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Spatial homogeneity and doping dependence of quasiparticle tunneling spectra in cuprate superconductors

Yeh, N.-C. and Chen, C.-T. and Hammerl, G. and Mannhart, J. and Tajima, S. and Yoshida, K. and Schmehl, A. and Schneider, C. W. and Schulz, R. R. (2001) Spatial homogeneity and doping dependence of quasiparticle tunneling spectra in cuprate superconductors. Physica C, 364-36 . pp. 450-457. ISSN 0921-4534.

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Scanning tunneling spectroscopy (STS) studies reveal long-range (similar to 100 nm) spatial homogeneity in optimally and underdoped superconducting YBa2Cu3O7-delta (YBCO) single crystals and thin films, and macroscopic spatial modulations in overdoped (Y0.7Ca0.3)BaCu3O7-delta (Ca-YBCO) epitaxial films. In contrast, STS on an optimally doped YBa2(Cu0.9934Zn0.0026Mg0.004)(3)O-6.9 single crystal exhibits strong spatial modulations and suppression of superconductivity over a microscopic scale near the Zn or Mg impurity sites, and the global pairing potential is also reduced relative to that of optimally doped YBCO, suggesting strong pair-breaking effects of the non-magnetic impurities. The spectral characteristics are consistent with d(x2-y2) pairing symmetry for the optimally and underdoped YBCO, and with (d(x2-y2) + s) for the overdoped Ca-YBCO. The doping-dependent pairing symmetry suggests interesting changes in the superconducting ground state, and is consistent with the presence of nodal quasiparticles for all doping levels. The maximum energy gap Delta (d) is non-monotonic with the doping level, while the (2 Delta (d)/k(B)T(c)) ratio increases with decreasing doping. The similarities and contrasts between the spectra of YBCO and of Bi2Sr2CaCu2O8+x are discussed.

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Yeh, N.-C.0000-0002-1826-419X
Additional Information:© 2001 Elsevier Science B.V. Received January 15, 2001. The work at Caltech was supported by NSF, at Augsburg University by BMBF Grant #13N6918/1, and at SRL by the New Energy and Industrial Technology Development Organization (NEDO).
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Bundesministerium für Bildung und Forschung (BMBF)13N6918/1
New Energy and Industrial Technology Development Organization (NEDO)UNSPECIFIED
Subject Keywords:pairing symmetry, pairing potential, cuprate superconductors, doping dependence, scanning tunneling spectroscopy, quasiparticle spectra, high-temperature superconductors, T-C superconductors, reversal symmetry-breaking, d-wave superconductors, single-crystals, magnetic-impurities, phase fluctuations, raman-scattering, pairing symmetry, surface-states
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Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:891
Deposited By: Tony Diaz
Deposited On:03 Nov 2005
Last Modified:02 Oct 2019 22:37

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