Theory of the resistive transition in overdoped Tl2Ba2CuO6+δ:: Implications for the vortex viscosity and the quasiparticle scattering rate in high-Tc superconductors

We show that recent measurements of the magnetic field dependence of the magnetization, specific heat and resistivity of overdoped T-c similar to 17 K Tl2Ba2CuO6+delta in the vicinity of the superconducting H-c2 imply that the vortex viscosity is anomalously small and that the material studied is inhomogeneous with small (a few hundred angstroms), regions in which the local T-c is much higher than the bulk T-c. The anomalously small vortex viscosity can be derived from a microscopic model in which the quasiparticle lifetime varies dramatically around the Fermi surface, being small everywhere except along the zone diagonal ("cold spot"). We propose experimental tests of our results. [S0031-9007(98)06441-2].