Resistivities of ceramic and single-crystalline superconducting oxides to 1100K: What do they tell us?

Abstract Resistivities ϱ(T) of ceramic samples of La 1.825 Sr 0.175 CuO 4 (LSCO) and both ceramic and single-crystalline (a-b plane, containing micro-twins) samples of YBa 2 Cu 3 O 7 (YBCO) were measured from T c to 1100K. The observed absence of saturation in the linear parts of ϱ(T) implies weak electron-phonon coupling in both superconductors, thus excluding the possibility of phonon-mediated superconductivity. Oxygen desorption causes faster than linear dependence at T > 800 K in YBCO crystals (compared to T > 600 K for ceramics), demonstrating that inelastic scattering is linear in T up to at least 800 K.