On the Ginzburg–Landau analysis of a mixed s–dx2−y2-wave superconducting mesoscopic square

The self-consistent solution of the coupled Ginzburg–Landau equations for the s- and d-wave order parameters is obtained in a mesoscopic square of a mixed s–dx2−y2-wave superconductor which serves as a model of high-Tc cuprates. The spatial distributions of the order parameters in the square are shown to be fourfold symmetric. The shape of the calculated distributions reflects the internal symmetry of the d-wave electron pairing as well as the geometry of the mesoscopic square. The analysis of the phase and the amplitude of the d-wave order parameter for low applied magnetic fields reveals a specific behaviour of the current which appears in an external lead connected to the midpoints of the adjacent sides of the square. For a YBa2Cu3O7 square with a side length of 1 μm, the current reaches its maximal value ∼2.2 μA at zero applied magnetic field.