Kyushu Institute of Technology Academic Repository
Kyutacarは九州工業大学で生産された研究成果を オープンアクセスで提供する機関リポジトリシステムです。 Kyutacar is open-access repository of research by members of the Kyushu Institute of Technology.
Department of Physics, University of Toronto, Toronto, Ontario M5S 1A7 Canada
Department of Chemistry, University of Waterloo, Waterloo, Ontario N2L 3G1, Canada
Department of Chemistry, University of Waterloo, Waterloo, Ontario N2L 3G1, Canada
Department of Chemistry, University of Waterloo, Waterloo, Ontario N2L 3G1, Canada
Department of Earth Sciences, University of Western Ontario, London, Ontario N6A 5B7, Canada
Faculty of Engineering, Kyushu Institute of Technology, Kitakyushu 804-8550, Japan
Institute of Physics, Chinese Academy of Sciences, Beijing, 100080, China
Department of Physics, University of Saskatchewan, Saskatoon, Saskatchewan S7N 5E2, Canada
Department of Physics, University of Ottawa, Ottawa, Ontario K1N 6N5, Canada
Department of Earth Sciences, University of Western Ontario, London, Ontario N6A 5B7, Canada
Department of Physics, University of Toronto, Toronto, Ontario M5S 1A7 Canada, Canadian Institute for Advanced Research, Toronto, Ontario M5G 1Z8, Canada
Institute of Physics, Chinese Academy of Sciences, Beijing, 100080, China
Faculty of Engineering, Kyushu Institute of Technology, Kitakyushu 804-8550, Japan
Materials Science Division, Japan Synchrotron Radiation Research Institute, SPring-8, Sayo, Hyogo 679-5198, Japan
Department of Chemistry, University of Waterloo, Waterloo, Ontario N2L 3G1, Canada
抄録
Pressure-induced changes in the solid-state structures and transport properties of three oxobenzene-bridged bisdithiazolyl radicals 2 (R = H, F, Ph) over the range 0–15 GPa are described. All three materials experience compression of their π-stacked architecture, be it (i) 1D ABABAB π-stack (R = Ph), (ii) quasi-1D slipped π-stack (R = H), or (iii) 2D brick-wall π-stack (R = F). While R = H undergoes two structural phase transitions, neither of R = F, Ph display any phase change. All three radicals order as spin-canted antiferromagnets, but spin-canted ordering is lost at pressures <1.5 GPa. At room temperature, their electrical conductivity increases rapidly with pressure, and the thermal activation energy for conduction Eact is eliminated at pressures ranging from ∼3 GPa for R = F to ∼12 GPa for R = Ph, heralding formation of a highly correlated (or bad) metallic state. For R = F, H the pressure-induced Mott insulator to metal conversion has been tracked by measurements of optical conductivity at ambient temperature and electrical resistivity at low temperature. For R = F compression to 6.2 GPa leads to a quasiquadratic temperature dependence of the resistivity over the range 5–300 K, consistent with formation of a 2D Fermi liquid state. DFT band structure calculations suggest that the ease of metallization of these radicals can be ascribed to their multiorbital character. Mixing and overlap of SOMO- and LUMO-based bands affords an increased kinetic energy stabilization of the metallic state relative to a single SOMO-based band system.
The Metallic State in Neutral Radical Conductors: Dimensionality, Pressure and Multiple Orbital Effects
scunit-2018_29.pdf
(4.52MB)
