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Originally published in Science Express on 22 January 2009
Science 13 February 2009:
Vol. 323. no. 5916, pp. 923 - 926
DOI: 10.1126/science.1166138
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Reports

Coherence Factors in a High-Tc Cuprate Probed by Quasi-Particle Scattering Off Vortices

T. Hanaguri,1,2* Y. Kohsaka,1,2 M. Ono,1,2 M. Maltseva,3 P. Coleman,3 I. Yamada,4{dagger} M. Azuma,4 M. Takano,4{ddagger} K. Ohishi,5§ H. Takagi1,6

When electrons pair in a superconductor, quasi-particles develop an acute sensitivity to different types of scattering potential that is described by the appearance of coherence factors in the scattering amplitudes. Although the effects of coherence factors are well established in isotropic superconductors, they are much harder to detect in their anisotropic counterparts, such as high-superconducting-transition-temperature cuprates. We demonstrate an approach that highlights the momentum-dependent coherence factors in Ca2–xNaxCuO2Cl2. We used Fourier-transform scanning tunneling spectroscopy to reveal a magnetic-field dependence in quasi-particle scattering interference patterns that is sensitive to the sign of the anisotropic gap. This result is associated with the d-wave coherence factors and quasi-particle scattering off vortices. Our technique thus provides insights into the nature of electron pairing as well as quasi-particle scattering processes in unconventional superconductors.

1 Magnetic Materials Laboratory, RIKEN Advanced Science Institute, Wako 351-0198, Japan.
2 Core Research for Evolutional Science and Techonology (CREST), Japan Science and Technology Agency, Kawaguchi 332–0012, Japan.
3 Department of Physics and Astronomy, Rutgers University, Piscataway, NJ 08854–8019, USA.
4 Institute for Chemical Research, Kyoto University, Uji 601–0011, Japan.
5 Advanced Science Research Center, Japan Atomic Energy Agency, Ibaraki 319–1195, Japan.
6 Department of Advanced Materials, University of Tokyo, Kashiwa 277–8561, Japan.

{dagger} Present address: Department of Chemistry, Ehime Universiy, Matsuyama 790–8577, Japan.

{ddagger} Present address: Institute for Integrated Cell-Material Sciences, Kyoto University, care of Research Institute for Production Development, Kyoto 606-0805 Japan.

§ Present address: Advanced Meson Science Laboratory, RIKEN, Wishina Center for Accelerator-Based Science, Wako 351-0198, Japan.

* To whom correspondence should be addressed. E-mail: hanaguri{at}riken.jp

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THIS ARTICLE HAS BEEN CITED BY OTHER ARTICLES:
Spectroscopic Fingerprint of Phase-Incoherent Superconductivity in the Underdoped Bi2Sr2CaCu2O8+{delta}.
J. Lee, K. Fujita, A. R. Schmidt, C. K. Kim, H. Eisaki, S. Uchida, and J. C. Davis (2009)
Science 325, 1099-1103
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