Electron Raman scattering in Tl2Ba2CuO6+x crystals

It is inferred from the position of the 2Δ peak in the electron light scattering spectra that in a sample with high T _c ≈90 K the ratio 2Δ/T _c is approximately equal to 6 and 7 for different polarizations, while in overdoped samples with T _c ≈40 and 35 K the 2Δ peak is observed only in x′y′ polarization with a substantially lower ratio 2Δ/T _c ≈3.2. With decreasing T _c in Tl₂Ba₂CuO_6+x crystals, a transition occurs from strong to weak coupling; the superconducting gap remains anisotropic at different doping levels. Pis’ma Zh. éksp. Teor. Fiz. 64, No. 11, 760–765 (10 December 1996)