Organic Complex Electron Systems Research Team
Team Leader
Reizo KATO (D.Sci.)
Organic conductors have clear electronic structure constructed by π-electrons. In the organic conductors, we can easily find strongly correlated electron systems and low dimensional electronic systems. They are sensitive to external stimuli including pressure, light, magnetic field, and electric field. Molecular degrees of freedom can be sources to afford novel properties in condensed matter. And, we can enjoy a variety of chemical modifications.
Based on these characteristics, this team is trying to design and develop novel organic π-electron systems with novel properties, and to reveal their fundamental principles. And, in order to understand unique properties of π-electron systems in perspective, this team is also studying 5d transition metal oxides, which are different from 3d and 4d transition metal oxides, theoretically. Physical properties of 5d transition metal oxides are determined by the behavior of 5d electrons in the 5d transition elements. The electronic wave function of 5d atomic orbital in 5d transition metal is rather extended compared to those in 3d and 4d transition metals. Thereby, the Coulomb repulsion between electrons and the electronic kinetic energy are in a similar order in energy. At the same time, because of the wider extension of wave function, 5d electrons are affected by larger crystalline field effect due to the surrounding oxygen. Moreover, 5d transition elements have a large relativistic spin-orbit interaction, which is as large as 0.5-1.0 eV, even larger than f electron systems. Therefore, in 5d transition metal oxides, all the relevant energy scales are approximately the same, which induces a variety of unique features. Our main purpose of this project is to theoretically understand those properties of 5d transition metal oxides, and to reveal the fundamental principles of 5d electron systems.
- Molecular zero-gap conductors
- Molecular quantum spin liquid
- Charge ordering phenomena in molecular materials
- Theory of electronic states in molecular materials
- Theory of electronic states in 5d transition metal oxides
- Tajima, N., Kato, R., Sugawara, S., Nishio, Y., and Kajita, K.:
"Interband Effects of Magnetic Field on Hall Conductivity in the Multilayered Massless Dirac Fermion System α-(BEDT-TTF)2I3"
Phys. Rev. B, 85, 033401/1-4 (2012). - Itou, T., Yamashita, K., Nishiyama, M., Oyamada, A., Maegawa, S., Kubo, K., and Kato, R.:
"Nuclear Magnetic Resonance of the Inequivalent Carbon Atoms in the Organic Spin-Liquid Material EtMe3Sb[Pd(dmit)2]2"
Phys. Rev. B, 84, 094405/1-5 (2011). - Yamashita, S., Yamamoto, T., Nakazawa, Y., Tamura, M., and Kato, R.:
"Gapless Spin Liquid of an Organic Triangular Compound Evidenced by Thermodynamic Measurements"
Nature Communications, 2, 275/1-6 (2011). - Kanoda, K., and Kato, R.:
"Mott Physics in Organic Conductors with Triangular Lattices"
Annu. Rev. Condens. Matter Phys., 2, 167-188 (2011). - Yoshioka, H., Seo, H., and Otsuka, Y.:
"Incommensurate Antiferromagnetic Insulating state in (MDT-TS)(AuI_2)_x"
J. Phys. Soc. Jpn. 80, 123702/1-4 (2011). - Itou, T., Oyamada, A., Maegawa, S., and Kato, R.:
"Instability of a Quantum Spin Liquid in an Organic Triangular-Lattice Antiferromagnet"
Nature Physics, 6, 673-676 (2010). - Yamashita, M., Nakata, N., Senshu, Y., Nagata, M., Yamamoto, H. M., Kato, R., Shibauchi, T., and Matsuda, Y.:
"Highly Mobile Gapless Excitations in a Two-Dimensional Candidate Quantum Spin Liquid"
Science, 328(5983), 1246-1248 (2010). - Tajima, N., Sugawara, S., Kato, R., Nishio, Y., and Kajita, K.:
"Effect of the Zero-Mode Landau Level on Interlayer Magnetoresistance in Multilayer Massless Dirac Fermion Systems"
Phys. Rev. Lett., 102(17), 176403/1-4 (2009). - Itou, T., Oyamada, A., Maegawa, S., Tamura, M., and Kato, R.:
"Quantum Spin Liquid in the Spin-1/2 Triangular Antiferromagnet EtMe3Sb[Pd(dmit)2]2"
Phys. Rev. B, 77, 104413/1-5 (2008). - Tajima, N., Kato, R., and Taniguchi, H.:
"Transport Properties of an Organic Mott Insulator β'-(BEDT-TTF)2ICl2"
Europhys. Lett. 83, 27008/1-5 (2008).
Principal Investigator
- Reizo KATO
- Team Leader
Staff Scientist
- Akira FURUSAKI
- Seiji YUNOKI
- Hitoshi SEO
- Senior Research Scientist
- Yugo OSHIMA
- Senior Research Scientist