Article abstract

Nature Physics 2, 190 - 194 (2006)

Subject Categories: Condensed-matter physics | Materials physics

Angle-resolved phase-sensitive determination of the in-plane gap symmetry in YBa2Cu3O7-delta

J. R. Kirtley1, C. C. Tsuei1, Ariando2, C. J. M. Verwijs2, S. Harkema2 and H. Hilgenkamp2

Understanding the nature of the ground state and its low-lying excitations in the copper oxide superconductors is a prerequisite for determining the origin of high-temperature superconductivity. A superconducting order parameter (that is, the energy gap) with a predominantly dx2-y2 symmetry is well-established. However, various deviations from a pure d-wave pair state, such as the possibility of Cooper pairing with broken time-reversal symmetry or an admixed dx2-y2+s pair state, have been theoretically predicted and actively sought in numerous experimental studies. Here, we present an angle-resolved phase-sensitive technique for accurately determining the in-plane pairing symmetry, and demonstrate this technique in optimally doped YBa2Cu3O7-delta. We find that the gap along the b-axis (Cu–O chain) direction is at least 20% larger than that along the a-axis direction, and that any imaginary idxy, is or ip component must be smaller than a few per cent of the dx2-y2 component of the gap.

  1. IBM Watson Research Center, Route 134 Yorktown Heights, New York 10598, USA
  2. Faculty of Science and Technology and MESA + Institute for Nanotechnology, University of Twente, PO Box 217, 7500 AE Enschede, The Netherlands

Correspondence to: J. R. Kirtley1 e-mail:


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