title: Temperature dependence of crystal field excitations in CuO.
abstract: We report a study on the temperature dependence of charge-neutral crystal field (dd) excitations in cupric oxide, using nonresonant inelastic x-ray scattering spectroscopy. Thanks to a very high-energy resolution (ΔE = 60 meV), we observe thermal effects on the dd excitation spectrum fine structure between temperatures of 10-320 K. The spectra broaden considerably with increasing temperature, consistently with an enhancement of the coupling between crystal field excitations and the temperature-dependent continuum of states above the band gap. We discuss this and other mechanisms that may explain this temperature dependence.
authors.affiliation: Department of Physics, University of Helsinki, PO Box 64, FI-00014, Finland. European Synchrotron Radiation Facility, F-38043 Grenoble cedex, BP 220, France.
authors.forename: S
authors.initials: S
authors.lastname: Huotari
authors.forename: L
authors.initials: L
authors.lastname: Simonelli
authors.forename: C J
authors.initials: CJ
authors.lastname: Sahle
authors.forename: M Moretti
authors.initials: MM
authors.lastname: Sala
authors.forename: R
authors.initials: R
authors.lastname: Verbeni
authors.forename: G
authors.initials: G
authors.lastname: Monaco