The observed behavior implies that Andreev bound states are forming in the system and are responsible for coherent transport both at zero and finite voltage.
A novel band structure was found in multiple-barrier SINININIS devices. The structure persists up to energies higher than the total gap-sum energy for the device. The structure is sensitive to a weak applied magnetic field and therefore is due to coherent transport.
For asymmetric Sn-I-Pb voltage-biased junctions, it is found that a peculiar shape of the CVC in the region (DPb-DSn)/e<V<(DPb+DSn)/e with negative differential resistance is due to relaxation oscillations taking place between the two quasparticle branches in the CVC.
On the basis of the research carried out, new devices (in particular, three-terminal ones) have been proposed for cryoelectronics applications.
Key words: superconductivity, tunneling, Josephson effect, Andreev reflection, nonequilibrium superconductivity, proximity effect, relaxation oscillations