Effect of HgI2 intercalation on Bi2Sr2CaCu2Oy: Interlayer coupling effect

By intercalating large HgI2 molecules between the Bi2O2 layers in Bi2Sr2CaCu2Oy, the distance between the CuO2 blocks was significantly extended up to 7.2 Angstrom. The superconducting properties of this system were measured in various magnetic fields applied perpendicular to the CuO2 planes. This system showed large positional fluctuation of the vortex even far below the transition temperature due to the reduction of dimensionality. The change of the thermodynamic parameters is well explained by the model of Josephson-coupled superconductivity. However, the interlayer coupling strength did not change the transition temperature drastically, which does not support the suggestion of Wheatley, Hsu, and Anderson of coherent hopping of the valence bond pair between the CuO2 layers.