AQP Seminar: Ballistic SNS sandwich as a Josephson junction
The work develops the theory of the ballistic SNS sandwich, in which the Josephson effect exists without the proximity effect. The theory takes into account restrictions imposed by the charge conservation law and the incommensurability of the superconducting gap with the Andreev level energy spacing. This resulted in revisions of some conclusions of previous works. In the one-dimensional case, the Josephson phase of the ground state of the ballistic SNS sandwich is not necessarily zero but may have any value from 0 to π. If this value is π this is a π junction, which was well known before. The suppression of the supercurrent at temperatures on the order or higher than the Andreev level energy spacing, which was predicted in previous investigations, does not take place in the one-dimensional case. The analysis demonstrates that the ballistic SNS sandwich has unusual properties, which distinguish it from a usual Josephson junction, in particular, the absence of the Josephson plasma mode localized at the normal layer and the Meisner effect with the same London penetration depth in the normal and the superconducting layers.
 E. B. Sonin, Ballistic SNS sandwich as a Josephson junction, Phys.Rev. B 104, 094517 (2021).