Spectroscopic evidence of odd frequency superconducting order

Spin filter superconducting S/I/N tunnel junctions (NbN/GdN/TiN) show a robust and pronounced zero bias conductance peak at low temperatures, the magnitude of which is several times the normal state conductance of the junction. Such a conductance anomaly is representative of unconventional superconductivity and is interpreted as a direct signature of an odd frequency superconducting order.Comment: 5 pages, 3 figures + supplementary informatio

Remotely induced magnetism in a normal metal using a superconducting spin-valve

Superconducting spintronics has emerged in the past decade as a promising new field that seeks to open a new dimension for nanoelectronics by utilizing the internal spin structure of the superconducting Cooper pair as a new degree of freedom1, 2. Its basic building blocks are spin-triplet Cooper pairs with equally aligned spins, which are promoted by proximity of a conventional superconductor to a ferromagnetic material with inhomogeneous macroscopic magnetization3. Using low-energy muon spin-rotation experiments we find an unanticipated effect, in contradiction with the existing theoretical models of superconductivity and ferromagnetism: the appearance of a magnetization in a thin layer of a non-magnetic metal (gold), separated from a ferromagnetic double layer by a 50-nm-thick superconducting layer of Nb. The effect can be controlled either by temperature or by using a magnetic field to control the state of the remote ferromagnetic elements, and may act as a basic building block for a new generation of quantum interference devices based on the spin of a Cooper pair

Pt and CoB trilayer Josephson π junctions with perpendicular magnetic anisotropy

We report on the electrical transport properties of Nb based Josephson junctions with Pt/Co68B32/Pt ferromagnetic barriers. The barriers exhibit perpendicular magnetic anisotropy, which has the main advantage for potential applications over magnetisation in-plane systems of not affecting the Fraunhofer response of the junction. In addition, we report that there is no magnetic dead layer at the Pt/Co68B32 interfaces, allowing us to study barriers with ultra-thin Co68B32. In the junctions, we observe that the magnitude of the critical current oscillates with increasing thickness of the Co68B32 strong ferromagnetic alloy layer. The oscillations are attributed to the ground state phase difference across the junctions being modified from zero to π. The multiple oscillations in the thickness range 0.2 ⩽ dCoB ⩽ 1.4 nm suggests that we have access to the first zero-π and π-zero phase transitions. Our results fuel the development of low-temperature memory devices based on ferromagnetic Josephson junctions

Stimulation of a Singlet Superconductivity in SFS Weak Links by Spin-Exchange Scattering of Cooper Pairs

Josephson junctions with a ferromagnetic metal weak link reveal a very strong decrease of the critical current compared to a normal metal weak link. We demonstrate that in the ballistic regime the presence of a small region with a non-collinear magnetization near the center of a ferromagnetic weak link restores the critical current inherent to the normal metal. The above effect can be stimulated by additional electrical bias of the magnetic gate which induces a local electron depletion of ferromagnetic barrier. The underlying physics of the effect is the interference phenomena due to the magnetic scattering of the Cooper pair, which reverses its total momentum in the ferromagnet and thus compensates the phase gain before and after the spin-reversed scattering. In contrast with the widely discussed triplet long ranged proximity effect we elucidate a new singlet long ranged proximity effect. This phenomenon opens a way to easily control the properties of SFS junctions and inversely to manipulate the magnetic moment via the Josephson current.Etats de Majorana et d'Andreev dans des circuits hybrides combinant des matériaux magnétiques et supraconducteursNew Century of Superconductivity: Ideas, Materials, Technologie