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Proceedings Paper

Local and global effects of quantum impurities on the quasi particle tunneling spectra of p-type and n-type cuprate superconductors
Author(s): Nai-Chang Yeh; Ching-Tzu Chen; Richard P. Vasquez; Chang Uk Jung; J. Y. Kim; Min-Seok Park; Heon-Jung Kim; Sung-Ik Lee; K. Yoshida; Setsuko Tajima
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Paper Abstract

We report scanning tunneling spectroscopic studies of the effects of quantum impurities on cuprate superconductors. The samples include p-type YBa2Cu3O7-δ single crystals with spinless impurities of Zn2+ and Mg2+ ((Zn,Mg)-YBCO) and n-type infinite-layer system Sr0.9La0.1CuO2 with 1% magnetic Ni2+- or 1% non-magnetic Zn2+-impurities that substitute the Cu2+ in the CuO2 plane. The local effects of spinless impurities on the quasiparticles spectra of (Zn,Mg)-YBCO are analogous to those of Zn-substituted Bi2Sr2CaCu2O8+x, and the global effect is manifested by the suppression of the pairing potential Δd and of the spin excitation energy. In contrast, spectroscopic studies of Sr0.9La0.1CuO2 reveal momentum-independent spectra and superconducting gap Δ , with (2Δ/kBTc) ~ 7 for Tc = 43 K and no pseudogap above Tc. The global response of Sr0.9La0.1CuO2 to quantum impurities is similar to that of s-wave superconductors, being insensitive to small concentrations of spinless impurities (Zn) while showing rapid degradation in Tc with increasing magnetic impurities (Ni). Moreover, the spectra of the Ni-substituted Sr0.9La0.1CuO2 reveal strong electron-hole asymmetry and long-range impurity effects, in contrast to the localized impurity effects in the p-type cuprates, and the introduction of Zn yield no reduction in either Δ or Tc. The physical implications of these findings are discussed.

Paper Details

Date Published: 7 November 2002
PDF: 13 pages
Proc. SPIE 4811, Superconducting and Related Oxides: Physics and Nanoengineering V, (7 November 2002); doi: 10.1117/12.452324
Show Author Affiliations
Nai-Chang Yeh, California Institute of Technology (United States)
Ching-Tzu Chen, California Institute of Technology (United States)
Richard P. Vasquez, Jet Propulsion Lab. (United States)
Chang Uk Jung, Pohang Univ. of Science and Technology (South Korea)
J. Y. Kim, Pohang Univ. of Science and Technology (South Korea)
Min-Seok Park, Pohang Univ. of Science and Technology (South Korea)
Heon-Jung Kim, Pohang Univ. of Science and Technology (South Korea)
Sung-Ik Lee, Pohang Univ. of Science and Technology (South Korea)
K. Yoshida, International Superconductivity Technology Ctr. (Japan)
Setsuko Tajima, International Superconductivity Technology Ctr. (Japan)


Published in SPIE Proceedings Vol. 4811:
Superconducting and Related Oxides: Physics and Nanoengineering V
Ivan Bozovic; Davor Pavuna, Editor(s)

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