title: Doping Evolution of Magnetic Order and Magnetic Excitations in (Sr_{1-x}La_{x})_{3}Ir_{2}O_{7}.
abstract: We use resonant elastic and inelastic x-ray scattering at the Ir-L_{3} edge to study the doping-dependent magnetic order, magnetic excitations, and spin-orbit excitons in the electron-doped bilayer iridate (Sr_{1-x}La_{x})_{3}Ir_{2}O_{7} (0≤x≤0.065). With increasing doping x, the three-dimensional long range antiferromagnetic order is gradually suppressed and evolves into a three-dimensional short range order across the insulator-to-metal transition from x=0 to 0.05, followed by a transition to two-dimensional short range order between x=0.05 and 0.065. Because of the interactions between the J_{eff}=1/2 pseudospins and the emergent itinerant electrons, magnetic excitations undergo damping, anisotropic softening, and gap collapse, accompanied by weakly doping-dependent spin-orbit excitons. Therefore, we conclude that electron doping suppresses the magnetic anisotropy and interlayer couplings and drives (Sr_{1-x}La_{x})_{3}Ir_{2}O_{7} into a correlated metallic state with two-dimensional short range antiferromagnetic order. Strong antiferromagnetic fluctuations of the J_{eff}=1/2 moments persist deep in this correlated metallic state, with the magnon gap strongly suppressed.
authors.affiliation: Research Department Synchrotron Radiation and Nanotechnology, Paul Scherrer Institut, CH-5232 Villigen PSI, Switzerland.
authors.forename: Xingye
authors.initials: X
authors.lastname: Lu
authors.affiliation: Research Department Synchrotron Radiation and Nanotechnology, Paul Scherrer Institut, CH-5232 Villigen PSI, Switzerland.
authors.forename: D E
authors.initials: DE
authors.lastname: McNally
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: Department of Physics and Astronomy, University of Kentucky, Lexington, Kentucky 40506, USA.|Department of Physics, University of Colorado at Boulder, Boulder, Colorado 80309, USA.
authors.forename: J
authors.initials: J
authors.lastname: Terzic
authors.affiliation: Advanced Photon Source, Argonne National Laboratory, Argonne, Illinois 60439, USA.
authors.forename: M H
authors.initials: MH
authors.lastname: Upton
authors.affiliation: Advanced Photon Source, Argonne National Laboratory, Argonne, Illinois 60439, USA.
authors.forename: D
authors.initials: D
authors.lastname: Casa
authors.affiliation: Research Department Synchrotron Radiation and Nanotechnology, Paul Scherrer Institut, CH-5232 Villigen PSI, Switzerland.|SwissFEL, Paul Scherrer Institut, CH-5232 Villigen PSI, Switzerland.
authors.forename: G
authors.initials: G
authors.lastname: Ingold
authors.affiliation: Department of Physics and Astronomy, University of Kentucky, Lexington, Kentucky 40506, USA.|Department of Physics, University of Colorado at Boulder, Boulder, Colorado 80309, USA.
authors.forename: G
authors.initials: G
authors.lastname: Cao
authors.affiliation: Research Department Synchrotron Radiation and Nanotechnology, Paul Scherrer Institut, CH-5232 Villigen PSI, Switzerland.
authors.forename: T
authors.initials: T
authors.lastname: Schmitt