CPM Seminar

Spin-triplet superconductivity in Co-based Josephson junctions

Norman O. Birge

Department of Physics
Michigan State University

Superconducting/Ferromagnetic (S/F) hybrid systems exhibit a number of interesting properties due to the interplay between the competing symmetries of their order parameters. With conventional spin-singlet superconductors, the proximity effect in S/F systems decays over an extremely short length scale in the ferromagnet due to the large exchange splitting between the spin-up and spin-down electron bands. In S/F/S Josephson junctions, the critical current oscillates and decays rapidly as a function of the ferromagnetic layer thickness. If there were spin-triplet superconducting correlations present, however, then both the proximity and Josephson effects would persist over much longer distances. Such correlations have been predicted to occur in S/F systems with certain forms of magnetic heterogeneity near the S/F interface. Moreover, these correlations exhibit a strange symmetry never before observed: they are odd in frequency or time. In this talk I will discuss our efforts to produce and measure these elusive spin-triplet correlations in S/F/S Josephson junctions, culminating in our very recent success[1].

[1] T.S. Khaire, M.A. Khasawneh, W.P. Pratt, Jr., N.O. Birge, arXiv:0912.0205