Optical studies of the a-, b-, and c-axis charge dynamics in YBa2Cu3O6+x

S. L. Cooper, D. Reznik, A. Kotz, M. A. Karlow, R. Liu, M. V. Klein, W. C. Lee, J. Giapintzakis, D. M. Ginsberg, B. W. Veal, A. P. Paulikas

Research output: Contribution to journalArticlepeer-review


Optical and Raman-scattering studies of a-, b-, and c-axis YBa2Cu3O6+x between 0.025 and 5.5 eV are presented as a function of doping, and compared to the results of Bi2Sr2CaCu2O8 and La2-xSrxCuO4. Our doping-dependence studies show that the redistribution of spectral weight in the CuO2 planes of YBa2Cu3O6+x differs significantly from that seen in La2-xSrxCuO4. We also find that the redistribution of spectral weight in the cuprates is primarily responsible for the loss of two-magnon Raman-scattering intensity with doping. Finally, we show that bound-carrier contributions comprise a significantly larger fraction of the spectral weight below 1 eV in lower-Tc cuprates such as the 2:1:4 compounds than in higher-Tc cuprates such as YBa2Cu3O6+x and Bi2Sr2CaCu2O8. We suggest that the low-frequency conductivity (<1 eV) in the 2:1:4 compounds is most appropriately described by a two-component picture, while that in YBa2Cu3O6+x and Bi2Sr2CaCu2O8 is adequately described as a single component of strongly interacting carriers. In the metallic phase we find several interesting consequences of a single-component interpretation of the optical data in YBa2Cu3O6+x, such as a linear-in-ω frequency-dependent scattering rate and an increase in the interaction strength with decreased carrier density. Finally, we show that the c-axis optical response in YBa2Cu3O7 (Tc∼90 K) is characterized by a c-axis polarized Raman continuum and a Drude conductivity arising from interbilayer charge transport along the c direction. With decreased doping, the c-axis Drude response decreases dramatically, indicating a decoupling of the CuO2 plane bilayers in YBa2Cu3O6+x. By comparison, the ab-plane optical response is not strongly influenced by interbilayer decoupling, suggesting that the unusual ab-plane charge dynamics in YBa2Cu3O6+x persist in nearly isolated CuO2 plane bilayers.

Original languageEnglish (US)
Pages (from-to)8233-8248
Number of pages16
JournalPhysical Review B
Issue number13
StatePublished - 1993

ASJC Scopus subject areas

  • Condensed Matter Physics


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