1. Research on High mobility oxides

We have been successful in preparing the single-phase crystal of itinerant metal oxides Sr2MoO4, which has been known to be difficult.

2. Quantum states under extreme conditions

The pressure induced ferromagnetism has been found for Ruthenate oxides.

3. Theoretical Study on Exotic Superconductivity

We have been successful to obtain the superconducting condensation energy, which is comparable to the experimental data, from the quantum variational Monte Carlo method for the 2D Hubbard model and three-band Hubabrd model.

4. List of Publications

Uranium, Ruthenates

[1] Structural, Magnetic, Transport and Thermal Properties of UCu2Sn, UPt2Sn and　UAu2Al,
T. Takabatake, H. Iwasaki, H. Fujii, S. Ikeda, S. Nishigori, Y. Aoki, T. Suzuki, and T. Fujita,
Journal of Physical Society of Japan 61, Letters, 778-781 (1992).

[2] Structural and Physical Properties of New U-T-Ga Compounds (T=Ni, Cu and Pd)
T.Takabatake, Y. Maeda, H. Fujii, S. Ikeda, S. Nishigori, T. Fujita, A. Minami,　
I. Oguro, K. Sugiyama, K. Oda, and M. Date,
Physica B186, 734-737 (1993).

[3] Specific Heat of Some Uranium-Based Ternary Compounds,
T. Fujita, S. Ikeda, S. Nishigori, Y. Aoki, T. Takabatake, and H. Fujii,
Transport and Thermal Properties of f-Electron Systems,
Edited by G.Oomi, H.Fujii, and T. Fujita, (Plenum Press, New York, 1993), p. 81-91

[4] Interplay between Kondo Effect and RKKY Interaction in UCu3+xGa2−x ,
S. Ikeda, S. Nishigori, T. Suzuki, T. Fujita, Y. Maeda, T. Takabatake, and H. Fujii,
Physica B 194-196, 465-466 (1994).

[5] Sr2CaRu2Oy : A New Phase of Layered Perovskite,
S. Ikeda, Y. Maeno, M. Nohara, and T. Fujita, Physica C 263, 558-561 (1996).

[6] Normal-State and Superconducting Properties of Sr2RuO4,
Y.Maeno, S.Nishizaki, K.Yoshida, S.Ikeda, and T.Fujita,
Journal of Low Temperature Physics 105, 1577-1586 (1996).

[7] Crossover from 3D to 2D Metallic Conduction in Sr2RuO4,
K.Yoshida, Y.Maeno, S.Nishizaki, S.Ikeda, and T.Fujita,
Journal of Low Temperature Physics 105, 1593-1598 (1996).<

[8] Two Distinct Structural Phases in Sr3-xCaxRu2Oy,
S.Ikeda, Y.Maeno, H.Muranishi, and T.Fujita,
Journal of Low Temperature Physics 105, 1599-1604 (1996).

[9] Ru NMR and NQR Studies in Superconducting Sr2RuO4 with Tc = 0.7 K,
K.Ishida, Y.Kitaoka, K.Asayama, S.Ikeda, Y.Maeno and T.Fujita,
Czechoslovak Journal of Physics 46, S2, 1093-1094 (1996).

[10] Noncuprate Layered Perovskite Superconductor,
Y.Maeno and S.Ikeda,
in "High-Tc Superconductivity 1996: Ten Years after the Discovery,"
E. Kaldis et al. (eds.) (Kluwer Academic Publishers, the Netherlands, 1997) pp. 221-242.

[11] Spin Fluctuation and Unconventional Pairing in Sr2RuO4,
Y. Kitaoka, K.Ishida, K.Asayama, S.Ikeda, S.Nishizaki, Y.Maeno, K.Yoshida and T.Fujita,
Physica C 282-287, 210-213 (1997).

[12] New layered Perovskite Ruthenates: Ca2RuO4,
S. Nakatsuji, S.Ikeda and Y.Maeno,
Physica C 282-287, 729-730 (1997).

[13] Anisotropic Pairing in Superconducting Sr2RuO4 (Tc〜0.7 K),
K. Ishida, Y.Kitaoka, K.Asayama, S.Ikeda, S.Nishizaki, Y.Maeno, K.Yoshida and T.Fujita,
Physica C 282-287, 1369-1370 (1997).

[14] Pairing Symmetry of Superconducting Sr2RuO4 from Specific Heat Measurements,
S. Nishizaki, Y.Maeno, S.Farner, S.Ikeda and T.Fujita,
Physica C 282-287, 1413-1414 (1997).

[15] Two-Dimensional Fermi-Liquid Behavior of the Superconductor Sr2RuO4,
Y.Maeno, K.Yoshida, H.Hashimoto, S.Nishizaki, S.Ikeda, M.Nohara, T.Fujita,　
A.P.Mackenzie, N.E.Hussey, J.G.Bednorz and F.Lichtenberg,
Journal of Physical Society of Japan 66, 1405-1408 (1997).

[16] Ca2RuO4: New Mott Insulators of Layered Ruthenate,
S. Nakatsuji, S.Ikeda and Y.Maeno,
Journal of Physical Society of Japan 66, Letters, 1868-1871 (1997).

[17] Anisotropic Pairing in Superconducting Sr2RuO4: Ru NMR and NQR Studies,
K.Ishida, Y.Kitaoka, K.Asayama, S.Ikeda, S.Nishizaki, Y.Maeno, K.Yoshida and T.Fujita,
Physical Review B56, Rapid Communication, 505-508 (1997).

[18] Crystallographic Features of Sr3-xCaxRu2Oy,
Y.Inoue, M.Hara, Y.Koyama, S.Ikeda, Y.Maeno and T.Fujita,
in Advances in Superconductivity IX, S. Nakajima and M. Murakami (eds.)
(Springer-Verlag, Tokyo, 1997) 281-284.

[19] Weak ferromagnetism in two-dimensional bilayered Sr3-xCaxRu2O7,
S.Ikeda, Y.Maeno and T.Fujita,
Physical Review B 57, 978-986 (1998).

[20] Thermal expansion and compressibility of Sr2RuO4,
O. Chmaissem, J. D. Jorgensen, H. Shaked, S. Ikeda, and Y. Maeno, Physical Review B57, 5067-5070 (1998).

[21] The Fermi Surface Topography of Sr2RuO4,
A.P. Mackenzie, S.Ikeda, Y.Maeno and T.Fujita, S. R. Julian, and G. G. Lonzarich,
Journal of Physical Society of Japan 67, Letters, 385-388 (1998).

[22] Evidence for Unconventional Superconductivity of Sr2RuO4 from Specific-Heat Measurements,
S. Nishizaki, Y.Maeno, S.Farner, S.Ikeda, and T.Fujita,
Journal of Physical Society of Japan 67, 560-563 (1998).

[23] Normal and Superconducting States of Sr2RuO4 as Investigated by Transport Properties (in Japanese),
N. Shirakawa et al.
Bulletin of Electrotech. Lab. 62 51 (1998).

[24] Pressure Effect on Superconductivity and Normal State of Sr2RuO4,
N. Shirakawa et al.
The Review of High Pressure Science and Technology 7,
Proceeding of International Conference -AIRAPT-16 and HPCJ-38- on High Pressure Science and Technology, 499 (1998).

[25] Pressure Dependence of Superconducting Critical Temperature of Sr2RuO4,
N. Shirakawa et al.
Phys. Rev. B 56 7890 (1997) .

[26] Novel Hall-Coefficient Behavior in Superconducting Sr2RuO4,
N. Shirakawa et al.
J. Phys. Soc. Jpn. 64 1072 (1995).

Mo Perovskites, CaVO3

[27] An Improved Method for Obtaining Single-Phase Sr2MoO4 under Controlled Ultralow Oxygen Partial Pressure,
N. Shirakawa, S. Ikeda, H. Matsuhata and H. Bando,
Jpn. J. Appl. Phys. (2001).

[28] The synthesis and basic physical properties of a layered molybdenum perovskite Sr2MoO4,
N. Shirakawa et al.
to be published in Physica C.

[29] Phase-relations study of Sr-Mo-O system for new superconductors search,
N. Shirakawa et al.
Physica C 341-348 783 (2000).

[30] Scaling of Negative Magnetoresistance and Extraordinary Hall Effect in CaVO3-d,
N. Shirakawa et al.
J. Phys. Soc. Jpn. 64 4824 (1995).

[31] Effects of Oxygen Vacancy on the Structure and Physical Properties of CaVO3-d,
N. Shirakawa et al.
Bulletin of Electrotech. Lab. 59 471 (1995).

[32] Anomalous Diamagnetism of a Perovskite LaVO3,
N. Shirakawa et al.
Jpn. J. Appl. Phys. 30 L755 (1991).

Theoretical Study

[33] Variational Monte Carlo Indications of d-Wave Superconductivity in the Two-Dimensional Hubbard Model
T. Nakanishi, K. Yamaji and T. Yanagisawa
J. Phys. Soc. Jpn. 66 (1997) 294.

[34] Variational Monte Carlo Study on the Superconductivity in the Two-Dimensional Hubbard Model
K. Yamaji, T. Yanagisawa, T. Nakanishi and S. Koike
Physica C304 (1998) 225

[35] Off-Diagonal Wave Function Monte Carlo Studies of Hubbard Model I
T. Yanagisawa, S. Koike and K. Yamaji
J. Phys. Soc. Jpn. 67 (1998) 3867

[36] Exact-diagonalization study in the effect of the long-range Coulomb interaction to the superconducting ground state in two-chain Hubbard model
S. Koike, K. Yamaji and T. Yanagisawa
Physica C308 (1998) 301

[37] Restoration of Superconductivity in High Parallel Magnetc Fields in Layered Superconductors
A.G. Lebed and K. Yamaji
Phys. Rev. Lett. 80, 2697-2700 (1998)

[38] A structure in a phonon spectral function induced by superconductivity
Y. Tanaka, K. Tokiwa, T. Itoh, E. Harashima, K. Tanaka, A. Iyo, H. Ihara, N. Terada, T.Takimoto, K. Yamaji, H. Bando and S.K. Agarwal
Physica C307 (1998) 327-334

[39] Superconductivity of Quasi-One- and Quasi-Two-Dimensional Tight-Binding Electrons in a Magnetic Field
Mitake Miyazaki, K. Kishigi and Y. Hasegawa
J. Phys. Soc. Japan 67 (1999) 2618-2621

[40] Wave functions of correlated electron state in the periodic Anderson model
T. Yanagisawa
J. Phys. Soc. Japan 68 (1999) 893

[41] Effect of the Medium-Range Transfer Energies to the Superconductivity in the Two-Chain Hubbard Model
Authors: S. Koike, K. Yamaji and T. Yanagisawa
Journal: J. Phys. Soc. Japan 68 (1999) 1657

[42] d-wave state with multiplicative correlation factors for the Hubbard model
Authors: T. Yanagisawa, S. Koike and K. Yamaji
Journal: J. Phys. Soc. Japan 68 (1999) 3608

[43] Possible Spin-Singlet Superconductivity in (TMTSF)2X
Authors: Mitake Miyazaki, K. Kishigi and Y. Hasegawa
Journal: J. Phys. Soc. Japan 68 (1999) 3794-3797

[44] Phase diagram of the CuO model in the oxide superconductors - Variational Monte Carlo study -
Authors: T. Yanagisawa, S. Koike and K. Yamaji
Journal: Physica B284 (2000) 467

[45] Numerical study of superconductivity in the two-chain Hubbard model
Authors: S. Koike, K. Yamaji and T. Yanagisawa
Journal: Physica B284 (2000) 417

[46] Bulk limit of superconducting condensation energy in 2D Hubbard model
Authors: K. Yamaji, T. Yanagisawa and S. Koike
Journal: Physica B284 (2000) 415

[47] SDW and d-Wave States in the CuO2 Model by Variational Monte Carlo Simulations
Authors: T. Yanagisawa, S. Koike and K. Yamaji
Journal: Physica B281 (2000) 933

[48] Superconducting condensation energy of the two-chain Hubbard model in the bulk limit
Authors: S. Koike, K. Yamaji and T. Yanagisawa
Journal: J. Phys. Soc. Jpn. 69, 2199-2208 (2000)

[49] Stripes and Phase Diagram of d-p Model
Authors: T. Yanagisawa, S. Koike and K. Yamaji
Journal: Physics in Local Lattice Distortions edited by A. Bianconi and H. Oyanagi (AIP, New York, 2001) p.232

[50] Competition between Supeconductivity and SDW in the 2D Hubbard Model and Possibility of Superconductivity along aStripe
Authors: K. Yamaji, T. Yanagisawa, S. Koike and M. Miyazaki
Journal: Physics in Local Lattice Distortions edited by A. Bianconi and H. Oyanagi (AIP, New York, 2001) p.222

[51] Supeconductivity of the 2D Hubbard Model with a small U
Authors: Jun Kondo
Journal: Bulletin of Electrotechnical Laboratory: 64, 67 (2000)
J. Phys. Soc. jpn. 70, 808 (2001)

[52] Superconducting and SDW condensation energies in the 2D Hubbard model and the meaning to the stripe phase
Authors: K. Yamaji, T. Yanagisawa, S. Koike
Journal: Journal of Physics and Chemistry of Solids 62, 237-241 (2001)

[53] Coexistence States of Charge Density Waves and Spin Density Waves in the One-Dimensional Extended Hubbard Model for the Arbitrary Electron Filling
Authors: K. Kishigi
Journal: Journal of the Physical Society of Japan 70 ,784 (2001).

Band Structure Calculations

[54] Electronic Structure of BaNiS2 and BaCoS2,
I. Hase, N. Shirakawa and Y. Nishihara,
J. Phys. Soc. Jpn. 64 (1995) 2533.

[55] Electronic Structure of Sr2RuO4 and Sr2RhO4,
I. Hase and Y. Nishihara,
J. Phys. Soc. Jpn. 65 (1996) 3957.

[56] Electronic Structure of Sr3Ru2O7,
I. Hase and Y. Nishihara,
J. Phys. Soc. Jpn. 66 (1997) 3517.

[57] Electronic Structure of Superconducting Layered Perovskite Niobate
I. Hase and Y. Nishihara,
Phys. Rev. B. 58 (1998) R1707.

[58] Electronic Structure of superconducting layered zirconium and hafnium nitride,
I. Hase and Y. Nishihara,
Phys. Rev. B. 60 (1999) 1573.