Atomic-Scale Quantitative Analysis of Lattice Distortions at Interfaces of Two-Dimensionally Sr-Doped La(2)CuO(4) Superlattices

[Image: see text] 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 La(2)CuO(4) superlattices, in which single LaO planes are periodically replaced by SrO planes. As shown previously, such structures show T(c) 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 CuO(6) 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).