A new class of superconductivity-enhanced, quasi-particle interference effects (SEQUINS) is suggested, based on interference from the order parameter phase gradient of a single superconductor (S) in contact with a normal metallic lead (N) of finite width M. By solving the Bogoliubov-de Gennes equation in two dimensions, it is predicted that the electrical conductance will oscillate as the phase gradient w at 90" to the interface is increased, with period V = 2x/M. This effect is enhanced by the presence of a Schottky barrier at the interface and is also present in N-S-N structures. The size of the effect scales with the number of open channels and can be much greater than e 2 / h .

We examine the effect of d-wave symmetry on zero bias anomalies in normal-superconducting tunnel junctions and phase-periodic conductances in Andreev interferometers. In the presence of d-wave pairing, zero-bias anomalies are suppressed compared with the s-wave case. For Andreev interferometers with aligned islands, the phase-periodic conductance is insensistive to the nature of the pairing, whereas for non-aligned islands, the nature of zero-phase extremum is reversed.

We compute the current-voltage (I-V) characteristic of a mesoscopic Josephson junction, formed from two weakly linked, superconducting dots. A key feature of such structures is the presence of quasi-particle resonances in the current-phase relation. We show that these lead to measurable changes in the I-V characteristic compared with conventional macroscopic junctions. For an overdamped junction, the I-V characteristic is predicted to shift to higher values of the current, but the critical current is unchanged. For an underdamped junction exhibiting hysteresis, this shift is accompanied by an increase in the critical current associated with the lower branch of the I-V curve.

We examine the effect of d-wave symmetry on zero bias anomalies in normal-superconducting tunnel junctions and phase-periodic conductances in Andreev interferometers. In the presence of d-wave pairing, zero-bias anomalies are suppressed compared with the s-wave case. For Andreev interferometers with aligned islands, the phase-periodic conductance is insensistive to the nature of the pairing, whereas for non-aligned islands, the nature of zero-phase extremum is reversed.