title: Electron and orbital correlations in Ca2-xSrxRuO4 probed by optical spectroscopy.
abstract: The optical conductivity spectra of the quasi-two-dimensional Ca2-xSrxRuO4 (0.0< or =x< or =2.0) system were investigated. In the Mott insulating state, two electron correlation-induced peaks were observed about 1.0 and 1.9 eV, which could be explained using the 3-orbital Hubbard model. The low frequency peak showed a shift toward higher frequency as temperature was lowered, indicating that electron-phonon interactions play an important role in the orbital arrangements. From the systematic analysis, it was suggested that the antiferro-orbital and the ferro-orbital ordering states could coexist.
authors.affiliation: School of Physics and Research Center for Oxide Electronics, Seoul National University, Korea.
authors.forename: J S
authors.initials: JS
authors.lastname: Lee
authors.forename: Y S
authors.initials: YS
authors.lastname: Lee
authors.forename: T W
authors.initials: TW
authors.lastname: Noh
authors.forename: S-J
authors.initials: SJ
authors.lastname: Oh
authors.forename: Jaejun
authors.initials: J
authors.lastname: Yu
authors.forename: S
authors.initials: S
authors.lastname: Nakatsuji
authors.forename: H
authors.initials: H
authors.lastname: Fukazawa
authors.forename: Y
authors.initials: Y
authors.lastname: Maeno