title: Magnetic moments induce strong phonon renormalization in FeSi.
abstract: The interactions of electronic, spin and lattice degrees of freedom in solids result in complex phase diagrams, new emergent phenomena and technical applications. While electron-phonon coupling is well understood, and interactions between spin and electronic excitations are intensely investigated, only little is known about the dynamic interactions between spin and lattice excitations. Noncentrosymmetric FeSi is known to undergo with increasing temperature a crossover from insulating to metallic behaviour with concomitant magnetic fluctuations, and exhibits strongly temperature-dependent phonon energies. Here we show by detailed inelastic neutron-scattering measurements and ab initio calculations that the phonon renormalization in FeSi is linked to its unconventional magnetic properties. Electronic states mediating conventional electron-phonon coupling are only activated in the presence of strong magnetic fluctuations. Furthermore, phonons entailing strongly varying Fe-Fe distances are damped via dynamic coupling to the temperature-induced magnetic moments, highlighting FeSi as a material with direct spin-phonon coupling and multiple interaction paths.
authors.affiliation: Institute for Solid State Physics, Karlsruhe Institute of Technology, 76021 Karlsruhe, Germany.
authors.forename: S
authors.initials: S
authors.lastname: Krannich
authors.affiliation: Laboratoire Léon Brillouin (CEA-CNRS), CEA Saclay, F-91911 Gif-sur-Yvette, France.
authors.forename: Y
authors.initials: Y
authors.lastname: Sidis
authors.affiliation: Institute for Solid State Physics, Karlsruhe Institute of Technology, 76021 Karlsruhe, Germany.|Laboratoire Léon Brillouin (CEA-CNRS), CEA Saclay, F-91911 Gif-sur-Yvette, France.
authors.forename: D
authors.initials: D
authors.lastname: Lamago
authors.affiliation: Institute for Solid State Physics, Karlsruhe Institute of Technology, 76021 Karlsruhe, Germany.
authors.forename: R
authors.initials: R
authors.lastname: Heid
authors.affiliation: Laboratoire Léon Brillouin (CEA-CNRS), CEA Saclay, F-91911 Gif-sur-Yvette, France.
authors.forename: J-M
authors.initials: JM
authors.lastname: Mignot
authors.affiliation: Institute for Solid State Physics, Karlsruhe Institute of Technology, 76021 Karlsruhe, Germany.|Physics Institute, Karlsruhe Institute of Technology, 76049 Karlsruhe, Germany.
authors.forename: H v
authors.initials: Hv
authors.lastname: Löhneysen
authors.affiliation: Institute Laue-Langevin, BP 156, 38042 Grenoble, France.
authors.forename: A
authors.initials: A
authors.lastname: Ivanov
authors.affiliation: Institute Laue-Langevin, BP 156, 38042 Grenoble, France.
authors.forename: P
authors.initials: P
authors.lastname: Steffens
authors.affiliation: Max Planck Institute for Solid State Research, D-70569 Stuttgart, Germany.|Max Planck Society, Outstation at the FRM II, D-85748 Garching, Germany.
authors.forename: T
authors.identifier: http://orcid.org/0000-0001-5600-4914
authors.initials: T
authors.lastname: Keller
authors.affiliation: Institute for Solid State Physics, Karlsruhe Institute of Technology, 76021 Karlsruhe, Germany.
authors.forename: L
authors.initials: L
authors.lastname: Wang
authors.affiliation: Max Planck Institute for Intelligent Systems, 70569 Stuttgart, Germany.
authors.forename: E
authors.initials: E
authors.lastname: Goering
authors.affiliation: Institute for Solid State Physics, Karlsruhe Institute of Technology, 76021 Karlsruhe, Germany.
authors.forename: F
authors.initials: F
authors.lastname: Weber