Pseudogap and Superconducting Gap in Y-123: A Raman Study

We present results of electronic Raman-scattering experiments in differently doped Y-123. In B2g symmetry, an analysis of the data in terms of a memory function approach is presented and dynamical relaxation rates $Γ(ω,T)$ and mass-enhancement factors $1+λ(ω,T)$ for the carriers are obtained. Starting from temperatures T > 180K, $Γ(ω,T)$ and $1+λ(ω,T)$ are extrapolated to lower temperatures and used to re-calculate Raman spectra. By comparison with our data, we find a loss of spectral weight between Tc < T < T* at all doping levels x. T* is comparable to the pseudogap temperature found in other experiments. Below Tc, the superconducting gap is observed. It depends on x and scales with Tc whereas the energy scale of the pseudogap remains the same.

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