Novel superconducting quantum structures based on build-in pi-phase shifts

Many experiments have provided strong evidence for a predominant d-wave pairing symmetry in the high temperature superconductors. The associated sign changes in the phase of the wave function for orthogonal directions in the CuO2 planes, provide intriguing opportunities to realize novel Josephson quantum-structures, characterized by build-in pi-phase shifts. Such elements are of interest for basic studies and have also been proposed as new components in superconducting (quantum)-electronics. We have realized various novel quantum structures with such build-in pi-phase shifts, based on Josephson contacts between high-Tc and low-Tc superconductors [1]. These include arrays of zigzag- and corner-junctions, which spontaneously produce ordered arrays of half-integer magnetic flux quanta in their energetic ground states. Additional elements include pi-SQUIDs and switchable {1/2}p-SQUIDs. The fabrication and characteristics of these structures will be presented and possible directions for future research will be outlined. [1]: H. Hilgenkamp et al., Nature 422, 50 (2003).