Temperature dependence of electrical resistivity of high-Tc cuprates -   from pseudogap to overdoped regions
  The effects of planar hole concentration, p, and in-plane disorder, Zn (y), on the DC resistivity, r(T), of sintered samples of Y_{1-x}Ca_xBa_2(Cu_{1-y}Zn_y)_3O_{7-d} were investigated over a wide doping range by changing both the oxygen deficiency (d) and Ca content (x). From the r(T,p) data we extracted characteristic crossover temperatures on the underdoped and overdoped sides, T* and T_m respectively, above which r(T) is linear. We compare our results with a number of other polycrystalline, thin film and single crystal cuprate superconductors and find similar behavior in the p-dependence of T*(p), T_m(p), and the resistivity exponent, m(p), in fits to r(T) = r_0 + aT^m on the overdoped side. Our findings point towards the possible existence of a quantum critical point (QCP) at the doping p=0.19 +/- 0.01. 
S.H. Naqib, J.R. Cooper, J.L. Tallon, C. Panagopoulos