title: Superconducting gap structure of FeSe.
abstract: The microscopic mechanism governing the zero-resistance flow of current in some iron-based, high-temperature superconducting materials is not well understood up to now. A central issue concerning the investigation of these materials is their superconducting gap symmetry and structure. Here we present a combined study of low-temperature specific heat and scanning tunnelling microscopy measurements on single crystalline FeSe. The results reveal the existence of at least two superconducting gaps which can be represented by a phenomenological two-band model. The analysis of the specific heat suggests significant anisotropy in the gap magnitude with deep gap minima. The tunneling spectra display an overall "U"-shaped gap close to the Fermi level away as well as on top of twin boundaries. These results are compatible with the anisotropic nodeless models describing superconductivity in FeSe.
authors.affiliation: Max Planck Institute for Chemical Physics of Solids, Nöthnitzer Straße 40, 01187 Dresden, Germany.
authors.forename: Lin
authors.initials: L
authors.lastname: Jiao
authors.affiliation: Max Planck Institute for Chemical Physics of Solids, Nöthnitzer Straße 40, 01187 Dresden, Germany.
authors.forename: Chien-Lung
authors.initials: CL
authors.lastname: Huang
authors.affiliation: Max Planck Institute for Chemical Physics of Solids, Nöthnitzer Straße 40, 01187 Dresden, Germany.
authors.forename: Sahana
authors.initials: S
authors.lastname: Rößler
authors.affiliation: Max Planck Institute for Chemical Physics of Solids, Nöthnitzer Straße 40, 01187 Dresden, Germany.
authors.forename: Cevriye
authors.initials: C
authors.lastname: Koz
authors.affiliation: IFW Dresden, Postfach 270016, 01171 Dresden, Germany.
authors.forename: Ulrich K
authors.initials: UK
authors.lastname: Rößler
authors.affiliation: Max Planck Institute for Chemical Physics of Solids, Nöthnitzer Straße 40, 01187 Dresden, Germany.
authors.forename: Ulrich
authors.initials: U
authors.lastname: Schwarz
authors.affiliation: Max Planck Institute for Chemical Physics of Solids, Nöthnitzer Straße 40, 01187 Dresden, Germany.
authors.forename: Steffen
authors.initials: S
authors.lastname: Wirth