Evidence of Doping-Dependent Pairing Symmetry in Cuprate Superconductors

N.-C. Yeh, C.-T. Chen, G. Hammerl, J. Mannhart, A. Schmehl, C. W. Schneider, R. R. Schulz, S. Tajima, K. Yoshida, D. Garrigus, M. Strasik
2001 Physical Review Letters  
Scanning tunneling spectroscopy (STS) studies reveal long-range spatial homogeneity and predominantly d_x^2-y^2-pairing spectral characteristics in under- and optimally doped YBa_2Cu_3O_7-δ superconductors, whereas STS on YBa_2(Cu_0.9934Zn_0.0026Mg_0.004)_3O_6.9 exhibits microscopic spatial modulations and strong scattering near the Zn or Mg impurity sites, together with global suppression of the pairing potential. In contrast, in overdoped (Y_0.7Ca_0.3)Ba_2Cu_3O_7-δ, (d_x^2-y^2+s)-pairing
more » ... y^2+s)-pairing symmetry is found, suggesting significant changes in the superconducting ground-state at a critical doping value.
doi:10.1103/physrevlett.87.087003 pmid:11497973 fatcat:5ulsh7ynhvb4jbyq3pti26lquq