title: Strong interplay between stripe spin fluctuations, nematicity and superconductivity in FeSe.
abstract: In iron-based superconductors the interactions driving the nematic order (that breaks four-fold rotational symmetry in the iron plane) may also mediate the Cooper pairing. The experimental determination of these interactions, which are believed to depend on the orbital or the spin degrees of freedom, is challenging because nematic order occurs at, or slightly above, the ordering temperature of a stripe magnetic phase. Here, we study FeSe (ref. )-which exhibits a nematic (orthorhombic) phase transition at Ts = 90 K without antiferromagnetic ordering-by neutron scattering, finding substantial stripe spin fluctuations coupled with the nematicity that are enhanced abruptly on cooling through Ts. A sharp spin resonance develops in the superconducting state, whose energy (∼4 meV) is consistent with an electron-boson coupling mode revealed by scanning tunnelling spectroscopy. The magnetic spectral weight in FeSe is found to be comparable to that of the iron arsenides. Our results support recent theoretical proposals that both nematicity and superconductivity are driven by spin fluctuations.
authors.affiliation: State Key Laboratory of Surface Physics and Department of Physics, Fudan University, Shanghai 200433, China.
authors.forename: Qisi
authors.initials: Q
authors.lastname: Wang
authors.affiliation: State Key Laboratory of Surface Physics and Department of Physics, Fudan University, Shanghai 200433, China.
authors.forename: Yao
authors.initials: Y
authors.lastname: Shen
authors.affiliation: State Key Laboratory of Surface Physics and Department of Physics, Fudan University, Shanghai 200433, China.
authors.forename: Bingying
authors.initials: B
authors.lastname: Pan
authors.affiliation: State Key Laboratory of Surface Physics and Department of Physics, Fudan University, Shanghai 200433, China.
authors.forename: Yiqing
authors.initials: Y
authors.lastname: Hao
authors.affiliation: Beijing National Laboratory for Condensed Matter Physics, Institute of Physics, Chinese Academy of Science, Beijing 100190, China.
authors.forename: Mingwei
authors.initials: M
authors.lastname: Ma
authors.affiliation: Beijing National Laboratory for Condensed Matter Physics, Institute of Physics, Chinese Academy of Science, Beijing 100190, China.
authors.forename: Fang
authors.initials: F
authors.lastname: Zhou
authors.affiliation: Institut Laue-Langevin, 71 Avenue des Martyrs, 38042 Grenoble Cedex 9, France.
authors.forename: P
authors.initials: P
authors.lastname: Steffens
authors.affiliation: Juelich Centre for Neutron Science JCNS Forschungszentrum Juelich GmbH, Outstation at ILL, 38042 Grenoble, France.
authors.forename: K
authors.initials: K
authors.lastname: Schmalzl
authors.affiliation: European Synchrotron Radiation Facility, BP 220, 38043 Grenoble Cedex, France.
authors.forename: T R
authors.initials: TR
authors.lastname: Forrest
authors.affiliation: Center for High Pressure Science and Technology Advanced Research, Shanghai 201203, China.|Faculty of Science, Physics Department, Fayoum University, 63514 Fayoum, Egypt.
authors.forename: M
authors.initials: M
authors.lastname: Abdel-Hafiez
authors.affiliation: Center for High Pressure Science and Technology Advanced Research, Shanghai 201203, China.
authors.forename: Xiaojia
authors.identifier: http://orcid.org/0000-0002-3979-8369
authors.initials: X
authors.lastname: Chen
authors.affiliation: Institute of Experimental Mineralogy, Russian Academy of Sciences, Chernogolovka, Moscow District 142432, Russia.
authors.forename: D A
authors.initials: DA
authors.lastname: Chareev
authors.affiliation: Low Temperature Physics and Superconductivity Department, M.V. Lomonosov Moscow State University, Moscow 119991, Russia.|Theoretical Physics and Applied Mathematics Department, Ural Federal University, Ekaterinburg 620002, Russia.|National University of Science and Technology "MISiS", Moscow 119049, Russia.
authors.forename: A N
authors.initials: AN
authors.lastname: Vasiliev
authors.affiliation: Laboratoire Leon Brillouin, CEA-CNRS, CEA-Saclay, 91191 Gif sur Yvette, France.
authors.forename: P
authors.initials: P
authors.lastname: Bourges
authors.affiliation: Laboratoire Leon Brillouin, CEA-CNRS, CEA-Saclay, 91191 Gif sur Yvette, France.
authors.forename: Y
authors.initials: Y
authors.lastname: Sidis
authors.affiliation: Neutron Scattering Science Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831-6393, USA.
authors.forename: Huibo
authors.initials: H
authors.lastname: Cao
authors.affiliation: State Key Laboratory of Surface Physics and Department of Physics, Fudan University, Shanghai 200433, China.|Collaborative Innovation Center of Advanced Microstructures, Fudan University, Shanghai 200433, China.
authors.forename: Jun
authors.identifier: http://orcid.org/0000-0002-0421-8934
authors.initials: J
authors.lastname: Zhao