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Proximity effects in high-TC superconducting hybrids - Javier Villegas - Mardi 21 juin 2016 à 11 h

INSP - 4 place Jussieu - 75252 PARIS Cedex 05 - Barre 22-32 - 2e étage, salle 201

Javier E. Villegas - Unité Mixte de Physique, CNRS, Thales, Univ. Paris-Sud, Université Paris Saclay


In artificial hybrids, competing interactions, interplay and proximity effects at the interface between the different constituents often yield to interesting physics, sometimes to novel effects and, occasionally, to new functionalities. In superconductor-based hybrids, one of the key interaction mechanisms is the proximity effect, via which superconducting correlations leak into a non-superconducting material, eventually allowing it to sustain supercurrents. This effect is very much affected not only by the pairing symmetry in the superconductor, but also by the electronic structure in the non-superconducting material. For example, the presence in the latter of a finite spin polarization (e.g. as in ferromagnets), Dirac fermions (i.e. as in graphene), or spin-orbit coupling (e.g. as in topological insulators) lead to a variety of “exotic” behaviors as compared to the normal-metals case. In this talk, I will review two examples on which we have been working these last years. The one is proximity effects at high-temperature superconductor / half-metal ferromagnet oxides, in which a long-range penetration of superconducting correlations is explained in terms of equal-spin triplet correlations. I will discuss the controversies, opportunities and challenges brought by this so-called spin-polarized superconductivity. The second example addresses proximity effects at high-temperature superconductors/graphene interfaces. I will discuss conductance experiments in which the Andreev reflection is modulated electrostatically due to electron interference effects and Klein-like tunneling at the superconducting/normal graphene interface.

Work supported by the French National Research Agency through “Investissements d’Avenir” program Labex NanoSaclay (ANR-10-LABX-0035) and grant ANR-15-CE24-0008-01, by the European Research Council through Consolidator grant Nº 64710 “SUSPINTRONICS”, and by COST project “NanoSC”.