Okazaki Laboratory is a condensed matter physics research group in Tokyo University of Science founded in 2015. Our group studies exotic electronic properties emerged in the strongly correlated electron systems including oxides, organic salt and rare-earth compounds. We also focus on the electron transport behavior under illuminations or in high electric fields to examine non-equilibrium nature of correlated electrons.
伊藤さん（M2）の研究成果がPhysical Review B誌に出版されました。 Transport study on the thermoelectric oxide KxRhO2 is published in Physical Review B.
イリジウム酸化物BaIrO3の光学伝導度に関する論文が出版されました。 Optical conductivity study on unusual insulating phases of BaIrO3 is published in Physical Review B.
第3回アジア熱電国際会議（ACT3）に伊藤さん（M2）と栗田君（M1）が参加しました。 The 3rd Asian Conference on Thermoelectrics (ACT3) in Taiwan.
Temperature gradient applied in a material generates the thermoelectric voltage, known as the Seebeck effect. We study anomalous Seebeck effect in transition-metal oxides due to an entangled spin and orbital degrees of freedom in correlated electrons.
Nonlinear conduction in correlated electron systems
Correlated insulators such as charge order and Mott insulators show characteristic non-Ohmic response in the high-field range. We explore such a non-equilibrium aspect of correlated carriers by utilizing transport and thermodynamic measurements under currents.
Infrared spectroscopy is a powerful probe to grasp the electronic structure in the broad energy range. We apply this technique to the correlated electron systems, and also utilize the spatially-resolved "imaging" measurements to study the inhomogeneous electronic state.
Enhancement of low-temperature Seebeck coefficient in KxRhO2
Layered cobaltite NaxCoO2 is a well-known thermoelectric oxide. We examine the transport properties of the isovalent KxRhO2, and find an unusual enhancement of the Seebeck coefficient at a critical K content.
R. Okazaki, K. Kobayashi, R. Kumai, H. Nakao, Y. Murakami, F. Nakamura, H. Taniguchi, and I. Terasaki
"Current-induced giant lattice deformation in the Mott insulator Ca2RuO4"
N. Ito, M. Ishii, and R. Okazaki
"Enhanced Seebeck coefficient by a filling-induced Lifshitz transition in KxRhO2" Physical Review B99, 041112(R) (2019). 10.1103/PhysRevB.99.041112 arXiv:1901.02116
Published 16 January 2019
R. Okazaki, S. Ito, K. Tanabe, H. Taniguchi, Y. Ikemoto, T. Moriwaki, and I. Terasaki
"Spectroscopic signature of trimer Mott insulator and charge disproportionation in BaIrO3" Physical Review B98, 205131 (2018). 10.1103/PhysRevB.98.205131 arXiv:1811.00219
Published 16 November 2018
K. Tomiyasu, N. Ito, R. Okazaki, Y. Takahashi, M. Onodera, K. Iwasa, T. Nojima, T. Aoyama, K. Ohgushi, Y. Ishikawa, T. Kamiyama, S. Ohira-Kawamura, M. Kofu, and S. Ishihara
"Quantum Paramagnet Near Spin‐State Transition" Advanced Quantum Technologies1, 1800057 (2018). 10.1002/qute.201800057 arXiv:1712.09169
Published 7 October 2018
H. Takahashi, S. Ishiwata, R. Okazaki, Y. Yasui, and I. Terasaki
"Enhanced thermopower via spin-state modification" Physical Review B98, 024405 (2018). 10.1103/PhysRevB.98.024405 arXiv:1807.00551
Published 5 July 2018
Takaaki Sudayama, Hironori Nakao, Yuichi Yamasaki, Youichi Murakami, Shinichiro Asai, Ryuji Okazaki, Yukio Yasui, and Ichiro Terasaki
"Spin State of Co3+ in LaCo1-xRhxO3 Studied Using X-ray Absorption Spectroscopy"
J. Phys. Soc. Jpn. 86, 094701 (2017). 10.7566/JPSJ.86.094701
Published 28 July 2017
T. Okamura, R. Okazaki, H. Taniguchi, Y. Yasui, and I. Terasaki
"Magnetoelectric coupling in the pyrochlore ruthenate Gd2Ru2O7"
J. Phys. Soc. Jpn. 86, 084708 (2017). 10.7566/JPSJ.86.084708
Published 24 July 2017
N. Murashige, F. Takei, K. Saito, and R. Okazaki
"Nonlinear transport associated with spin density wave dynamics in Ca3Co4O9"
Phys. Rev. B 96, 035126 (2017). 10.1103/PhysRevB.96.035126 arXiv:1706.10088
Published 14 July 2017
I. Terasaki, S. Asai, H. Taniguchi, R. Okazaki, Y. Yasui, Y. Ikemoto, and T. Moriwaki
"Optical evidence for the spin-state disorder in LaCo1-xRhxO3"
J. Phys.: Condens. Matter 29, 235802 (2017). 10.1088/1361-648X/aa6ebc
Published 12 May 2017
T. Nagai, H. Takahashi, R. Okazaki, K. Tanabe, I. Terasaki, and H. Taniguchi
"Optical Control of Dielectric Permittivity in LaAl0.99Zn0.01O3-δ"
Appl. Phys. Lett. 110, 172901 (2017). 10.1063/1.4979644
Published 25 April 2017 *Featured in AIP Publishing: "Light Has New Capacity for Electronics"
"Transport properties of Ca2RuO4 under DC current"
日本物理学会2018年年次大会, 22pK103-7, 東京理科大学, 2018年3月22日
K. Saito and R. Okazaki
"Electron correlation effect in the thermoelectric oxide Ca3-xSrxCo4O9 single crystals"
Jpn. J. Appl. Phys. 56, 043201 (2017). 10.7567/JJAP.56.043201
Published 27 March 2017
H. Takahashi, R. Okazaki, S. Ishiwata, H. Taniguchi, A. Okutani, M. Hagiwara, and I. Terasaki
"Colossal Seebeck effect enhanced by quasi-ballistic phonons dragging massive electrons in FeSb2"
Nature Commun. 7, 12732 (2016). 10.1038/ncomms12732
Published 6 September 2016
Y. Ikeda, K. Saito, and R. Okazaki
"Thermoelectric transport in the layered Ca3Co4-xRhxO9 single crystals"
J. Appl. Phys. 119, 225105 (2016). 10.1063/1.4953359 arXiv:1605.07682
Published 8 June 2016
H. Taniguchi, T. Nakane, T. Nagai, C. Moriyoshi, Y. Kuroiwa, A. Kuwabara, M. Mizumiki, K. Nitta, R. Okazaki, and I. Terasaki
"Heterovalent Pb-Substitution of Ferroelectric Bismuth Silicate Bi2SiO5"
J. Mater. Chem. C 4, 3168 (2016). 10.1039/C6TC00584E
Published 21 April 2016
T. D. Yamamoto, R. Yatagai, K. Tanabe, R. Okazaki, H. Taniguchi, Y. Yasui, S. Iguchi, T. Sasaki, and I. Terasaki
"Enhanced thermopower and ferromagnetic fluctuations in Sc-substituted CaRuO3: An experimental study of the Kelvin formula"
APS March Meeting 2017, New Orleans, March 15, 2017