Phase-dependent multiple Andreev reflections in SNS interferometers

A theory of coherent multiple Andreev reflections (MAR) is developed for superconductor-normal-metal-superconductor interferometers. We consider a Y-shaped normal-electron-beam splitter connecting two superconducting reservoirs, where the two connection points to the same superconductor can have different phases. The current is calculated in the quantum transport regime as a function of applied voltage and phase difference, I(V,phi). MAR in interferometers incorporate two features: interference in the arms of the splitter, and interplay with Andreev resonances. The latter feature yields enhancement of the subgap current and current peaks with phase-dependent positions and magnitudes. The interference effect leads to suppression of the subgap current and complete disappearance of the current peaks at phi=pi. The excess current at large voltage decreases and changes sign with increasing phase difference.