It was found [1] that Nb-Cu_1-xNi_x-Nb (SFS) sandwiches can reveal the crossover to the Josephson pi-state with different signs of the superconducting order parameter at the two banks of the junction. This effect owes its origin to spatial oscillations of the superconducting order parameter due to the exchange field. The SFS junctions showed the reentrant temperature dependence of the critical current with vanishing amplitude at Tcr. We have reported in [2] that the crossover to the pi-state also manifested itself in the half-period shift of the magnetic field dependence of the critical current in the triangular SFS arrays. The shift is associated with the appearance of spontaneous supercurrents in the array even in case of zero field, with the ground state degenerated with respect to the two possible current flow directions. 'Self-frustrated' superconducting networks with pi-junctions may be used for the realization of the superconducting quantum bit [3] and new superconducting 'complementary' electronics [4] based on the analogy to complementary metal-oxide-semiconductor (CMOS) logic family.

1. V.V.Ryazanov et al. Phys. Rev. Lett. 86, 2427 (2001).
2. V.V.Ryazanov et al. Phys. Rev. B 65, 020501(R) (2002).
3. G. Blatter et al. Phys. Rev. B 63, 174511 (2002).
4. E.Terzioglu, M.R.Beasley. IEEE Trans. Appl. Superc. 8, 48 (1998).