Electronic Phase Diagram of High-TcCuprate Superconductors from a Mapping of the In-Plane Resistivity Curvature

We propose that resistivity curvature mapping (RCM) based on the in-plane resistivity data is a useful way to objectively draw electronic phase diagrams of high-T₂ cuprates, where various crossovers are important. In particular, the pseudogap crossover line can be conveniently determined by RCM. We show experimental phase diagrams obtained by RCM for Bi₂Sr₂-ₙLaₙCuO₆+, La₂-ₗSrₗCuO₄, and YBa₂Cu₃Oₘ, and demonstrate the universal nature of the pseudogap crossover. Intriguingly, the electronic crossover near optimum doping depicted by RCM appears to occur rather abruptly, suggesting that the quantum-critical regime, if it exists, must be very narrow.