ELECTRONIC RAMAN-SCATTERING IN OPTIMALLY DOPED TL-2201

We present polarized Raman spectra of nearly optimally doped single cr ystals of Tl2Ba2CuO6 (T-c = 80K and 90K). The peak positions in the B- 1g component of the electronic Raman scattering are found at 460cm(-1) (T-c = 90K), or 430cm(-1) (T-c = 80K) which corresponds to 2 Delta(ma x)/k(B)T(c) = 7.6 +/- 0.4. The A(1g-) and B-2g-symmetry components sho w smaller values for the peak positions and decrease linearly in omega toward lower frequencies while the B-1g scattering component shows a decrease cubic in omega. The temperature dependence of the B-1g scatte ring component reveals a deviation from BCS behavior. Experimental dat a are explained on the basis of a d(x2-y2)-wave symmetry of the order parameter.