Effect of out-of-plane disorder on Tc in high-Tc copper oxide superconductors

H. Eisaki, A. Sugimoto, S. Kashiwaya, K. Fujita*, S. Uchida*
AIST, 1-1-1 Umezono, Tsukuba, Ibaraki 305-8568, Japan
*Department of Physics, University of Tokyo, Tokyo 113-0033, Japan

Superconducting cuprates are usually chemically disordered, as in many cases the mobile carriers are introduced into the parent compound by chemical substitution which takes place away from CuO2 planes. In this study, the effect of the out-of-plane chemical disorder on their superconducting properties is examined in Bi2201 and LSCO. Partial substitution of A-site ions results in a monotonic decrease of Tc with increasing ionic radius mismatch, revealing that the out-of-plane disorder significantly decreases Tc without changing carrier density. The disorder-induced in-plane resistivity is significantly smaller than that induced by in-plane disorder such as Zn substitution for Cu, suggesting that the effect of out-of-plane disorder is distinct from the in-plane counterpart.