Article abstract
Nature Physics 3, 865 - 871 (2007)
Published online: 28 October 2007 | doi:10.1038/nphys753
Subject Categories: Condensed-matter physics | Materials physics
Quasiparticle interference and superconducting gap in Ca2-xNaxCuO2Cl2
T. Hanaguri1,2, Y. Kohsaka3, J. C. Davis3,4, C. Lupien5, I. Yamada6, M. Azuma6, M. Takano6, K. Ohishi7, M. Ono1,2 & H. Takagi1,2,8
Abstract
High-transition-temperature (high-Tc) superconductivity is ubiquitous in the cuprates containing CuO2 planes, but each cuprate has its own character. The study of the material dependence of the d-wave superconducting gap (SG) should provide important insights into the mechanism of high-Tc superconductivity. However, because of the 'pseudogap' phenomenon, it is often unclear whether the energy gaps observed by spectroscopic techniques really represent the SG. Here, we use scanning tunnelling spectroscopy to image nearly optimally doped Ca2-xNaxCuO2Cl2(Na-CCOC) with Tc=25–28 K. It enables us to observe the quasiparticle interference effect in this material, through which we obtain unambiguous information on the SG. Our analysis of quasiparticle interference in Na-CCOC reveals that the SG dispersion near the gap node is almost identical to that of Bi2Sr2CaCu2Oy (Bi2212) at the same doping level, despite the Tc of Bi2212 being three times higher than that of Na-CCOC. We also find that the SG in Na-CCOC is confined in narrower energy and momentum ranges than Bi2212, which explains—at least in part—the remarkable material dependence of Tc.
- Magnetic Materials Laboratory, RIKEN (The Institute of Physical and Chemical Research), Wako 351-0198, Japan
- CREST, Japan Science and Technology Agency, Kawaguchi 332-0012, Japan
- LASSP, Department of Physics, Cornell University, Ithaca, New York 14853, USA
- CMPMS Department, Brookhaven National Laboratory, Upton, New York 11973, USA
- Département de Physique, Université de Sherbrooke, Sherbrooke, QC J1K 2R1, Canada
- Institute for Chemical Research, Kyoto University, Uji 601-0011, Japan
- Advanced Science Research Center, Japan Atomic Energy Agency, Ibaraki 319-1195, Japan
- Department of Advanced Materials, University of Tokyo, Kashiwa 277-8561, Japan
Correspondence to: T. Hanaguri1,2 e-mail: hanaguri@riken.jp
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