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The a-axis optical conductivity of detwinned ortho-II YBa_2Cu_3O_6.50

J. Hwang·J. Yang·T. Timusk·S. G. Sharapov·J. P. Carbotte·D. A. Bonn·Ruixing Liang·W. N. Hardy
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Abstract

The a-axis optical properties of a detwinned single crystal of YBa_2Cu_3O_6.50 in the ortho II phase (Ortho II Y123, T_c= 59 K) were determined from reflectance data over a wide frequency range (70 - 42 000 cm^-1) for nine temperature values between 28 and 295 K. Above 200 K the spectra are dominated by a broad background of scattering that extends to 1 eV. Below 200 K a shoulder in the reflectance appears and signals the onset of scattering at 400 cm^-1. In this temperature range we also observe a peak in the optical conductivity at 177 cm^-1. Below 59 K, the superconducting transition temperature, the spectra change dramatically with the appearance of the superconducting condensate. Its spectral weight is consistent, to within experimental error, with the Ferrell-Glover-Tinkham (FGT) sum rule. We also compare our data with magnetic neutron scattering on samples from the same source that show a strong resonance at 31 meV. We find that the scattering rates can be modeled as the combined effect of the neutron resonance and a bosonic background in the presence of a density of states with a pseudogap. The model shows that the decreasing amplitude of the neutron resonance with temperature is compensated for by an increasing of the bosonic background yielding a net temperature independent scattering rate at high frequencies. This is in agreement with the experiments.

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J. Hwang, J. Yang, T. Timusk, S. G. Sharapov, J. P. Carbotte, D. A. Bonn, Ruixing Liang, W. N. Hardy. 2005-05-11. The a-axis optical conductivity of detwinned ortho-II YBa_2Cu_3O_6.50. https://doi.org/10.1103/physrevb.73.014508

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