Supermodulation in the atomic structure of the superconductor Bi2Sr2CaCu2O8+x from ab initio calculations

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

doi:10.1103/PhysRevB.77.220507

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Supermodulation in the atomic structure of the superconductor Bi2Sr2CaCu2O8+x from ab initio calculations

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

DOI 10.1103/PhysRevB.77.220507 · Physical Review B

T1

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Abstract

We present results of density functional theory (DFT) calculation of the structural supermodulation in Bi2Sr2CaCu2O8+x 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 tunneling microscopy (STM) experiments as well. The primary structural modulation affecting the CuO2 plane is found to be a buckling wave of tilted CuO5 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 concomitant planar buckling are directly modulating the superconducting pair interaction.

Source-reported materials — not catalogue approval

Formula	Reported Tc (K)	Pressure (GPa)	Type
Bi2Sr2CaCu2O8+x Archive — visibility unverified Source-occurrence policy only; no material identity or catalogue acceptance is inferred from the formula.	90	Pressure not reported	unknown