10 June 1996 Electronic Raman scattering as a function of doping in high-Tc superconductors
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We report the results of Raman scattering from the electronic continuum in Bi2Sr2CaCu2O8+(delta ) (Bi 2212) and Tl2Ba2CuO6+(delta ) (Tl 2201) high temperature superconductors with variations in the oxygen content, (delta) . Below Tc, a peak develops in the Raman continuum associated with the opening of a superconducting gap, (Delta) (k). By selecting the polarizations of incident and scattered light, we are sensitive to possible anisotropy of the gap within the a-b plane. Near optimal doping, both materials show gap anisotropy, with 2(Delta) /kBTc values of 7.2 (B1g) vs. 5.8 (A1g) in Tl 2201 and 8.5 (B1g) vs. 6.2 (A1g) in Bi 2212. In contrast, both show an isotropic gap at much lower energy shifts when the carrier concentration is raised: 2(Delta) /kBTc equals 3.9 (5.5) for Tl 2201 (Bi 2212) with Tc equals 37 K (57 K). We compare the observed spectra with calculations based on order parameters with d-wave as well as isotropic s-wave symmetry and conclude that raising the doping level reduces the gap anisotropy to near zero.
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Chris A. Kendziora, Chris A. Kendziora, Ronald J. Kelley, Ronald J. Kelley, Marshall Onellion, Marshall Onellion, } "Electronic Raman scattering as a function of doping in high-Tc superconductors", Proc. SPIE 2696, Spectroscopic Studies of Superconductors, (10 June 1996); doi: 10.1117/12.241776; https://doi.org/10.1117/12.241776

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