title: Charge-transfer excitations in the model superconductor HgBa(2)CuO(4+delta).
abstract: We report a Cu -edge resonant inelastic x-ray scattering (RIXS) study of charge-transfer excitations in the 2-8 eV range in the structurally simple compound HgBa(2)CuO(4+delta) at optimal doping (T(c)=96.5 K). The spectra exhibit a significant dependence on the incident photon energy which we carefully utilize to resolve a multiplet of weakly dispersive (<0.5 eV) electron-hole excitations, including a mode at 2 eV. The observation of this 2 eV excitation suggests the existence of a remnant charge-transfer gap deep in the superconducting phase. Quite generally, our results, which include additional data for the Mott insulator La(2)CuO(4), demonstrate the importance of exploring the incident photon-energy dependence of the RIXS cross section.
authors.affiliation: Department of Applied Physics, Stanford University, Stanford, California 94305, USA.
authors.forename: L
authors.initials: L
authors.lastname: Lu
authors.forename: G
authors.initials: G
authors.lastname: Chabot-Couture
authors.forename: X
authors.initials: X
authors.lastname: Zhao
authors.forename: J N
authors.initials: JN
authors.lastname: Hancock
authors.forename: N
authors.initials: N
authors.lastname: Kaneko
authors.forename: O P
authors.initials: OP
authors.lastname: Vajk
authors.forename: G
authors.initials: G
authors.lastname: Yu
authors.forename: S
authors.initials: S
authors.lastname: Grenier
authors.forename: Y J
authors.initials: YJ
authors.lastname: Kim
authors.forename: D
authors.initials: D
authors.lastname: Casa
authors.forename: T
authors.initials: T
authors.lastname: Gog
authors.forename: M
authors.initials: M
authors.lastname: Greven