Anomalously large gap anisotropy in the<i>a</i>-<i>b</i>plane of<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mrow><mml:msub><mml:mrow><mml:mi mathvariant="normal">Bi</mml:mi></mml:mrow><mml:mrow><mml:mn>2</mml:mn></mml:mrow></mml:msub></mml:mrow></mml:math><mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mrow><mml:msub><mml:mrow><mml:mi mathvariant="normal">Sr</mml:mi></mml:mrow><mml:mrow><mml:mn>2</mml:mn></mml:mrow></mml:msub></mml:mrow></mml:math><mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mrow><mml:msub><mml:mrow><mml:mi mathvariant="normal">CaCu</mml:mi></mml:mrow><mml:mrow><mml:mn>2</mml:mn></mml:mrow></mml:msub></mml:mrow></mml:math><mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mrow><mml:msub><mml:mrow><mml:mi mathvariant="normal">O</mml:mi></mml:mrow><mml:mrow><mml:mn>8</mml:mn><mml:mo>+</mml:mo><mml:mi mathvariant="normal">δ</mml:mi></mml:mrow></mml:msub></mml:mrow></mml:math>

Zhi‐Xun Shen(Los Alamos National Laboratory), D. S. Dessau(Los Alamos National Laboratory), B. O. Wells(Stanford University), David M. King(Stanford Synchrotron Radiation Lightsource), W. E. Spicer(Los Alamos National Laboratory), A. J. Arko(Stanford University), D. S. Marshall(Stanford University), L. W. Lombardo(Los Alamos National Laboratory), A. Kapitulnik(Los Alamos National Laboratory), P. H. Dickinson(Stanford University), Sebastian Doniach(Stanford University), J. DiCarlo(Stanford Synchrotron Radiation Lightsource), T. Loeser(Stanford Synchrotron Radiation Lightsource), C. H. Park(Los Alamos National Laboratory)
Physical Review Letters
March 8, 1993
10.1103/physrevlett.70.1553
Cited by 880

Abstract

Superconducting gap anisotropy at least an order of magnitude larger than that of the conventional superconductors has been observed in the a-b plane of ${\mathrm{Bi}}_{2}$${\mathrm{Sr}}_{2}$${\mathrm{CaCu}}_{2}$${\mathrm{O}}_{8+\mathrm{\ensuremath{\delta}}}$ in angle-resolved photoemission spectroscopy. For samples with ${\mathit{T}}_{\mathit{c}}$ of 88 K, the gap size reaches a maximum of approximately 20 meV along the Cu-O bond direction, and a minimum of much smaller or vanishing magnitude 45\ifmmode^\circ\else\textdegree\fi{} away. The experimental data are discussed within the context of various theoretical models. In particular, a detailed comparison with what is expected from a superconductor with a ${\mathit{d}}_{\mathit{x}}^{2}$-${\mathit{y}}^{2}$ order parameter is carried out, yielding a consistent picture.

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