title: Hour-glass magnetic excitations induced by nanoscopic phase separation in cobalt oxides.
abstract: The magnetic excitations in the cuprate superconductors might be essential for an understanding of high-temperature superconductivity. In these cuprate superconductors the magnetic excitation spectrum resembles an hour-glass and certain resonant magnetic excitations within are believed to be connected to the pairing mechanism, which is corroborated by the observation of a universal linear scaling of superconducting gap and magnetic resonance energy. So far, charge stripes are widely believed to be involved in the physics of hour-glass spectra. Here we study an isostructural cobaltate that also exhibits an hour-glass magnetic spectrum. Instead of the expected charge stripe order we observe nano phase separation and unravel a microscopically split origin of hour-glass spectra on the nano scale pointing to a connection between the magnetic resonance peak and the spin gap originating in islands of the antiferromagnetic parent insulator. Our findings open new ways to theories of magnetic excitations and superconductivity in cuprate superconductors.
authors.affiliation: Max-Planck-Institute for Chemical Physics of Solids, Nöthnitzer Str. 40, D-01187 Dresden, Germany.
authors.forename: Y
authors.initials: Y
authors.lastname: Drees
authors.affiliation: Max-Planck-Institute for Chemical Physics of Solids, Nöthnitzer Str. 40, D-01187 Dresden, Germany.
authors.forename: Z W
authors.initials: ZW
authors.lastname: Li
authors.affiliation: Deutsches Elektronen-Synchrotron DESY, Notkestr. 85, 22603 Hamburg, Germany.
authors.forename: A
authors.initials: A
authors.lastname: Ricci
authors.affiliation: Max-Planck-Institute for Chemical Physics of Solids, Nöthnitzer Str. 40, D-01187 Dresden, Germany.
authors.forename: M
authors.initials: M
authors.lastname: Rotter
authors.affiliation: Jülich Centre for Neutron Science JCNS, Forschungszentrum Jülich GmbH, Outstation at ILL, BP 156, 6 Rue Jules Horowitz, 38042 Grenoble, France.
authors.forename: W
authors.initials: W
authors.lastname: Schmidt
authors.affiliation: 1] Laboratoire Léon Brillouin, CEA/CNRS,F-91191 Gif-sur Yvette Cedex, UMR12 CEA-CNRS, Bât 563 CEA Saclay, France [2] Institute of Solid State Physics, Karlsruhe Institute of Technology, D-76021 Karlsruhe, Germany.
authors.forename: D
authors.initials: D
authors.lastname: Lamago
authors.affiliation: 1] Forschungsneutronenquelle Heinz Maier-Leibnitz (FRM-II), TU München, Lichtenbergstr. 1, D-85747 Garching, Germany [2] Georg-August-Universität Göttingen, Institut für Physikalische Chemie, Tammannstrasse 6, D-37077 Göttingen, Germany.
authors.forename: O
authors.initials: O
authors.lastname: Sobolev
authors.affiliation: Deutsches Elektronen-Synchrotron DESY, Notkestr. 85, 22603 Hamburg, Germany.
authors.forename: U
authors.initials: U
authors.lastname: Rütt
authors.affiliation: Deutsches Elektronen-Synchrotron DESY, Notkestr. 85, 22603 Hamburg, Germany.
authors.forename: O
authors.initials: O
authors.lastname: Gutowski
authors.affiliation: Deutsches Elektronen-Synchrotron DESY, Notkestr. 85, 22603 Hamburg, Germany.
authors.forename: M
authors.initials: M
authors.lastname: Sprung
authors.affiliation: Institut Laue-Langevin (ILL), 6 Rue Jules Horowitz, F-38043 Grenoble, France.
authors.forename: A
authors.initials: A
authors.lastname: Piovano
authors.affiliation: 1] Laboratoire Léon Brillouin, CEA/CNRS,F-91191 Gif-sur Yvette Cedex, UMR12 CEA-CNRS, Bât 563 CEA Saclay, France [2] Institute of Solid State Physics, Karlsruhe Institute of Technology, D-76021 Karlsruhe, Germany.
authors.forename: J P
authors.initials: JP
authors.lastname: Castellan
authors.affiliation: Max-Planck-Institute for Chemical Physics of Solids, Nöthnitzer Str. 40, D-01187 Dresden, Germany.
authors.forename: A C
authors.initials: AC
authors.lastname: Komarek