The coupling of two dephased $s$-wave-pair order parameters is shown to induce two distinct low-symmetry superconducting states. One of these states is characterized by a breaking of the time-reversal symmetry, by a nonlinear magnetoelectric effect, and by a voltage threshold in the ac Josephson effect. The coupling mechanism is justified phenomenologically and microscopically.

• Received 17 June 1996

DOI:https://doi.org/10.1103/PhysRevLett.77.2284