Superconducting symmetries of nano-structured anisotropic superconductors

Using the Bogoliubov-de Gennes equation, nano-structured anisotropic superconductors are investigated. The symmetry of order parameter strongly depends on its shape. For π/4 rotated square superconductors, s + i d superconductivity becomes stable. And because of broken time-reversal symmetry of this state, there appear spontaneous currents around the boundary. This result shows shape of the superconductors controls their superconducting symmetry.