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Discovery of orbital-selective Cooper pairing in FeSe

TitleDiscovery of orbital-selective Cooper pairing in FeSe
Publication TypeJournal Article
Year of Publication2017
AuthorsSprau, PO, Kostin, A, Kreisel, A, Bohmer, AE, Taufour, V, Canfield, PC, Mukherjee, S, Hirschfeld, PJ, Andersen, BM, Davis, JCS
Date Published07
Type of ArticleArticle
ISBN Number0036-8075
Accession NumberWOS:000416909500005
Keywordsfrustration, iron chalcogenides, nematicity, quasi-particle interference, superconductivity, symmetry, Technology - Other Topics

The superconductor iron selenide (FeSe) is of intense interest owing to its unusual nonmagnetic nematic state and potential for high-temperature superconductivity. But its Cooper pairing mechanism has not been determined. We used Bogoliubov quasiparticle interference imaging to determine the Fermi surface geometry of the electronic bands surrounding the Gamma = ( 0, 0) and X = (pi/a(Fe), 0) points of FeSe and to measure the corresponding superconducting energy gaps. We show that both gaps are extremely anisotropic but nodeless and that they exhibit gap maxima oriented orthogonally in momentum space. Moreover, by implementing a novel technique, we demonstrate that these gaps have opposite sign with respect to each other. This complex gap configuration reveals the existence of orbital-selective Cooper pairing that, in FeSe, is based preferentially on electrons from the d(yz) orbitals of the iron atoms.

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Complex States