Department of Physics, Institute of Superconductivity and Institute of Nano Technology, Bar-Ilan University, Israel
I will report on our new magnetoresistance measurements in a granular Nb nano-ring revealing current-induced crossover between two distinct quantum coherence effects. At low bias currents, Cooper-pairs coherence is manifested by Little-Parks oscillations with flux periodicity of h/2e. At high bias currents, magnetoresistance oscillations with flux period of h/e are observed and interpreted as Aharonov-Bohm oscillations, reflecting phase coherence of individual quasi-particles. The model explaining these data views the ring as a chain of superconducting grains weakly coupled by tunnel junctions. Low bias currents allow coherent tunneling of Cooper pairs between the grains. Increasing the current above the critical current of all the junctions creates a quasi-particles conduction channel along the ring, allowing for quantum interference of quasi-particles.
At the end of my talk I will review briefly the applied-oriented research projects carried out at my lab, focusing on our progress in the design of Fault Current Limiters (FCLs). I will describe our saturated-core FCL that have already been installed in UK utilities and a novel design of a Limiter based on permanent magnets.
Prof. Yosef Yeshurun, Director of the Superconductivity Institute and Head of the Center for Magnetic Measurements, completed his university education in Israel, continued with advanced post-doctoral research at the University of Illinois, Urbana-Champaign. He also spent sabbatical years at IBM research laboratories at Yorktown Heights, Imperial College, London, New York University and City College of New York. Prof. Yeshurun has served in many capacities at Bar-Ilan University, including Head of the Department of Physics, Dean of Students, and Rector of the University. In addition, Prof. Yeshurun was an active member of Israeli national bodies such as the Council for Higher Education, and the National Research and Development Council.