title: Persistent Paramagnons Deep in the Metallic Phase of Sr_{2-x}La_{x}IrO_{4}.
abstract: We have studied the magnetic excitations of electron-doped Sr_{2-x}La_{x}IrO_{4} (0≤x≤0.10) using resonant inelastic x-ray scattering at the Ir L_{3} edge. The long-range magnetic order is rapidly lost with increasing x, but two-dimensional short-range order (SRO) and dispersive magnon excitations with nearly undiminished spectral weight persist well into the metallic part of the phase diagram. The magnons in the SRO phase are heavily damped and exhibit anisotropic softening. Their dispersions are well described by a pseudospin-1/2 Heisenberg model with exchange interactions whose spatial range increases with doping. We also find a doping-independent high-energy magnetic continuum, which is not described by this model. The spin-orbit excitons arising from the pseudospin-3/2 manifold of the Ir ions broaden substantially in the SRO phase, but remain largely separated from the low-energy magnons. Pseudospin-1/2 models are therefore a good starting point for the theoretical description of the low-energy magnetic dynamics of doped iridates.
authors.affiliation: Max-Planck-Institut für Festkörperforschung, Heisenbergstr. 1, D-70569 Stuttgart, Germany.
authors.forename: H
authors.initials: H
authors.lastname: Gretarsson
authors.affiliation: Max-Planck-Institut für Festkörperforschung, Heisenbergstr. 1, D-70569 Stuttgart, Germany.
authors.forename: N H
authors.initials: NH
authors.lastname: Sung
authors.affiliation: Max-Planck-Institut für Festkörperforschung, Heisenbergstr. 1, D-70569 Stuttgart, Germany.
authors.forename: J
authors.initials: J
authors.lastname: Porras
authors.affiliation: Max-Planck-Institut für Festkörperforschung, Heisenbergstr. 1, D-70569 Stuttgart, Germany.
authors.forename: J
authors.initials: J
authors.lastname: Bertinshaw
authors.affiliation: Max-Planck-Institut für Festkörperforschung, Heisenbergstr. 1, D-70569 Stuttgart, Germany.
authors.forename: C
authors.initials: C
authors.lastname: Dietl
authors.affiliation: Max-Planck-Institut für Festkörperforschung, Heisenbergstr. 1, D-70569 Stuttgart, Germany.
authors.forename: Jan A N
authors.initials: JA
authors.lastname: Bruin
authors.affiliation: Max-Planck-Institut für Festkörperforschung, Heisenbergstr. 1, D-70569 Stuttgart, Germany.
authors.forename: A F
authors.initials: AF
authors.lastname: Bangura
authors.affiliation: Advanced Light Source, Lawrence Berkeley National Laboratory, Berkeley, California 94720, USA.|Center for Correlated Electron Systems, Institute for Basic Science, Seoul 151-742, South Korea.|Department of Physics and Astronomy, Seoul National University, Seoul 151-747, South Korea.
authors.forename: Y K
authors.initials: YK
authors.lastname: Kim
authors.affiliation: Max-Planck-Institut für Festkörperforschung, Heisenbergstr. 1, D-70569 Stuttgart, Germany.
authors.forename: R
authors.initials: R
authors.lastname: Dinnebier
authors.affiliation: Advanced Photon Source, Argonne National Laboratory, Argonne, Illinois 60439, USA.
authors.forename: Jungho
authors.initials: J
authors.lastname: Kim
authors.affiliation: European Synchrotron Radiation Facility, BP 220, F-38043 Grenoble Cedex, France.
authors.forename: A
authors.initials: A
authors.lastname: Al-Zein
authors.affiliation: European Synchrotron Radiation Facility, BP 220, F-38043 Grenoble Cedex, France.
authors.forename: M
authors.initials: M
authors.lastname: Moretti Sala
authors.affiliation: European Synchrotron Radiation Facility, BP 220, F-38043 Grenoble Cedex, France.
authors.forename: M
authors.initials: M
authors.lastname: Krisch
authors.affiliation: Max-Planck-Institut für Festkörperforschung, Heisenbergstr. 1, D-70569 Stuttgart, Germany.|Karlsruher Institut für Technologie, Institut für Festkörperphysik, Hermann-v.-Helmholtz-Platz 1, D-76344 Eggenstein-Leopoldshafen, Germany.
authors.forename: M
authors.initials: M
authors.lastname: Le Tacon
authors.affiliation: Max-Planck-Institut für Festkörperforschung, Heisenbergstr. 1, D-70569 Stuttgart, Germany.
authors.forename: B
authors.initials: B
authors.lastname: Keimer
authors.affiliation: Max-Planck-Institut für Festkörperforschung, Heisenbergstr. 1, D-70569 Stuttgart, Germany.
authors.forename: B J
authors.initials: BJ
authors.lastname: Kim