2007/08/01 by Sergey M. Frolov, Sergey Frolov, M. J. A. Stoutimore +14 · 48 citations
Physics and Astronomy · #Adiabatic process #Advanced Condensed Matter Physics #Condensed matter physics #Josephson effect #Physics #Physics of Superconductivity and Magnetism #Pi Josephson junction #Quantum and electron transport phenomena #Quantum mechanics #Quantum tunnelling #Squid #Superconductivity #cond-mat.mes-hall #cond-mat.supr-con
paper · pdf · doi:10.1038/nphys780
published in Nature Physics 4(1), 32-36 (Nature Portfolio) · Pre-referee version. Accepted to Nature Physics
arxiv created 2007/08/01 · openalex publication_date 2007/11/25 · arxiv updated 2015/05/12 · openalex created_date 2016/06/24 · openalex updated_date 2026/08/06
Superconductors separated by a thin tunneling barrier exhibit the Josephson effect that allows charge transport 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 pi proposed by theory three decades ago have been demonstrated. In superconducting loops, pi-junctions cause spontaneous circulation of persistent currents in zero magnetic field, analogous to spin-1/2 systems. Here we image the spontaneous zero-field currents in superconducting networks of temperature-controlled pi-junctions with weakly ferromagnetic barriers using a scanning SQUID microscope. We find an onset of spontaneous supercurrents at the 0-pi transition temperature of the junctions Tpi = 3 K. We image the currents in non-uniformly frustrated arrays consisting of cells with even and odd numbers of pi-junctions. Such arrays are attractive model systems for studying the exotic phases of the 2D XY-model and achieving scalable adiabatic quantum computers.