Coherence, incoherence, and scaling along the c axis of Y Ba 2 Cu 3 O 6 + x

摘要: The optical properties of single crystals YBa2Cu3O6+x have been examined along the c axis above and below critical temperature (Tc) for a wide range oxygen dopings. dependence optically-determined value dc conductivity (σdc) in normal state suggests crossover from incoherent (hopping-type) transport at lower dopings (x < 0.9) to more coherent anisotropic three-dimensional behavior overdoped ≈ 0.99) material temperatures close Tc. assumption that superconductivity occurs through Josephson effect yields scaling relation between strength superconducting condensate (ρs,c, measure number carriers), temperature, normal-state c-axis σdc just Tc; ρs,c ∝ This is observed all dopings, as well several other cuprate materials. However, agreement with coupling model does not necessarily imply transport, suggesting these materials may indeed be tending towards higher