The Crucial of Spin-Fluctuation Phenomena and Quantum Interference Effects in the Phase Diagram of Electron Doped Cuprate Superconductors

The normal-state resistivity has been investigated in infinite layer electron-doped cuprates Sr1-xLaxCuO2±δ thin films. Underdoped samples, which clearly show a metal-to-insulator transition (MIT) at low temperatures, allowed the determination of the fundamental physical mechanism behind the upturn of the resistivity, namely the quantum interference effects (QIEs). Evidence arises that, even though a MIT does not occur in optimal- and over-doped samples, a QIEs-driven insulating phase co-exists with a metallic ones, thus severely affecting the overall transport properties. Such a phase-separation scenario reveals the true nature of the metallic phase of electron-doped cuprates, unambiguously dominated by spin-fluctuation phenomena at any temperatures. Our analysis provides a universal phase-diagram for cuprate superconductors, therefore demonstrating a qualitatively symmetry for both hole- and electron-doped cuprates phase diagram as a function of the charge doping.