Observation of Supercurrent Enhancement in SNS Junctions by Nonequilibrium Injection into Supercurrent Carrying Bound Andreev States

We report for the first time enhancement of the supercurrent by means of injection in a mesoscopic three terminal planar SN-SNS device made of Al on GaAs. When a current is injected from one of the superconducting Al electrodes at an injection bias $V=\Delta \left(T\right)/e$, the dc Josephson current between the other two superconducting electrodes has a maximum, giving evidence for an enhancement due to a nonequilibrium injection into bound Andreev states of the underlying semiconductor. The effect persists to temperatures where the equilibrium supercurrent has vanished.