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Universal sheet resistance and revised phase diagram of the cuprate high-temperature superconductors

Upon introducing charge carriers into the copper-oxygen sheets of the enigmatic lamellar cuprates the ground state evolves from an insulator to a superconductor, and eventually to a seemingly conventional metal (a Fermi liquid). Much has remained elusive about the nature of this evolution and about the peculiar metallic state at intermediate hole-carrier concentrations (p). The planar resistivity of this unconventional metal exhibits a linear temperature dependence (ρ∝T) that is disrupted upon cooling toward the superconducting state by the opening of a partial gap (the pseudogap) on the Fermi surface. Here we first demonstrate for the quintessential compound HgBa2CuO4+δ a dramatic switch from linear to purely quadratic (Fermi-liquid-like, ρ∝T2) resistive behavior in the pseudogap regime. Despite the considerable variation in crystal structures and disorder among different compounds, our result together with prior work gives new insight into the p-T phase diagram and reveals the fundamental resistance per copper-oxygen sheet in both linear (ρ=A1T) and quadratic (ρ=A2T2) regimes, with A1 ∝ A2 ∝ 1/p. Theoretical models can now be benchmarked against this remarkably simple universal behavior. Deviations from this underlying behavior can be expected to lead to new insights into the non-universal features exhibited by certain compounds.

cuprates; superconductivty; resistivity; phase diagram

Rad je djelomicno sufinanciran od prokjekta The UKF project (65/10) “New electronic states driven by frustration in layered materials”.