title: Nearly free electrons in a 5d delafossite oxide metal.
abstract: Understanding the role of electron correlations in strong spin-orbit transition-metal oxides is key to the realization of numerous exotic phases including spin-orbit-assisted Mott insulators, correlated topological solids, and prospective new high-temperature superconductors. To date, most attention has been focused on the 5d iridium-based oxides. We instead consider the Pt-based delafossite oxide PtCoO2. Our transport measurements, performed on single-crystal samples etched to well-defined geometries using focused ion beam techniques, yield a room temperature resistivity of only 2.1 microhm·cm (μΩ-cm), establishing PtCoO2 as the most conductive oxide known. From angle-resolved photoemission and density functional theory, we show that the underlying Fermi surface is a single cylinder of nearly hexagonal cross-section, with very weak dispersion along k z . Despite being predominantly composed of d-orbital character, the conduction band is remarkably steep, with an average effective mass of only 1.14m e. Moreover, the sharp spectral features observed in photoemission remain well defined with little additional broadening for more than 500 meV below E F, pointing to suppressed electron-electron scattering. Together, our findings establish PtCoO2 as a model nearly-free-electron system in a 5d delafossite transition-metal oxide.
authors.affiliation: Max Planck Institute for Chemical Physics of Solids, Nöthnitzer Straße 40, 01187 Dresden, Germany.
authors.forename: Pallavi
authors.initials: P
authors.lastname: Kushwaha
authors.affiliation: Max Planck Institute for Chemical Physics of Solids, Nöthnitzer Straße 40, 01187 Dresden, Germany. ; Scottish Universities Physics Alliance, School of Physics and Astronomy, University of St. Andrews, St. Andrews, Fife KY16 9SS, UK.
authors.forename: Veronika
authors.initials: V
authors.lastname: Sunko
authors.affiliation: Laboratory for Solid State Physics, ETH Zurich, CH-8093 Zurich, Switzerland.
authors.forename: Philip J W
authors.initials: PJ
authors.lastname: Moll
authors.affiliation: Scottish Universities Physics Alliance, School of Physics and Astronomy, University of St. Andrews, St. Andrews, Fife KY16 9SS, UK.
authors.forename: Lewis
authors.initials: L
authors.lastname: Bawden
authors.affiliation: Scottish Universities Physics Alliance, School of Physics and Astronomy, University of St. Andrews, St. Andrews, Fife KY16 9SS, UK. ; Diamond Light Source, Harwell Campus, Didcot, Oxfordshire OX11 0DE, UK.
authors.forename: Jonathon M
authors.initials: JM
authors.lastname: Riley
authors.affiliation: Max Planck Institute for Chemical Physics of Solids, Nöthnitzer Straße 40, 01187 Dresden, Germany.
authors.forename: Nabhanila
authors.initials: N
authors.lastname: Nandi
authors.affiliation: Max Planck Institute for Chemical Physics of Solids, Nöthnitzer Straße 40, 01187 Dresden, Germany.
authors.forename: Helge
authors.initials: H
authors.lastname: Rosner
authors.affiliation: Max Planck Institute for Chemical Physics of Solids, Nöthnitzer Straße 40, 01187 Dresden, Germany.
authors.forename: Marcus P
authors.initials: MP
authors.lastname: Schmidt
authors.affiliation: Max Planck Institute for Chemical Physics of Solids, Nöthnitzer Straße 40, 01187 Dresden, Germany.
authors.forename: Frank
authors.initials: F
authors.lastname: Arnold
authors.affiliation: Max Planck Institute for Chemical Physics of Solids, Nöthnitzer Straße 40, 01187 Dresden, Germany.
authors.forename: Elena
authors.initials: E
authors.lastname: Hassinger
authors.affiliation: Diamond Light Source, Harwell Campus, Didcot, Oxfordshire OX11 0DE, UK.
authors.forename: Timur K
authors.initials: TK
authors.lastname: Kim
authors.affiliation: Diamond Light Source, Harwell Campus, Didcot, Oxfordshire OX11 0DE, UK.
authors.forename: Moritz
authors.initials: M
authors.lastname: Hoesch
authors.affiliation: Max Planck Institute for Chemical Physics of Solids, Nöthnitzer Straße 40, 01187 Dresden, Germany. ; Scottish Universities Physics Alliance, School of Physics and Astronomy, University of St. Andrews, St. Andrews, Fife KY16 9SS, UK.
authors.forename: Andrew P
authors.initials: AP
authors.lastname: Mackenzie
authors.affiliation: Scottish Universities Physics Alliance, School of Physics and Astronomy, University of St. Andrews, St. Andrews, Fife KY16 9SS, UK.
authors.forename: Phil D C
authors.initials: PD
authors.lastname: King
keywords: 5d metal; PtCoO2; delafossite oxide; nearly-free electrons