Condensed Matter Seminar Series
Spin-Triplet Supercurrent in Ferromagnetic Josephson Junctions
Norman O. Birge
Michigan State University
Thursday September 22, 11:30 am, Room 298, Physics Building
When a superconductor (S) and a ferromagnet (F) are put into
contact with each other, interesting things happen, and the combined
S/F hybrid system exhibits altogether new properties. There is a
proximity effect where pair correlations from S penetrate into F, but
this proximity effect decays over a very short distance due to the
large energy splitting between the spin-up and spin-down
electrons. Theory predicts that, under certain conditions,
electron pair correlations will appear with spin-triplet rather than
spin-singlet symmetry . The two electrons in such a
spin-triplet pair have parallel spins and are not energy split in F;
hence they propagate long distances. Furthermore, these triplet
correlations satisfy the Pauli Exclusion Principle in a new and strange
way: they are odd in frequency or time. In this talk I will
discuss our recent observation of these pair correlations in
experiments with S/F/S Josephson junctions .
 F.S. Bergeret, A.F. Volkov, and K.B. Efetov, Rev. Mod. Phys. 77, 1321 (2005).
 T.S. Khaire, M.A. Khasawneh, W.P. Pratt, Jr., N.O. Birge, Phys. Rev. Lett. 104, 137002 (2010).
Host: Harold Baranger