Systematic evolution of temperature-dependent resistivity in ${\mathrm{La}}_{2\mathrm{-}\mathit{x}}$${\mathrm{Sr}}_{\mathit{x}}$${\mathrm{CuO}}_4$

The in-plane resistivity (${\mathrm{\rho }}_{\mathit{a}\mathit{b}}$) of ${\mathrm{La}}_{2\mathrm{-}\mathit{x}}$${\mathrm{Sr}}_{\mathit{x}}$${\mathrm{CuO}}_4$ has been studied over a wide temperature (4–1000 K) and composition range (0<x<0.35). The much discussed T-linear resistivity is observed only in the narrow composition region associated with optimal superconductivity. In the underdoped range (x<0.1), we observe first indications of resistivity saturation and analyze the resistivity as indicative of a ‘‘small’’ Fermi surface. In the overdoped range (x>0.2), ${\mathrm{\rho }}_{\mathit{a}\mathit{b}}$ follows a novel power-law dependence, ρ∞${\mathit{T}}^{1.5}$, over the entire temperature range up to 1000 K.