Crystal structures and superconductivities of (La,Sr)2CuO4/Sm2CuO4 and YBa2Cu3O7/(La,Sr)2CuO4 strained superlattices

Superconducting strained superlattices have been formed by epitaxial stacking along c-axes of two kinds of unit layers, such as (La, Sr)2CuO4/Sm2CuO4 and YBa2Cu3O7/(La, Sr)2CuO4. In the case of (La, Sr)2CuO4/Sm2CuO4 superlattice, the Tc becomes lower and ab-plane are expanded with decreasing the number of stacking layers. For YBa2Cu3O7/(La, Sr)2CuO4, on the other hand, the Tcend is 72K even in the range of 24A (2 unit layers) thickness of YBCO layer with the compression of the ab-plane. The correlation between the Tc and the in-plane strain along ab-axes observed here suggests that the pressure effect to change the Cu-O bond length along the CuO2 plane is important for the Tc value. (orig.)