We use resonant elastic and inelastic x-ray scattering at the Ir-L3 edge to study the doping-dependent magnetic order, magnetic excitations, and spin-orbit excitons in the electron-doped bilayer iridate (Sr1−xLax)3Ir2O7 (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 Jeff = 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 (Sr1−xLax)3Ir2O7 into a correlated metallic state with two-dimensional short range antiferromagnetic order. Strong antiferromagnetic fluctuations of the Jeff = 1/2 moments persist deep in this correlated metallic state, with the magnon gap strongly suppressed.

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Published in Physical Review Letters, v. 118, issue 2, 027202, p. 1-6.

© 2017 American Physical Society

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Xingye Lu acknowledges financial support from the European Community’s Seventh Framework Programme (FP7/2007–2013) under Grant agreement No. 290605 (COFUND: PSI-FELLOW). G. Cao acknowledges support by the US National Science Foundation via Grants No. DMR-1265162 and No. DMR-1712101. The work used Sector 27 of the Advanced Photon Source, a U.S. Department of Energy (DOE) Office of Science User Facility operated for the DOE Office of Science by Argonne National Laboratory under Contract No. DE-AC02-06CH11357.

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See Supplemental Material at http://link.aps.org/supplemental/10.1103/PhysRevLett.118.027202 for details, which includes Refs. [40–49].

PhysRevLett.118.027202_suppl.pdf (4259 kB)
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