Doping-induced change of optical properties in underdoped cuprate superconductors

1 January 1999

journal article
Published by IOP Publishing in Journal of Physics: Condensed Matter

Vol. 11 (1) , 239-264
https://doi.org/10.1088/0953-8984/11/1/020

Abstract

We report on the ab-plane optical reflectance measurements of single crystals of Y-doped and Pr-doped over a wide frequency range from 80 to (10 meV-5 eV) and at temperatures between 20 and 300 K. Y and Pr doping both decrease the hole concentration in the planes. This has allowed us to investigate the evolution of ab-plane charge dynamics at doping levels ranging from heavily underdoped to nearly optimally doped. Our results of the low-frequency optical conductivity and spectral weight do not show any features associated with the normal-state pseudogap. Instead, one-component analysis for the optical conductivity shows the low-frequency depression in the scattering rate at , signalling entry into the pseudogap state. Alternatively, no clear indications of the normal-state pseudogap are detected in the temperature-dependent zero-frequency free-carrier scattering rate by using two-component analysis. In the superconducting state, there is also no convincing evidence of superconducting gap absorption in all spectra. We find that there is a `universal correlation' between the numbers of carriers and the transition temperature. This correlation holds whether one considers the number of carriers in the superfluid or the total number of carriers.

Keywords

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