Electronic Raman scattering in optimally doped Tl-2201

We present polarized Raman spectra of nearly optimally doped single crystals of Tl2Ba2CuO6 (Tc=80K and 90K). The peak positions in the B1g component of the electronic Raman scattering are found at 460cm−1 (T c =90K), or 430cm−1 (T c =80K) which corresponds to 2Δ max /κ B T C =7.6 ± 0.4. The A1g - and B2g -symmetry components show smaller values for the peak positions and decrease linearly inw toward lower frequencies while the B1g scattering component shows a decrease cubic inw. The temperature dependence of the B1g scattering component reveals a deviation from BCS behavior. Experimental data are explained on the basis of a dx 2−y2-wave symmetry of the order parameter.