title: Pairing mechanism in the ferromagnetic superconductor UCoGe.
abstract: Superconductivity is a unique manifestation of quantum mechanics on a macroscopic scale, and one of the rare examples of many-body phenomena that can be explained by predictive, quantitative theories. The superconducting ground state is described as a condensate of Cooper pairs, and a major challenge has been to understand which mechanisms could lead to a bound state between two electrons, despite the large Coulomb repulsion. An even bigger challenge is to identify experimentally this pairing mechanism, notably in unconventional superconductors dominated by strong electronic correlations, like in high-Tc cuprates, iron pnictides or heavy-fermion compounds. Here we show that in the ferromagnetic superconductor UCoGe, the field dependence of the pairing strength influences dramatically its macroscopic properties like the superconducting upper critical field, in a way that can be quantitatively understood. This provides a simple demonstration of the dominant role of ferromagnetic spin fluctuations in the pairing mechanism.
authors.affiliation: Université Grenoble Alpes, CEA, INAC-PHELIQS, F-38000 Grenoble, France.
authors.forename: Beilun
authors.initials: B
authors.lastname: Wu
authors.affiliation: Université Grenoble Alpes, CEA, INAC-PHELIQS, F-38000 Grenoble, France.
authors.forename: Gaël
authors.initials: G
authors.lastname: Bastien
authors.affiliation: Université Grenoble Alpes, CEA, INAC-PHELIQS, F-38000 Grenoble, France.|Institute of Solid State Physics, Vienna University of Technology, Wiedner Hauptstrasse 8-10, Vienna 1040, Austria.
authors.forename: Mathieu
authors.initials: M
authors.lastname: Taupin
authors.affiliation: Université Grenoble Alpes, CNRS, F-38000 Grenoble, France.
authors.forename: Carley
authors.initials: C
authors.lastname: Paulsen
authors.affiliation: Université Grenoble Alpes, CEA, INAC-PHELIQS, F-38000 Grenoble, France.|Swiss Light Source, Paul Scherrer Institut, CH-5232 Villigen PSI, Switzerland.
authors.forename: Ludovic
authors.initials: L
authors.lastname: Howald
authors.affiliation: Université Grenoble Alpes, CEA, INAC-PHELIQS, F-38000 Grenoble, France.|Institute for Materials Research, Tohoku University, Oarai, Ibaraki 311-1313, Japan.
authors.forename: Dai
authors.initials: D
authors.lastname: Aoki
authors.affiliation: Université Grenoble Alpes, CEA, INAC-PHELIQS, F-38000 Grenoble, France.
authors.forename: Jean-Pascal
authors.initials: JP
authors.lastname: Brison