ab-plane optical properties of Ni-doped Bi2Sr2CaCu2O8+δ

H. L. Liu*, D. B. Tanner, H. Berger, G. Margaritondo

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

7 Citations (Scopus)


The ab-plane optical reflectance of single crystal of Bi2Sr2Ca(Cu1-xNix)2O 8+δ, for x=0.0215, has been measured from 80 to 40000 cm-1 (10 meV-5 eV) and at temperatures between 20 and 300 K. Through Ni substitution, the optical conductivity shows a broad peak at about 400 cm-1, which grows in intensity and shifts to lower frequency as the temperature is reduced. We suggest that this peculiar low-frequency feature is associated with the significant disorder induced by Ni impurities. Analysis of the conductivity within the framework of the two-component and the one-component pictures indicates that the main effect of Ni substitution is to increase impurity scattering rate. There is no evidence of a rapid drop in the free carrier scattering rate near Tc. An estimate of the low-frequency spectral weight shows that Ni reduces the carrier density in the CuO2 plane: each Ni removes one carrier. Below Tc, a sum-rule evaluation finds the superconducting condensate contains about a fifth of the total doping-induced, or two thirds of the free-carrier oscillator strength in the normal state. The strength of the condensate is horizontally offset from the Uemura line, with a smaller superfluid density than implied by Tc. This decreased superfluid density in the CuO2 plane could be connected with the effect of impurity-induced disorder.

Original languageEnglish
Pages (from-to)197-210
Number of pages14
JournalPhysica C: Superconductivity and its applications
Issue number3-4
Publication statusPublished - 1999
Externally publishedYes


  • Infrared spectroscopy
  • Optical reflectivity
  • Superconductor

ASJC Scopus subject areas

  • Electronic, Optical and Magnetic Materials
  • Condensed Matter Physics
  • Energy Engineering and Power Technology
  • Electrical and Electronic Engineering


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