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TT: Fachverband Tiefe Temperaturen
TT 14: Superconductivity: Tunnelling, Josephson Junctions, SQUIDs 1
TT 14.3: Talk
Monday, March 20, 2017, 15:30–15:45, HSZ 201
Scanning tunneling spectroscopy to probe odd-triplet contributions to the long-ranged proximity effect in Al-EuS — •Simon Diesch1, Christoph Sürgers2, Detlef Beckmann2, Peter Machon1, Wolfgang Belzig1, and Elke Scheer1 — 1Universität Konstanz, 78457 Konstanz, Germany — 2Karlsruhe Institute of Technology, 76344 Karlsruhe, Germany
In conventional superconductors, electrons are bound in singlet Cooper pairs, i.e. with opposite spin. More recently, experiments on superconductor-ferromagnet systems have shown supercurrents tunneling through ferromagnetic layers, indicating Cooper pairs of equal spin, thus corresponding to a long-range triplet proximity effect [1]. Most experimental evidence for triplet superconductivity comes from observations of the thickness dependence of the Josephson current through a ferromagnetic barrier, and there is now an increasing amount of direct spectroscopic evidence [2] to test the existing theoretical models. In this talk we present scanning tunneling spectra of thin films of the ferromagnetic insulator europium sulfide on superconducting aluminum measured at 280 mK and in varying magnetic fields. We observe significant broadening of the superconducting energy gap and a variety of sub-gap structures induced by the presence of the ferromagnet. We interpret our findings based on the diffusive theory and a more advanced circuit theory model [3].
[1] F. S. Bergeret, Phys. Rev. Lett. 86, 4096 (2001)
[2] A. Di Bernardo, Nat. Comm. 6:8053 (2015)
[3] P. Machon, Phys. Rev. Lett. 110, 047002 (2013)