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All sourcesNASA NTRSDOE OSTI
DOE OSTI2020

Materials Data on Ca2RuO4 by Materials Project

Ca2RuO4 crystallizes in the orthorhombic Pbca space group. The structure is three-dimensional. Ca2+ is bonded in a 6-coordinate geometry to six O2- atoms. There are a spread of Ca–O bond distances ranging from 2.28–2.62 Å. Ru4+ is bonded to six O2- atoms to form corner-sharing RuO6 octahedra. The corner-sharing octahedral tilt angles are 30°. There are a spread of Ru–O bond distances ranging from 2.01–2.05 Å. There are two inequivalent O2- sites. In the first O2- site, O2- is bonded in a 5-coordinate geometry to three equivalent Ca2+ and two equivalent Ru4+ atoms. In the second O2- site, O2- is bonded in a distorted see-saw-like geometry to three equivalent Ca2+ and one Ru4+ atom.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Ca2RuO4 by Materials Project

Ca2RuO4 crystallizes in the orthorhombic Cmce space group. The structure is three-dimensional. Ca2+ is bonded in a 7-coordinate geometry to seven O2- atoms. There are a spread of Ca–O bond distances ranging from 2.28–2.67 Å. Ru4+ is bonded to six O2- atoms to form corner-sharing RuO6 octahedra. The corner-sharing octahedral tilt angles are 31°. There are four shorter (1.96 Å) and two longer (2.09 Å) Ru–O bond lengths. There are two inequivalent O2- sites. In the first O2- site, O2- is bonded to five equivalent Ca2+ and one Ru4+ atom to form OCa5Ru octahedra that share corners with five equivalent OCa5Ru octahedra, corners with six equivalent OCa2Ru2 tetrahedra, edges with eight equivalent OCa5Ru octahedra, and edges with four equivalent OCa2Ru2 tetrahedra. The corner-sharing octahedra tilt angles range from 0–7°. In the second O2- site, O2- is bonded to two equivalent Ca2+ and two equivalent Ru4+ atoms to form distorted OCa2Ru2 tetrahedra that share corners with six equivalent OCa5Ru octahedra, corners with six equivalent OCa2Ru2 tetrahedra, edges with four equivalent OCa5Ru octahedra, and an edgeedge with one OCa2Ru2 tetrahedra. The corner-sharing octahedra tilt angles range from 35–63°.

36 MATERIALS SCIENCE↗
DOE OSTI2023

Orbital-selective metal skin induced by alkali-metal-dosing Mott-insulating Ca2RuO4

Abstract Doped Mott insulators are the starting point for interesting physics such as high temperature superconductivity and quantum spin liquids. For multi-band Mott insulators, orbital selective ground states have been envisioned. However, orbital selective metals and Mott insulators have been difficult to realize experimentally. Here we demonstrate by photoemission spectroscopy how Ca 2 RuO 4 , upon alkali-metal surface doping, develops a single-band metal skin. Our dynamical mean field theory calculations reveal that homogeneous electron doping of Ca 2 RuO 4 results in a multi-band metal. All together, our results provide evidence for an orbital-selective Mott insulator breakdown, which is unachievable via simple electron doping. Supported by a cluster model and cluster perturbation theory calculations, we demonstrate a type of skin metal-insulator transition induced by surface dopants that orbital-selectively hybridize with the bulk Mott state and in turn produce coherent in-gap states.

Physics↗