Conductance Fluctuation of the Normal Metal in an SNS Structure

The conductance of a clean normal metal spanning between two superconductors (SNS structure) has been investigated. It is found that the conductance fluctuates periodically with the phase difference of two superconductors. When the pairing symmetry in one side of the superconductors is d_x²-y², the fluctuation period tends to be π instead of 2π, and the phase dependence of its conductance depends strongly on the orientation of the junction in contradistinction to the s-wave case. It can be used as a new method to determine the pairing symmetry of the high-Tc superconductors.