Resonance Raman study of 2Δ-gap like features in superconducting BI-2212 and YBCO

We studied the variation of the 2Δ-gap like peaks with incident photon energy Ei in two superconducting samples, optimally doped YBCO (Tc=93.6 K) and overdoped Bi-2212 (Tc=82 K). Our results highlight the composite nature of the 2Δ-gap like peaks in the HTS. Below the superconducting Tc we see a redistribution of spectral weight and the appearance of the 2Δ-gap like features. In B1g Raman symmetry these features change their shape, peak position, and intensity with increasing Ei. For Ei∼3.5 eV we find little redistribution, only a strong new peak at a Raman frequency well above the accepted values of twice Δmax.