title: Persistent spin excitations in doped antiferromagnets revealed by resonant inelastic light scattering.
abstract: How coherent quasiparticles emerge by doping quantum antiferromagnets is a key question in correlated electron systems, whose resolution is needed to elucidate the phase diagram of copper oxides. Recent resonant inelastic X-ray scattering (RIXS) experiments in hole-doped cuprates have purported to measure high-energy collective spin excitations that persist well into the overdoped regime and bear a striking resemblance to those found in the parent compound, challenging the perception that spin excitations should weaken with doping and have a diminishing effect on superconductivity. Here we show that RIXS at the Cu L3-edge indeed provides access to the spin dynamical structure factor once one considers the full influence of light polarization. Further we demonstrate that high-energy spin excitations do not correlate with the doping dependence of Tc, while low-energy excitations depend sensitively on doping and show ferromagnetic correlations. This suggests that high-energy spin excitations are marginal to pairing in cuprate superconductors.
authors.affiliation: 1] Stanford Institute for Materials and Energy Sciences, SLAC National Accelerator Laboratory and Stanford University, Menlo Park, California 94025, USA [2] Department of Applied Physics, Stanford University, Stanford, California 94305, USA.
authors.forename: C J
authors.initials: CJ
authors.lastname: Jia
authors.affiliation: 1] Stanford Institute for Materials and Energy Sciences, SLAC National Accelerator Laboratory and Stanford University, Menlo Park, California 94025, USA [2] Department of Physics, Stanford University, Stanford, California 94305, USA.
authors.forename: E A
authors.initials: EA
authors.lastname: Nowadnick
authors.affiliation: Stanford Institute for Materials and Energy Sciences, SLAC National Accelerator Laboratory and Stanford University, Menlo Park, California 94025, USA.
authors.forename: K
authors.initials: K
authors.lastname: Wohlfeld
authors.affiliation: 1] Stanford Institute for Materials and Energy Sciences, SLAC National Accelerator Laboratory and Stanford University, Menlo Park, California 94025, USA [2] Department of Physics, Stanford University, Stanford, California 94305, USA.
authors.forename: Y F
authors.initials: YF
authors.lastname: Kung
authors.affiliation: Advanced Photon Source, Argonne National Laboratory, Lemont, Illinois 60439, USA.
authors.forename: C-C
authors.initials: CC
authors.lastname: Chen
authors.affiliation: 1] Department of Physics and Astronomy, University of British Columbia, Vancouver, British Columbia, Canada V6T 1Z1 [2] Quantum Matter Institute, University of British Columbia, Vancouver, British Columbia, Canada V6T 1Z4.
authors.forename: S
authors.initials: S
authors.lastname: Johnston
authors.affiliation: Yukawa Institute for Theoretical Physics, Kyoto University, Kyoto 606-8502, Japan.
authors.forename: T
authors.initials: T
authors.lastname: Tohyama
authors.affiliation: 1] Stanford Institute for Materials and Energy Sciences, SLAC National Accelerator Laboratory and Stanford University, Menlo Park, California 94025, USA [2] Department of Physics and Astrophysics, University of North Dakota, Grand Forks, North Dakota 58202, USA.
authors.forename: B
authors.initials: B
authors.lastname: Moritz
authors.affiliation: Stanford Institute for Materials and Energy Sciences, SLAC National Accelerator Laboratory and Stanford University, Menlo Park, California 94025, USA.
authors.forename: T P
authors.initials: TP
authors.lastname: Devereaux