Structure of BSCCO supermodulation from ab initio calculations

Y. He; S. Graser; P. J. Hirschfeld; H. -P. Cheng

doi:10.1103/physrevb.77.220507

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arXiv · 0709.0662

Structure of BSCCO supermodulation from ab initio calculations

Y. He·S. Graser·P. J. Hirschfeld·H. -P. Cheng

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Abstract

We present results of density functional theory (DFT) calculation of the structural supermodulation in BSCCO-2212 structure, and show that the supermodulation is indeed a spontaneous symmetry breaking of the nominal crystal symmetry, rather than a phenomenon driven by interstitial O dopants. The structure obtained is in excellent quantitative agreement with recent x-ray studies, and reproduces several qualitative aspects of scanning tunnelling microscopy (STM) experiments as well. The primary structural modulation affecting the CuO_2 plane is found to be a buckling wave of tilted CuO_5 half-octahedra, with maximum tilt angle near the phase of the supermodulation where recent STM experiments have discovered an enhancement of the superconducting gap. We argue that the tilting of the half-octahedra and concommitant planar buckling are directly modulating the superconducting pair interaction.

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Y. He, S. Graser, P. J. Hirschfeld, H. -P. Cheng. 2007-09-05. Structure of BSCCO supermodulation from ab initio calculations. https://doi.org/10.1103/physrevb.77.220507

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