lastname: Baiutti
authors.affiliation: Max Planck Institute for Solid State Research , Heisenbergstrasse 1, 70569 Stuttgart, Germany.
authors.forename: Giuliano
authors.initials: G
authors.lastname: Gregori
authors.affiliation: Max Planck Institute for Solid State Research , Heisenbergstrasse 1, 70569 Stuttgart, Germany.
authors.forename: Georg
authors.initials: G
authors.lastname: Cristiani
authors.affiliation: Max Planck Institute for Solid State Research , Heisenbergstrasse 1, 70569 Stuttgart, Germany.
authors.forename: Ute
authors.initials: U
authors.lastname: Salzberger
authors.affiliation: Max Planck Institute for Solid State Research , Heisenbergstrasse 1, 70569 Stuttgart, Germany.
authors.forename: Gennady
authors.initials: G
authors.lastname: Logvenov
authors.affiliation: Max Planck Institute for Solid State Research , Heisenbergstrasse 1, 70569 Stuttgart, Germany.
authors.forename: Joachim
authors.initials: J
authors.lastname: Maier
authors.affiliation: Max Planck Institute for Solid State Research , Heisenbergstrasse 1, 70569 Stuttgart, Germany.
authors.forename: Peter A
authors.initials: PA
authors.lastname: van Aken
keywords: CuO6 octahedron distortion; electron energy loss spectroscopy; oxide interface; superconductivity; transmission electron microscopy