Study of pseudo gap formation in YBa2(Cu0.995Zn0.005)(3)O-7 - B-2u phonon,NMR and in-plane resistivity measurements

The c-axis polarized B-2u phonon, the NMR relaxation rate and the electrica l resistivity have been measured to study the Zn-doping effects on the temp erature (T) dependence of the pseudo gap or the fluctuating singlet pairs i n the normal state of optimally carrier-doped YBa2Cu3O7. No evidence has be en found that the T-range where the fluctuating singlets are appreciable, i s extended by the Zn-doping, whereas it has been reported that the T-range where a so-called resonance peak in the magnetic excitation spectra of YBa2 Cu3O7 can be observed, is significantly extended by the Zn-doping far above its super conducting transition temperature. Arguments to understand these puzzling results are presented. (C) 2000 Elsevier science Ltd. All rights reserved.