Giant nonreciprocity of current-voltage characteristics of noncentrosymmetric superconductor-normal metal-superconductor junctions

We develop a theory of nonreciprocal current-voltage (I-U) characteristics in noncentrosymmetric superconductor-normal metal-superconductor junctions. We show that at small voltages the nonreciprocal features of the I-U characteristics can be expressed entirely in terms of the dependence of the nonreciprocal part of the quasiparticle density of states in the normal metal part of the junction on the order parameter phase difference chi across the junction. The amplitude of the nonreciprocity in this regime is proportional to the inelastic quasiparticle relaxation time tau in, and can be much larger than that in normal materials, where it is proportional to the elastic relaxation time tau el. At low bias the I-U characteristics possess additional symmetry not present in normal conductors; they remain invariant under simultaneous reversal of current, voltage, and the magnetic field.