Nonequilibrium supercurrent in a mesoscopic four-terminal triplet Josephson junction

We investigate theoretically the nonequilibrium (NE) supercurrent flowing in a mesoscopic four-terminal triplet superconductor (TS)/normal metal (N)/triplet superconductor junction, of which the N region is a quantum dot (QD) connected via tunnel barriers to the two TS electrodes and two N electrodes, respectively. We find that both the charge and spin triplet supercurrents could be rapidly suppressed and even reversed by increasing the dc voltage applied across the two N electrodes because of the nonthermal electron energy distribution in the dot, similar to the singlet NE supercurrent in an s-wave superconductor system. The reversed NE triplet supercurrent almost vanishes when the bias equals the TS pair potential as long as the coupling between the N electrodes and the QD is not too weak. This arises from the zero-energy states of the TS Josephson junction making the current-carrying density of states vanish nearly outside the energy gap. It is also shown that in this nonmagnetic system the currents flowing in the N electrodes are spin-polarized and can be modulated by the TS phases owing to the quantum interference effect. © 2012 Copyright EPLA.