Metallic c-axis Transport Across Insulating Planes in PrBa₂Cu₄O₈

抄録

We report measurements of the resistivity ρ(T) of high-quality single crystals of PrBa₂Cu₄O₈ along all three principal axes. Substitution of Pr for Y in YBa₂Cu₄O₈ completely suppresses superconductivity through localisation of the in-plane charge carriers. At low temperatures, however, ρ(T) is found to be metallic, ρ(T) ∼ T² for all three crystallographic directions, and is highly one-dimensional (in-plane anisotropy ρ_a/ρ_b ∼ 1000). These results reveal that the CuO double chain network forms a highly anisotropic Fermi liquid ground state at low T. Furthermore, the observation of metallic c-axis resistivity in PrBa₂Cu₄O₈, in the absence of mobile carriers on the planes, confirms that c-axis transport in Y-based cuprates is dominated by the chain carriers.