Our group’s research is focused on the exploratory synthesis and characterization of strongly correlated transition-metal compounds, which exhibit novel quantum phenomena such as superconductivity, magnetic order, and a metal-insulator transition. We synthesize high-quality transition-metal compounds using a variety of techniques such as the flux, chemical vapor transport, and high-pressure methods. The electrical, magnetic, thermal, and optical properties of these compounds are then characterized on a microscopic scale. To investigate their crystal and magnetic structure, x-ray and neutron diffraction measurements are also carried out at external facilities such as SPring 8. Our recent achievements includes (1) identification of the novel magnetic order and a metal-insulator transition in strongly spin-orbit coupled iridates, (2) discovery of a new superconductor, HgxReO3, which exhibits strong rattling motion of the Hg atoms, (3) observation of second harmonic generation in non-centrosymmetric metals, (4) elucidation of the Hall effect in the Fe-based high-temperature superconductor Ba1-xKxFe2As2, and (5) clarification of the electronic properties of Fe-based ladder compounds.
Single crystals of correlated transition-metal compounds. Strongly spin-orbit coupled Mott insulator CaIrO3, Fe-based high-temperature superconductor Ba1-xKxFe2As2, non-centrosymmetric metal Pb2Ru2O7, and anomalous antiferromagnet Mn2SiS4.
Electronic phase diagram for Ca1-xNaxIrO3. Inset is a schematic view of a spin-orbit coupled electron.
Complex orbital state stabilized by strong spin-orbit coupling in a metallic iridium oxide IrO2: Y. Hirata, K. Ohgushi, J.-I. Yamaura, H. Ohsumi, S. Takeshita, M. Takata and T. Arima, Phys. Rev. B87 (2013) 161111.
Magnetoelasticity in ACr2O4 spinel oxides (A = Mn, Fe, Co, Ni, and Cu): V. Kocsis, S. Bordács, D. Varjas, K. Penc, A. Abouelsayed, C. A. Kuntscher, K. Ohgushi, Y. Tokura and I. Kézsmárki, Phys. Rev. B87 (2013) 064416.
*Mechanism of Enhanced Optical Second-Harmonic Generation in the Conducting Pyrochlore-Type Pb2Ir2O7-x Oxide Compound: Y. Hirata, M. Nakajima, Y. Nomura, H. Tajima, Y. Matsushita, K. Asoh, Y. Kiuchi, A. G. Eguiluz, R. Arita, T. Suemoto and K. Ohgushi, Phys. Rev. Lett.110 (2013) 187402.
†Suppression of Intersite Charge Transfer in Charge-Disproportionated Perovskite YCu3Fe4O12: H. Etani, I. Yamada, K. Ohgushi, N. Hayashi, Y. Kusano, M. Mizumaki, J. Kim, N. Tsuji, R. Takahashi, N. Nishiyama, T. Inoue, T. Irifune and M. Takano, J. Am. Chem. Soc.135 (2013) 6100-6106.