Resonance Raman study of the superconducting gap and low energy excitations in Tl2Ba2CuO6+delta superconductors

Low energy electronic Raman scattering from Tl2Ba2CuO6+delta Single crystals with T-c = 25 and 85 K has been studied using excitation energies from 1.65 to 3.05 eV. The B-1g 2 Delta peak position shows that the 2 Delta/k(B)T(c) value decreases as the doping level increases. The resonance profiles of the 2 Delta peak and the continuum show similar and strong resonances towards the 3.4 eV optical absorption peak in both crystals, which indicates that (1) the 2 Delta peak and the continuum are coupled to light scattering by the same mechanism, and (2) the light scattering mechanism for both features involves the 3.4 eV optical absorption process.