title: Raman and fluorescence characteristics of resonant inelastic X-ray scattering from doped superconducting cuprates.
abstract: Measurements of spin excitations are essential for an understanding of spin-mediated pairing for superconductivity; and resonant inelastic X-ray scattering (RIXS) provides a considerable opportunity to probe high-energy spin excitations. However, whether RIXS correctly measures the collective spin excitations of doped superconducting cuprates remains under debate. Here we demonstrate distinct Raman- and fluorescence-like RIXS excitations of Bi1.5Pb0.6Sr1.54CaCu2O(8+δ). Combining photon-energy and momentum dependent RIXS measurements with theoretical calculations using exact diagonalization provides conclusive evidence that the Raman-like RIXS excitations correspond to collective spin excitations, which are magnons in the undoped Mott insulators and evolve into paramagnons in doped superconducting compounds. In contrast, the fluorescence-like shifts are due primarily to the continuum of particle-hole excitations in the charge channel. Our results show that under the proper experimental conditions RIXS indeed can be used to probe paramagnons in doped high-Tc cuprate superconductors.
authors.affiliation: National Synchrotron Radiation Research Center, Hsinchu 30076, Taiwan.|Program of Science and Technology of Synchrotron Light Source, National Tsing Hua University, Hsinchu 30013, Taiwan.
authors.forename: H Y
authors.initials: HY
authors.lastname: Huang
authors.affiliation: SIMES, SLAC National Accelerator Laboratory, Menlo Park, California 94025, USA.
authors.forename: C J
authors.initials: CJ
authors.lastname: Jia
authors.affiliation: Department of Physics, National Tsing Hua University, Hsinchu 30013, Taiwan.
authors.forename: Z Y
authors.initials: ZY
authors.lastname: Chen
authors.affiliation: Institute of Theoretical Physics, Faculty of Physics, University of Warsaw, PL-02093 Warsaw, Poland.
authors.forename: K
authors.initials: K
authors.lastname: Wohlfeld
authors.affiliation: SIMES, SLAC National Accelerator Laboratory, Menlo Park, California 94025, USA.
authors.forename: B
authors.initials: B
authors.lastname: Moritz
authors.affiliation: SIMES, SLAC National Accelerator Laboratory, Menlo Park, California 94025, USA.
authors.forename: T P
authors.initials: TP
authors.lastname: Devereaux
authors.affiliation: National Synchrotron Radiation Research Center, Hsinchu 30076, Taiwan.
authors.forename: W B
authors.initials: WB
authors.lastname: Wu
authors.affiliation: National Synchrotron Radiation Research Center, Hsinchu 30076, Taiwan.
authors.forename: J
authors.initials: J
authors.lastname: Okamoto
authors.affiliation: SIMES, SLAC National Accelerator Laboratory, Menlo Park, California 94025, USA.
authors.forename: W S
authors.initials: WS
authors.lastname: Lee
authors.affiliation: SIMES, SLAC National Accelerator Laboratory, Menlo Park, California 94025, USA.
authors.forename: M
authors.initials: M
authors.lastname: Hashimoto
authors.affiliation: SIMES, SLAC National Accelerator Laboratory, Menlo Park, California 94025, USA.|Department of Applied Physics, Stanford University, Stanford, California 94305, USA.
authors.forename: Y
authors.initials: Y
authors.lastname: He
authors.affiliation: SIMES, SLAC National Accelerator Laboratory, Menlo Park, California 94025, USA.|Department of Applied Physics, Stanford University, Stanford, California 94305, USA.|Department of Physics, Stanford University, Stanford, California 94305, USA.
authors.forename: Z X
authors.initials: ZX
authors.lastname: Shen
authors.affiliation: Nanoelectronics Research Institute, National Institute of Advanced Industrial Science and Technology, Tsukuba, Ibaraki 305-8562, Japan.
authors.forename: Y
authors.initials: Y
authors.lastname: Yoshida
authors.affiliation: Nanoelectronics Research Institute, National Institute of Advanced Industrial Science and Technology, Tsukuba, Ibaraki 305-8562, Japan.
authors.forename: H
authors.initials: H
authors.lastname: Eisaki
authors.affiliation: Department of Physics, National Tsing Hua University, Hsinchu 30013, Taiwan.
authors.forename: C Y
authors.initials: CY
authors.lastname: Mou
authors.affiliation: National Synchrotron Radiation Research Center, Hsinchu 30076, Taiwan.
authors.forename: C T
authors.initials: CT
authors.lastname: Chen
authors.affiliation: National Synchrotron Radiation Research Center, Hsinchu 30076, Taiwan.|Department of Physics, National Tsing Hua University, Hsinchu 30013, Taiwan.
authors.forename: D J
authors.initials: DJ
authors.lastname: Huang