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 Title: Interlayer optical response of yttrium barium (copper (cobalt, zinc)) oxide Author(s): Karlow, Marvin Anthony Doctoral Committee Chair(s): Wolfe, J.P. Department / Program: Physics Discipline: Physics Degree Granting Institution: University of Illinois at Urbana-Champaign Degree: Ph.D. Genre: Dissertation Subject(s): Physics, Condensed Matter Abstract: We report optical reflectance and spectroscopic ellipsometry measurements of the in- and out-of-plane dielectric responses of chain substituted $\rm YBa\sb2Cu\sb3O\sb{6 + x}$ and $\rm YBa\sb2(Cu\sb{1 - y}Co\sb{y})\sb3O\sb{6 + x}$ and of plane substituted $\rm YBa\sb2(Cu\sb{1 - y}Zn\sb{y})\sb3O\sb{6 + x}.$ A dramatic decrease in the low-frequency c-axis optical conductivity, $\sigma\sb{\rm c}(\omega),$ is observed with either O reduction or Co substitution, suggesting that structural changes in the Cu(1)-O(4)-Cu(2) complex between the CuO$\sb2$ bilayers dominate the doping dependence of interlayer coupling in $\rm YBa\sb2(Cu\sb{1 - y}M\sb{y})\sb3O\sb{6 + x}$ (M = Co, Zn). The slight decrease in $\sigma\sb{\rm c}(\omega)$ observed with Zn substitution suggests that the charge dynamics in the CuO$\sb2$ planes play at best a minor role in regulating interlayer hopping. We find that the electronic component of the c-axis optical conductivity in $\rm YBa\sb2Cu\sb3O\sb{6 + x}$ is roughly constant below 800 cm$\sp{-1}$, and is well fit over the frequency range 800 cm$\rm\sp{-1} \le\omega\le3200\ cm\sp{-1}$ by $\sigma\sb{\rm c}(\omega)\propto\omega\sp\gamma\ (0 \le\gamma<1.2),$ for all oxygen concentrations $\rm 0.26 \le x \le 0.93.$ The consequences of these results for theories of c-axis transport in the cuprates are discussed. Absorption bands near 0.95 and 2.7 eV in $\sigma\sb{\rm c}(\omega)$ are assigned to plane-to-chain antibonding band transitions, while the c-axis polarized 1.7 eV absorption is attributed to charge transfer transitions between O and Cu atoms in adjacent CuO$\sb2$ planes of a bilayer. We consider the proposed connection between the pseudogap in the c-axis optical conductivity, and the deviations from linearity in the in- and out-of-plane resistivity, and discuss the possibility that either interlayer dynamic disorder or low-q spin scattering may account for these unusual features. Notably, c-axis polarized electronic Raman scattering measurements are discussed that provide evidence for a specific incoherent contribution to $\sigma\sb{c}(\omega)$ resulting from optical phonon assisted interlayer hopping. Issue Date: 1996 Type: Text Language: English URI: http://hdl.handle.net/2142/19570 ISBN: 9780591087970 Rights Information: Copyright 1996 Karlow, Marvin Anthony Date Available in IDEALS: 2011-05-07 Identifier in Online Catalog: AAI9702554 OCLC Identifier: (UMI)AAI9702554
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