title: Reversal of the lattice structure in SrCoO(x) epitaxial thin films studied by real-time optical spectroscopy and first-principles calculations.
abstract: Using real-time spectroscopic ellipsometry, we directly observed a reversible lattice and electronic structure evolution in SrCoO(x) (x=2.5-3) epitaxial thin films. Drastically different electronic ground states, which are extremely susceptible to the oxygen content x, are found in the two topotactic phases: i.e., the brownmillerite SrCoO2.5 and the perovskite SrCoO3. First-principles calculations confirmed substantial differences in the electronic structure, including a metal-insulator transition, which originate from the modification in the Co valence states and crystallographic structures. More interestingly, the two phases can be reversibly controlled by changing the ambient pressure at greatly reduced temperatures. Our finding provides an important pathway to understanding the novel oxygen-content-dependent phase transition uniquely found in multivalent transition metal oxides.
authors.affiliation: Materials Science and Technology Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, USA.
authors.forename: Woo Seok
authors.initials: WS
authors.lastname: Choi
authors.forename: Hyoungjeen
authors.initials: H
authors.lastname: Jeen
authors.forename: Jun Hee
authors.initials: JH
authors.lastname: Lee
authors.forename: S S Ambrose
authors.initials: SS
authors.lastname: Seo
authors.forename: Valentino R
authors.initials: VR
authors.lastname: Cooper
authors.forename: Karin M
authors.initials: KM
authors.lastname: Rabe
authors.forename: Ho Nyung
authors.initials: HN
authors.lastname: Lee