title: Nature of the Mott transition in Ca2RuO4.
abstract: We study the origin of the temperature-induced Mott transition in Ca2RuO4. As a method we use the local-density approximation+dynamical mean-field theory. We show the following. (i) The Mott transition is driven by the change in structure from long to short c-axis layered perovskite (L-Pbca→S-Pbca); it occurs together with orbital order, which follows, rather than produces, the structural transition. (ii) In the metallic L-Pbca phase the orbital polarization is ∼0. (iii) In the insulating S-Pbca phase the lower energy orbital, ∼xy, is full. (iv) The spin-flip and pair-hopping Coulomb terms reduce the effective masses in the metallic phase. Our results indicate that a similar scenario applies to Ca2-xSrxRuO4 (x≤0.2). In the metallic x≤0.5 structures electrons are progressively transferred to the xz/yz bands with increasing x; however, we find no orbital-selective Mott transition down to ∼300  K.
authors.affiliation: Institut für Festkörperforschung and Institute for Advanced Simulation, Forschungszentrum Jülich, 52425 Jülich, Germany.
authors.forename: E
authors.initials: E
authors.lastname: Gorelov
authors.forename: M
authors.initials: M
authors.lastname: Karolak
authors.forename: T O
authors.initials: TO
authors.lastname: Wehling
authors.forename: F
authors.initials: F
authors.lastname: Lechermann
authors.forename: A I
authors.initials: AI
authors.lastname: Lichtenstein
authors.forename: E
authors.initials: E
authors.lastname: Pavarini