Novel anisotropic superconductivity in nano-structured superconductors

Using the Bogoliubov-de Gennes equation of a tight-binding electron model with attractive on-site and nearest-neighbor sites interactions, we investigate the superconducting structure of nano-structured anisotropic superconductors. Numerical results show that nano-scaled π/4-rotated square d-wave superconductors show various type of superconductivities depending on the size. Especially, s+id superconductivity, appears when size of superconductors is 10 times of coherence length.