Chemical Pressure Effect on Superconductivity of BiS 2 -Based Ce 1- x Nd x O 1- y F y BiS 2 and Nd 1- z Sm z O 1- y F y BiS 2

We have studied crystal structure and physical properties of REO1−yFyBiS2 (Ce1−xNdxO1−yFyBiS2 and Nd1−zSmzO1−yFyBiS2) with three different F concentration (y = 0.7, 0.5, and 0.3) to investigate relationship between the emergence of superconductivity and crystal structure in the REO1−yFyBiS2 series. REO1−yFyBiS2 is suitable for discussing chemical pressure effect on physical properties because the RE site at the blocking layer can be fully or partially substituted by various RE3+ ions, which could systematically tune the lattice volume. With increasing chemical pressure (with decreasing lattice volume), lattice constant of a-axis systematically decreases while lattice constant of c-axis does not show a remarkable change, indicating that the RE site substitution basically affect the lattice constant of a-axis. On the other hand, lattice constant of c-axis can be tuned by F concentration. On the basis of magnetic susceptibility measurements, we have obtained three kinds of superconductivity phase diagram wit...