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Science 1 March 1996:
Vol. 271. no. 5253, pp. 1255 - 1257
DOI: 10.1126/science.271.5253.1255
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Reports

Doping-Induced Change of Superconducting Gap Anisotropy in Bi2Sr2Ca1Cu2O8+delta

R. J. Kelley, C. Quitmann, M. Onellion, * H. Berger, P. Almeras, G. Margaritondo

High-resolution angle-resolved photoemission measurements were performed on single crystals of Bi2Sr2Ca1Cu2O8+delta with different oxygen stoichiometries. The data establish that the gap anisotropy (ratio of the gap along Gamma -M to the gap along Gamma -X) can be reversibly changed from sim 20:1 (optimal or underdoped) to sim 2:1 (overdoped). Differences in sample doping explain the conflicting reports on gap anisotropy in the literature. Possible effects of this change in gap anisotropy on the symmetry of the order parameter are discussed. There remains some ambiguity as to the relation between the order parameter and doping.

R. J. Kelley, C. Quitmann, M. Onellion, Applied Superconductivity Center, University of Wisconsin, Madison, WI 53706, USA.
H. Berger, P. Almeras, G. Margaritondo, Institut de Physique Appliquée, École Polytechnique Fédérale, CH-1015 Lausanne, Switzerland.
* To whom correspondence should be addressed.




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Science. ISSN 0036-8075 (print), 1095-9203 (online)