Berlin 2015 – scientific programme
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TT: Fachverband Tiefe Temperaturen
TT 84: Focus Session: Nanoscopic Superconducting Heterostructures
TT 84.6: Talk
Thursday, March 19, 2015, 12:15–12:30, H 0104
Probing odd-triplet contributions to the long-ranged proximity effect by scanning tunneling spectroscopy — •Simon Diesch1, Christoph Sürgers2, Detlef Beckmann2, Peter Machon1, Wolfgang Belzig1, and Elke Scheer1 — 1Universität Konstanz, Konstanz, Germany — 2Karlsruhe Institute of Technology, 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 Cooper pairs tunneling through ferromagnetic layers, indicating Cooper pairs of equal spin, thus corresponding to a long-range triplet proximity effect. Most experimental evidence for triplet superconductivity comes from observations of the thickness dependence of the Josephson current through a ferromagnetic barrier, but there is an increasing interest in obtaining direct spectroscopic evidence.
This project aims at analyzing the electronic density of states of a thin diffusive normal metal layer (Ag) coupled to a superconductor (Al) across a ferromagnetic insulator (EuS) using a scanning tunneling microscope in spectroscopy mode at 280 mK. For this purpose, we fabricated EuS films of different thicknesses and acquired spectroscopic data at different magnetic fields. We observe significant broadening of the superconductive energy gap and a variety of sub-gap structures including zero-bias conductance peaks induced by the presence of the ferromagnet.