Imaging spontaneous currents in superconducting arrays of π-junctions

Sergey M. Frolov, Micah J.A. Stoutimore, Trevis A. Crane, Dale J. Van Harlingen, Vladimir A. Oboznov, Valery V. Ryazanov, Adele Ruosi, Carmine Granata, Maurizio Russo

Research output: Contribution to journalArticlepeer-review


A charge current can flow between two superconductors separated by a thin barrier. This phenomenon is the Josephson effect, which enables a current to tunnel at zero voltage, typically with no phase shift between the superconductors in the lowest-energy state. Recently, Josephson junctions with ground-state phase shifts of , proposed by theory three decades ago, have been demonstrated. In superconducting loops, -junctions cause spontaneous circulation of persistent currents in zero magnetic field, in analogy to spin-1/2 systems. Here we use a scanning superconducting quantum interference device microscope to image the spontaneous zero-field currents in superconducting networks of temperature-controlled -junctions with weakly ferromagnetic barriers. We find an onset of spontaneous supercurrents at the 0- transition temperature of the junctions, T3 K. We image the currents in non-uniformly frustrated arrays consisting of cells with even and odd numbers of -junctions. Such arrays are attractive model systems for studying the exotic phases of the two-dimensional XY-model and achieving scalable adiabatic quantum computers.

Original languageEnglish (US)
Pages (from-to)32-36
Number of pages5
JournalNature Physics
Issue number1
StatePublished - Jan 2008

ASJC Scopus subject areas

  • General Physics and Astronomy


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