Spin transport and giant thermomagnetics effects in ferromagnetic/superconductor structures

Par Mihail Silaev, KTH Royal institute of technology, Stockholm, Sweden

Mercredi 23 Mars, 14h, Salle des séminaires, 3ème étage, Batiment A4

Abstract :

Recent studies of non-equilibrium spin states in superconductors revealed a rich physics originating from the interplay between magnetism and superconductivity. Several experiments [1,2] observed a giant spin accumulation available in superconducting wires generated by the current injected from normal electrodes. The striking phenomenon of an extra-large spin relaxation length and time in superconductors with strong Zeeman splitting has been reported. In this talk I will suggest a theoretical explanation of these experiments. It will be shown that a non-equilibrium spin polarization can be generated from heat injection due to the peculiar thermomagnetic effect in superconducting wires [3]. Various possibilities of generating long-living non-equilibrium spin states and manipulating spin-polarized currents in superconductors will be discussed. I will demonstrate that superconductivity can either strongly enhance or suppress the coherent spin rotation [4], depending on the type of spin relaxation mechanism being dominated either by spin-orbit coupling or spin-flip scattering at impurities.

References :

[1] C.H.L. Quay, D. Chevallier, C. Bena, M. Aprili, Nature Phys. 9, 84 (2013).
[2] F. Hübler, M.J. Wolf, D. Beckmann, H. v. Löhneysen, Phys. Rev. Lett. 109, 207001 (2012).
[3] M. Silaev, P. Virtanen, F. S. Bergeret, and T. T. Heikkilä, Long-Range Spin Accumulation from Heat Injection in Mesoscopic Superconductors with Zeeman Splitting, Phys. Rev. Lett. 114, 167002 (2015).
[4] M. Silaev, P. Virtanen, T. T. Heikkilä, and F. S. Bergeret, Spin Hanle effect in mesoscopic superconductors, Phys. Rev. B 91, 024506 (2015).