PhD Thesis

S=1 Antiferromagnetic Heisenberg Chain in a Magnetic Field, Thesis, University of Tokyo, 1992 (_m).

Refereed journals

[228]T. Sakai: EPR Theoryis for Selection Rules to Observe the Spin Gap, Applied Magnetic Resonance 52 (2021) 507-521.

[227] T. Sakai: Quantum spin nematic liquid in the S=1 antiferromagnetic chain with the biquadratic interaction, AIP Advances 11 (2021) 015306-1-4.

[226]H. Kaneyasu, Y. Enokida, T. Nomura, Y. Hasegawa, T. Sakai and M. Sigrist: Features of Chirality Generated by Paramagnetic Coupling to Magnetic Fields in the 3K-Phase of Sr2RuO4, JPS Conference Proceedings 30 (2020) 011039-1-6.

[225]Y. Ueno, T. Zenda, Y. Tachibana, K. Okamoto and T. Sakai: Magnetization Plateau of the Distorted Diamond Spin Chain, JPS Conference Proceedings 30 (2020) 011085-1-5.

[224]T. Sakai: Spin Nematic Phase of the Quantum Spin Nanotube, JPS Conference Proceedings 29 (2020) 014004-1-5.

[223]T. Zenda, Y. Tachibana, Y. Ueno, K. Okamoto and T. Sakai: Quantum Phase Transitions of the Distorted Diamond Spin Chain, JPS Conference Proceedings 30 (2020) 011084-1-5

[222]Y. Tachibana, Y. Ueno, T. Zenda, K. Okamoto and T. Sakai: Quantum Phase Transition of the Twisted Spin Tube, JPS Conference Proceedings 30 (2020) 011082-1-5

[221]K. Okamoto, T. Tonegawa, M. Kaburagi and T. Sakai: Ground-State Phase Diagram of an Anisotropic S = 1 Ferromagnetic-Antiferromagnetic Bond-Alternating Chain, JPS Conference Proceedings 30 (2020) 011024-1-6

[220]T. Sakai and K. Okamoto: Spin Nematic Liquids of the S = 1 Spin Ladder in Magnetic Field, JPS Conference Proceedings 30 (2020) 011083-1-6

[219]H. Kaneyasu, Y. Enokida, T. Nomura, Y. Hasegawa, T. Sakai and M. Sigrist: Properties of the H-T phase diagram of the 3-K phase in eutectic Sr2RuO4-Ru: Evidence for chiral superconductivity, Phys. Rev. B 100 (2019) 21451-1-9

[218]R. Yamanokuchi, K. Okamoto and T. Sakai: Field-Induced Spin Nematic Phase in the S=1  Anisotropic Spin Ladder, Proceedings of  2018 16th International Conference on Megagauss Magnetic Field Generation and Related Topics (MEGAGAUSS) (2019) 8722674-1-4

[217]H. Nakano, N. Todoroki and T. Sakai: Haldane Gaps of Large-S Heisenberg Antiferromagnetic Chains and Asymptotic Behavior, J. Phys. Soc. Jpn. 88 (2019) 114702-1-4

[216]R. Shirakami, H. Ueda, H. O. Jeschke, H. Nakano, S. Kobayashi, A. Matsuo, T. Sakai, N. Katayama, H. Sawa, K. Kindo, C. Michioka and K. Yoshimura: Two magnetization plateaus in the kagome fluoride Ce2LiTi3F, Phys. Rev. B 100 (2019) 8722674-1-4

[215]M. Fujiwara, N. Shima, K. Makoshi and T. Sakai: Analysis of Rashba Effect on Au(111) Model Surface, J. Phys. Soc. Jpn. 88 (2019), 034604-1-5

[214]H. O. Jeschke, H. Nakano and T. Sakai: From kagome strip to kagome lattice: Realizations of frustrated S=1/2 antiferromagnets in Ti(III) fluorides, Phys. Rev. B 99 (2019) 140410(R)-1-6.

[213]T. Sakai, K. Okamoto and T. Tonegawa: Magnetization plateau of the S=2 antiferromagnetic Heisenberg chain with anisotropies, Phys. Rev. B 100 (2019) 054407-1-6

[212]Y. Hasegawa, H. Nakano and T. Sakai: Metamagnetic jump in the spin-1/2 antiferromagnetic Heisenberg model on the square kagome lattice, Phys. Rev. B 98 (2018) 014404-1-9

[211]T. Sakai and H. Nakano: Ground state with nonzero spontaneous magnetization of the two-dimensional spin-1/2 Heisenberg antiferromagnet with frustration, AIP ADVANCES 8 (2018) 101408-1-5

[210]H. Nakano and T. Sakai: Third Boundary of the Shastry-Sutherland Model by Numerical Diagonalization, J. Phys. Soc. Jpn. 87 (2018), 123702-1-5

[209]T. Tonegawa, T. Hikihara, K. Okamoto, S. C. Furuya and T. Sakai: Ground-State Phase Diagram of an Anisotropic S=1/2 Ladder with Different Interactions, J. Phys. Soc. Jpn. 87 (2018) 104002-1-11

[208]H. Nakano and T. Sakai: Precise Estimation of the S=2 Haldane Gap by Numerical Diagonalization, J. Phys. Soc. Jpn. 87 (2018) 105002-1-2

[207]H. Nakano and T. Sakai: Numerical Diagonalization Study of Magnetization Process of Frustrated Spin-1/2 Heisenberg Antiferromagnets in Two Dimensions  -Triangular- and Kagome-Lattice Antiferromagnets-, J. Phys. Soc. Jpn. 87 (2018) 063706-1-5

[206]T. Sakai and H. Nakano: Gapless Spin Excitations in the S=1/2 Kagome- and Triangular-Lattice Heisenberg Antiferromagnets, Physica B 536 (2018) 85-88

[205]A. Shimada, T. Sakai, H. Nakano and K. Yoshimura: Spontaneous Magnetization of the Spin-1/2 Heisenberg Antiferromagnet on the Triangular Lattice with a Distortion,J. Phys.: Conf. Ser. 969 (2018) 012126-1-6

[204]T. Sakai and H. Nakano: Quantum Spin Fluid Behaviors of the Kagome- and Triangular-Lattice Antiferromagnets, J. Phys.: Conf. Ser. 969 (2018) 012127-1-6

[203]A. Shimada, H. Nakano, T. Sakai and K. Yoshimura: The Spin-1/2 Heisenberg Antiferromagnet on a Triangular-Lattice with 3~3-Type Distortion -Magnetization Process and Magnetic Susceptibility-, J. Jpn. Soc. Powder Powder Metallurgy 65 (2018) 3

[202]A. Shimada, H. Nakano, T. Sakai and K. Yoshimura: Spin-1/2 Triangular-Lattice Heisenberg Antiferromagnet with 3~3-Type Distortion -Behavior around the Boundaries of the Intermediate Phse-, J. Phys. Soc. Jpn. 87 (2018) 034706-1-7

[201] H. Nakano and T. Sakai: Magnetization Process of the Spin-1/2 Triangular-Lattice Heisenberg Antiferromagnet with Next-Nearest-Neighbor Interactions -Plateau or Nonplateau-, J. Phys. Soc. Jpn. 86 (2017) 114705

[200] T. Sakai and H. Nakano: Quantum Spin Liquid in the Kagome-Lattice Antiferromagnet and Related Systems, J. Phys.: Conf. Ser. 868 (2017) 012006-1-10

[199] K. Ito, S. Yokoo, K. Okamoto and T. Sakai, Quantum Phase Transition in the Twisted Three-Leg Spin Tube, POLYHEDRON 136 (2017) 42-44

[198] H. Nakano and T. Sakai, Ferrimagnetism in the Spin-1/2 Heisenberg Antiferromagnet on a Distorted Triangular Lattice, J. Phys. Soc. Jpn. 86 (2017) 063702-1-4

[197] T. Tonegawa, K. Okamoto, T. Hikihara and T. Sakai, Frustrated S=1/2 Two-Leg Ladder with Different Leg Interactions, J. Phys.: Conf. Ser. 828 (2017) 012003-1-8

[196] T. Hikihara, T. Tonegawa, K. Okamoto and T. Sakai, Exact ground states of frustrated quantum spin systems consisting of spin-dimer units, J. Phys. Soc. Jpn. 86 (2017) 054709-1-8

[195] T. Sakai and H. Nakano, Gapless Quantum Spin Liquid of the Kagome-Lattice Antiferromagnet, POLYHEDRON 126 (2017) 42-44

[194] S. Okubo, R. Nakata, S. Idehara, N. Takahashi, T. Sakurai, W. Zhang, H. Ohta, T. Shimokawa, T. Sakai, K. Okuta, S. Hara, and H. Sato, Dzyaloshinsky-Moriya Interaction and the Ground State in S=3/2 Perfect Kagome Lattice Antiferromagnet KCr3(OH)6(SO4)2 (Cr-Jarosite) Studied by X-Band and High-Frequency ESR, J. Phys. Soc. Jpn. 86 (2017) 024703-1-6

[193] K. Okamoto, T. Tonegawa and T. Sakai, Effect of monomer-monomer interactions on the phase diagrams of the S=1/2 distorted diamond type quantum spin chain, J. Phys.: Conf. Ser. 683 (2016) 012038-1-6

[192] T. Tonegawa, K. Okamoto, T. Hikihara and T. Sakai, Ground-state phase diagram of an anisotropic S=1/2 ladder with alternating rung interactions, J. Phys.: Conf. Ser. 683 (2016) 012039-1-7

[191] K. Okamoto, T. Tonegawa and T. Sakai, "Ground State Phase Diagram of the Bond-Alternating S=2 Quantum Spin Chain with the XXZ and On-Site Anisotropies -Symmetry Protected Topological Phase versus Trivial Phase-, J. Phys. Soc. Jpn. (Letters) 85 (2016) 063704-1-4

[190] T. Sakai and H. Nakano:  Exotic Field Induced Quantum Phase Transition of the Kagome Lattice Antiferromagnet, Physics Procedia 75 (2015) 821-828

[189] T. Sakai and H. Nakano: Quantum Phase Transition in the Three-Leg Spin Tube, Physics Procedia 75 (2015) 369-375

[188] H. Kaneyasu, S. B. Etter, T. Sakai and M. Sigrist: Evolution of the filamentary 3-Kelvin phase in Pb-Ru-Sr2RuO4 Josephson junction, Phys. Rev. B 92 (2015) 134515-1-5

[187] H. Nakano, Y. Hasegawa and T. Sakai: Magnetization jump in the Magnetization Process of the spin-1/2 Heisenberg Antiferromagnet on a Distorted Square-Kagome Lattice, J. Phys. Soc. Jpn. 84 (2015) 114703-1-6

[186] T. Sakai, K. Hijii, S. Okubo, H. Ohta, H. Nakano, S. Miyashita: Possible Singlet-Triplet Transition of ESR in the Kagome-Lattice Antiferromagnet, Applied Magnetic Resonance 46 (2015) 997-1002

[185] T. Sakai, T. Kasahara, K. Hijii, H. Ohta, H. Nakano: Spin nanotubes with the ring exchange interactions, Synthetic Metals 208 (2015) 26-28

[184]H. Nakano and T. Sakai: Magnetization Process of the Spin-S Kagome-Lattice Heisenberg Antiferromagnet, J. Phys. Soc. Jpn. 84 (2015) 063705-1-4

[183]H. Nakano and T. Sakai: Instability of a ferromagnetic state of a frustrated S=1/2 Heisenberg antiferromagnet in two dimensions, Jpn. J. Appl. Phys. (Rapid Communication) 54 (2015) 030305-1-4

[182]T. Sakai and H. Nakano: Novel Field Induced Quantum Phase Transition of the Kagome Lattice Antiferromagnet, J. Phys.: Conf. Ser. 568 (2014) 042025-1-6

[181]T. Sakai, H. Nakano and K. Okunishi: Exotic Quantum Phase Transition of the Spin Nanotube, J. Phys.: Conf. Ser. 568 (2014) 042024-1-5

[180]H. Nakano and T. Sakai: Anomalous Behavior of the Magnetization Process of the S=1/2 Kagome-Lattice Heisenberg Antiferromagnet at One-Third Height of the Saturation, J. Phys. Soc. Jpn. 83 (2014) 104710-1-7.

[179] M. Isoda, H. Nakano and T. Sakai: Orthogonal Dimer, Disordered, and Ferrimagnetic States in the Spin-1/2 Heisenberg Antiferromagnet on the Cairo Pentagon Lattice, J. Phys. Soc. Jpn. 83 (2014) 084710-1-7.

[178]H. Nakano, T. Sakai and Y. Hasegawa:  A Spin Flop Phenomena in the Magnetization Process of Two-Dimensional Antiferromagnets without Anisotropy in Spin Space, J. Phys. Soc. Jpn. 83 (2014) 084709-1-7

[177]H. Nakano, M. Isoda and T. Sakai: The Magnetization Process of the S=1/2 Heisenberg Antiferromagnet on the Cairo Pentagon Lattice with Distortion, J. Phys. Soc. Jpn. 83 (2014) 053702-1-4

[176] K. Watanabe, H. Kawamura, H. Nakano and T. Sakai: Quantum Spin-Liquid Behavior in the Spin-1/2 Random Heisenberg Antiferromagnet on the Triangular Lattice, J. Phys. Soc. Jpn. 83 (2014) 034714-1-6.

[175] K. Okamoto, T. Tonegawa, T. Sakai and M. Kaburagi: Edge Modes in the Intermediate-D and Large-D Phases of the S=2 Quantum Spin Chain with XXZ and On-Site Anisotropies, JPS Conf. Proc. 3 (2014) 014022-1-7

[174] H. Nakano and T. Sakai: Anomalous Quantum Magnetization Behaviors of the Kagome and , Triangular Lattice Antiferromagnets, JPS Conf. Proc. 3 (2014) 014003-1-6

[173] T. Sakai and K. Okamoto: Exotic Magnetism of the Quantum Spin Nanotube, JPS Conf. Proc. 2 (2014) 010208-1-4

[172] T. Sakai and K. Okamoto: Exotic Quantum Phenomena in the Spin Nanotubes, JPS Conf. Proc. 1 (2014) 012025-1-4

[171] K. Hijii and T. Sakai, Ground-state phase diagram of an S=1/2 two-leg Heisenberg spin ladder system with negative four-spin interaction, Phys. Rev. B 88 (2013) 104403-1-8

[170] K. Okunishi, M. Sato, T. Sakai, K. Okamoto and C. Itoi, Quantum Phase Transitions in 1/3 Plateau of the Quantum Spin Tube, J. Korean Phys. Soc. 63 (2013) 596-600

[169] H. Nakano and T. Sakai: The Two-Dimensional S=1/2 Heisenberg Antiferromagnet on the Shuriken Lattice -a Lattice Composed of Vertex-Sharing Triangles-, J.Phys. Soc. Jpn. (Letters) 82 (2013) 083709-1-4

[168]H. Nakano, S. Todo and T. Sakai: Long-Range Order of the Three-Sublattice Structure in the S=1 Heisenberg Antiferromagnet on the Spatially Anisotropic Triangular Lattice, J. Phys. Soc. Jpn. (Letters) 82 (2013) 043715-1-5

[167]T. Tonegawa, K. Okamoto and T. Sakai: Anomalous behavior of the spin gap of a spin-1/2 two-leg antiferromagnetic ladder with Ising-like rung interations, Physica Status Solidi. B250 (2013) 575-578

[166] T. Sakai and H. Nakano: Quantum Critical Magnetization Behaviors of the Kagome- and Triangular-Lattice Antiferromagnets, Physica Status Solidi. B250 (2013) 579-582

[165]T. Sakai and H. Nakano: Quantum Critical Magnetization Behaviors of the Kagome- and Triangular-Lattice Antiferromagnets, J. Low. Temperature Phys. 170 (2013) 255-260

[164]T. Sakai and H. Nakano: Novel Field-Induced Quantum Phase Transition of the Kagome-Lattice Antiferromagnet, J. Korean Phys. Soc. 63 (2013) 601-604

[163] M. Isoda, H. Nakano and T. Sakai: A Consistent Description of Magnetic Properties of the Triangulated-Kagome System Cu9X2(cpa)6EnH2O, J. Phys. Soc. Jpn. 81 (2012) 053703-1-4

[162]S. Okubo, T. Ueda, H. Ohta, W. Zhang, T. Sakurai, N. Onishi, M. Azuma, Y. Shimakawa, H. Nakano and T. Sakai: Dzyaloshinsky-Moriya interaction and field-induced magnetic order in an antiferromagnetic honeycomb lattice compound Bi3Mn4O12(NO3) studied by high-field electron spin resonance, Phys. Rev. B 86 (2012) 140401(R)-1-4

[161]K. Okunishi, M. Sato, T. Sakai, K. Okamoto and C. Itoi: Spin-Chirality Separation and S3-Symmetry Breakings in the Magnetization Plateau of the Quantum Spin Tube, Phys. Rev. B 85 (2012) 054416-1-6

[160]T. Sakai, M. Sato, K. Okunishi, K. Okamoto and C. Itoi: Exotic Quantum Phase Transitions in the Spin Nanotubes, J. Phys.: Conf. Ser. 400 (2012) 032075-1-4

[159]T. Sakai and H. Nakano: Novel Field-Induced Quantum Phase Transition of the Kagome-Lattice Antiferromagnet, J. Phys.: Conf. Ser. 400 (2012) 032076-1-4

[158]Y. Otsuka and T. Sakai: Topological Aspects of the Quantum Spin Nanotube, J. Phys.: Conf. Ser. 344 (2012) 012009-1-6

[157]T. Sakai, M. Sato, K. Okunishi, K. Okamoto and C. Itoi, Density Matrix Renormalization Group and Numerical Diagonalization Study on the Quantum Spin Nanotube in Magnetic Field, Progress in NUCLEAR SCIENCE and TECHNOLOGY Vol. 2 (2011) 30-33.

[156]T. Sakai and H. Nakano: Numerical Study on the Spin Dynamics of the Kagome Lattice Antiferromagnet, J. Phys. Soc. Jpn. 80 Supplement B (2011) SB014-1-3.

[155]M. Isoda, H. Nakano and T. Sakai: Specific Heat and Magnetic Susceptibility of Ising-like Anisotropic Heisenberg Model on Kagome Lattice, J. Phys. Soc. Jpn. 80 (2011) 084704-1-6

[154]K. Okamoto, T. Tonegawa, H. Nakano, T. Sakai, K. Nomura and M. Kaburagi, How to Distinguish the Haldane/Large-D State and the Intermediate-D State in an S=2 Quantum Spin Chain with the XXZ and On-Site Anisotropies, J. Phys.: Conf. Ser. 320 (2011) 012018-1-4

[153]M. Isoda, H. Nakano and T. Sakai: Numerical exact diagonalization study of triangulated kagome Heisenberg spin system, J. Phys.: Conf. Ser. 320 (2011) 012010-1-4

[152]S. Abe, T. Sakai, K. Okamoto and K. Tsutsui, Numerical Diagonalization Study on the S=1/2 Frustrated Three-Leg Quantum Spin Ladder Systems, J. Phys.: Conf. Ser. 320 (2011) 012015-1-4

[151]H. Nakano and T. Sakai: Magnetization ramp of the kagome lattice antiferromagnet, J. Phys.: Conf. Ser. 320 (2011) 012017-1-4

[150]T. Sakai, M. Sato, K. Okunishi, K. Okamoto and C. Itoi: Exotic quantum phase transitions in the spin nanotube, J. Phys.: Conf. Ser. 320 (2011) 012022-1-4

[149]T. Sakai and H. Nakano: Quantum critical phenomena in magnetization process of the Kagome and triangular lattice antiferromagnets, J. Phys.: Conf. Ser. 320 (2011) 012016-1-4

[148]K. Okamoto, T. Tonegawa, H. Nakano, T. Sakai, K. Nomura and M. Kaburagi: Ground-State Phase Diagram of S=2 Quantum Spin Chain with the XXZ and On-Site Anisotropies, J. Phys.: Conf. Ser. 302 (2011) 012014-1-4

[147] T. Sakai, M. Sato, K. Okunishi, K. Okamoto and C. Itoi: Exotic Quantum Critical Phenomena of the Spin Nanotubes, J. Phys.: Conf. Ser. 302 (2011) 012013-1-4

[146]M. Isoda, H. nakano and T. Sakai: Thermodynamic Properties of S=1/2 Ising-like Heisenberg on Triangule-based Lattices, Mod. Phys. Lett. B 25 (2011) 909-915.

[145]H. Nakano and T. Sakai: Numerical-Diagonalization Study on Spin Gap Issue of the Kagome Lattice Heisenberg Antiferromagnet, J. Phys. Soc. Jpn. (Letters) 80 (2011) 053704-1-4.

[144]T. Tonegawa, K. Okamoto, H. Nakano, T. Sakai, K. Nomura and M. Kaburagi: Haldane, Large-D and Intermediate-D States in an S=2 Quantum Spin Chain with On-Site and XXZ Anisotropies, J. Phys. Soc. Jpn. (Letters) 80 (2011) 043001-1-4

[143]T. Sakai and H. Nakano: Critical magnetization behavior of the triangular- and kagome-lattice quantum antiferromagnets, Phys. Rev. B 83 (2011) 100405(R)-1-4.

[142]H. Nakano, T. Shimokawa and T. Sakai: Collapse of Ferrimagnetism in Two-Dimensional Heisenberg Antiferromagnet due to Frustration, J. Phys. Soc. Jpn. (Letters) 80 (2011) 033709-1-4

[141] K. Okamoto, M. Sato, K. Okunishi, T. Sakai and C. Itoi: Magnetization Plateau of the Quantum Spin Nanotube, Physica E 43 (2011) 769-772

[140] T. Sakai, M. Sato, K. Okamoto, K. Okunishi and C. Itoi, Quantum Spin Nanotubes ---frustration, competing orders and criticalities, J. Phys.: Condens. Matter  22 (2010) 403201-1-13. (Topical review, invited).

[139] T. Sakai : Numerical Exact Diagonalization Study on a Phonon-Assisted Hole Paring in the High-Tc Cuprates, Physica C 470 (2010) S80-81

[138]H. Nakano and T. Sakai: Magnetization Process of the Kagome Lattice Antiferromagnet, J. Phys. Soc. Jpn. (Letter) 79 (2010) 053707-1-4.

[137]T. Tonegawa, K. Okamoto and T. Sakai: First-Order Phase Transition between One-Third Magnetization Plateau States in an Anisotropic (S, S') Spin Alternating Chain, Physica Status Solidi B 247 (2010) 688-690

[136]T. Sakai, T. Tonegawa and K. Okamoto: Field-Induced Nematic Phase in the Spin Ladder System with Easy-Axis Anisotropy, Physica Status Solidi B 247 (2010) 583-585.

[135]T. Tonegawa, H. Nakano, T. Sakai, K. Okamoto, K. Okunishi and K. Nomura: Half Magnetization Plateau of a Frustrated S=1 Antiferromagnetic Chain, J. Phys. Conf. Ser. 200 (2010) 022065-1-4

[134]T. Sakai, T. Tonegawa and K. Okamoto: Magnetization Process of the S=1/2 Distorted Diamond Spin Chain with the Dzyaloshinsky-Moriya interaction, J. Phys. Conf. Ser. 200 (2010) 022052-1-4

[133]T. Sakai, K. Okunishi, K. Okamoto, C. Itoi and M. Sato: Field Induced Exotic Phenomena of the S=1/2 Three-Leg Quantum Spin Nanotube, J. Low Temperature Phys. 159 (2010) 55-58

[132]K. Okunishi, S. Yoshikawa, T. Sakai and S. Miyashita: Quantum Phase Transition of a Triangular Lattice Spin Tube and Edge Spin Effects, Int. J. Mod. Phys. C 20 (2009) 1423-1430.

[131]T. Sakai, T. Tonegawa and K. Okamoto: Elementary excitations and spin dynamics in nanowire quantum magnets, Int. J. Mod. Phys. C 20 (2009) 1467-1476.

[130]Y. Yoshida, T. Kawae, Y. Hosokoshi, K. Inoue, N. Maeshima, K. Okunishi, K. Okamoto and T. Sakai: Magnetic Field versus Temperature Phase Diagram of the Spin-1/2 Alternating-Bond Chain Compound F5PNN, J. Phys. Soc. Jpn. 78 (2009) 074716-1-5.

[129]M. Fujisawa, K. Shiraki, S. Okubo, H. Ohta, M. Yoshida, H. Tanaka and T. Sakai: Dzylashinsky-Moriya Interaction in the S=1/2 Quasi-One-Dimensional Antiferromagnet Cu2Cl4EH8C4SO2 as Determined via High-Frequency ESR, Phys. Rev. B 80 (2009) 012408-1-4.

[128]M. Okumura, S. Yamada, M. Machida and T. Sakai: Polarization Plateau in Atomic Fermi Gas Loaded on Triangular Optical Lattice, Phys. Rev. A 79 (2009) 061602(R)-1-4

[127]T. Sakai, T. Tonegawa and K. Okamoto: Two-step quantum spin flop transition in spin ladders, J. Phys.: Conf. Series. 150 (2009) 042169-1-4

[126]T. Tonegawa, T. Sakai, K. Okamoto and M. Kaburagi: Ground-State Phase Diagram of an (S, Sf)=(1, 2) Spin-Alternating Chain with Competing Single-Ion Anisotropies, J. Phys.: Conf. Series. 145 (2009) 012066-1-4.

[125]T. Sakai, K. Okamoto and T. Tonegawa: Field-Induced Incommensurate Order and Possible Supersolid in the S=1/2 Frustrated Diamond Chain, J. Phys.: Conf. Series. 145 (2009) 012065-1-4

[124]T. Sakai, M. Sato, K. Okunishi, Y. Otsuka, K. Okamoto and C. Itoi: Quantum phase transitions of the asymmetric three-leg spin tube, Phys. Rev. B 78 (2008) 184415-1-11

[123]T. Sakai: Numerical Diagonalization Study on a Phonon-assisted Hole Pairing Mechanism of an Extended t-J Holstein Model,J. Phys.: Conf. Series. 108 (2008) 012026-1-4

[122]T. Sakai: Possible Mechanism of Charge Stripe Formation Based on the Ring Exchange Interaction, Physica C 468 (2008) 1163-1165

[121]T. Tonegawa, T. Sakai, K. Okamoto and M. Kaburagi: One-Third Magnetization Plateau in an Anisotropin (S,S')=(1,2) Spin-Alternating Chain, J. Phys. Soc. Jpn. 76 (2007) 124701-1-8

[120]T. Sakai: Finite-temperature simulation based on the Lanczos algorithm for low-dimensional strongly correlated electron systems; high-temperature superconducting cuprates,  Proceedigs of Mathematics and Supercomputing in Nuclear Applications, (2007) 01097-1-5

[119]T. Sakai, K. Okamoto and T. Tonegawa: Quantum Spin Flop Transition in Nanowire Ferrimagnets, Physica E 40 (2007) 359-362

[118]M. Sato and T. Sakai: Vector chirality and inhomogeneous magnetization in three-leg frustrated antiferromagnetic spin tubes in high magnetic fields, Phys. Rev. B 75 (2007) 014411-1-5

[117]K. Okamoto, A. Tokuno and T. Sakai: Interplay between the trimerization and frustration in spin-1/2 disordered diamond type spin chain with the XXZ anisotropy, J. Magn. Magn. Mat. 310 (2007) e457-e459.

[116]T. Tonegawa, K. Okamoto, K. Okunishi and T. Sakai: Finite-field ground satate of an S=1 zigzag ladder, J. Magn. Magn. Mat. 310 (2007) e372-e374

[115]T. Sakai, K. Okunishi, K. Okamoto, M. Sato, M. Matsumoto and Y. Otsuka: Quantum Phase Transition in the Three-leg Spin Nanotube, J. Magn. Magn. Mat. 310 (2007) e423-e425

[114]T. Sakai and K. Okamoto: Field-Induced Incommensurate Order in Frustrated Spin Ladder, J. Phys.: Condens. Matter 19 (2007) 145231-1-5

[113]T. Tonegawa, T. Sakai, K. Okamoto and M. Kaburagi: 1/3 magnetization plateau in a one-dimensional anisotropic ferrimagnet, J. Phys. Conf. Series. 51 (2006) 171-174.

[112]T. Sakai, T. Tonegawa and K. Okamoto: Quantum Magnetization Plateau of an Anisotropic Mixed Spin Chain, J. Phys. Conf. Series 51 (2006) 163-166.

[111]J. Kishine, T. Watanabe, H. Deguchi, M. Mito, T. Sakai, T. Tajiri, M. Yamashita and H. Miyasaka: Spin correlation and relaxation dynamics in molecular-based single-chain magnets, Phys. Rev. B 74 (2006) 224419-1-7.

[110]H. Kikuchi, Y. Fujii, M. Chiba, S. Mitsudo, T. Idehara, T. Tonegawa,K. Okamoto, T. Sakai, T. Kuwai and H. Ohta: Reply to the comment on ``Experimental Observation of the 1/3 Magnetization Plateau in a Diamond Chain Compound Cu3(CO3)2(OH)2'', Phys. Rev. Lett.   97 (2006) 089702.

[109]N. Maeshima, K. Okunishi, K. Okamoto, T. Sakai and K. Yonemitsu: Field-Induced Incommensurate Order in Frustrated Spin Chain, J. Phys.: Condens. Matter. 18 (2006) 4819-4826

[108] Y. Oshima, H. Nojiri, K. Asakura, T. Sakai, H. Miyasaka and M. Yamashita: Observation of the Collective Magnetic Excitation in the Single-Chain Magnet, Phys. Rev. B 73 (2006) 214435-1-5

[107]T. Sakai and D. Poilblanc: Polaronic effect in lightly doped high-Tc cuprates,  AIP Conf. Proc. 850 (2006) 553-554

[106]T. Sakai, K. Okamoto, K. Okunishi and T. Tonegawa: Field-induced incommensurate order in quasi-1D S=1 antiferromagnet, AIP Conf. Proc. 850 (2006) 1065-1066

[105]M. Matsumoto, T. Yamada, M. Koga, K. Okamoto and T. Sakai: Theory of Excitation Modes in Diamond Chain Compound Cu3(CO3)2(OH)2, Physica B 378-380 (2006) 1037-1038.

[104]T. Sakai, M. Matsumoto, K. Asakura and M. Sato: Elementary Excitations of Nanowire Magnets, Prog. Theor. Phys. Suppl. No. 159 (2005) 308-313.

[103]K. Okunishi, S. Yoshikawa, T. Sakai and S. Miyashita: Low-energy excitations of the S=1/2 quantum spin tube with triangular lattice structure, Prog. Theor. Phys. Suppl. No. 159 (2005) 297-301

[102]T. Tonegawa, K. Okunishi, T. Sakai and M. Kaburagi: Finite-Field Ground State of the S=1 Anisotropic Frustrated Antiferromagnetic Chain, Prog. Theor. Phys. Suppl. No. 159 (2005) 77-81.

[101]K. Okamoto, T. Tonegawa, T. Yamada, M. Matsumoto, M. Koga and T. Sakai: Ground-State Phase Diagram of the S=1/2 Distorted Diamond Type Spin Chain with Ferromagnetic Interactions, Prog. Theor. Phys. Suppl. No. 159 (2005) 17-21

[100]H. Kikuchi, Y. Fujii, M. Chiba, S. Mitsudo, T. Idehara, T. Tonegawa,K. Okamoto, T. Sakai, T. Kuwai and H. Ohta: Experimental Observation of the 1/3 Magnetization Plateau in a Diamond Chain Compound Cu3(CO3)2(OH)2, Phys. Rev. Lett.   94 (2005) 227201-1-4

[99]M. Kikuchi, K. Okamoto, K. Okunishi and T. Sakai: Magnetization Plateau of S=1 Spin Ladder BIP-TENO, Prog. Theor. Phys. No. 159 (2005) 251-255.

[98]H. Kikuchi, Y. Hujii, M. Chiba, S. Mitsudo, T. Idehara, T. Tonegawa, K. Okamoto, T. Sakai, T. Kuwai, K. Kindo, A. Matsuo, W. Higemoto, K. Nishiyama, M. Horvatic and C. Berthier: Magnetic Properties, of the Diamond Chain Compound Cu3(CO3)2(OH)2, Prog. Theor. Phys. Suppl. No. 159 (2005) 1-10.

[97]M. Matsumoto, T. Sakai, M. Sato, H. Takayama and S. Todo: Quantum phase transitions of spin chiral nanotubes, Physica E  29(2005) 660-663

[96]T. Sakai, M. Matsumoto, K. Okunishi, K. Okamoto and M. Sato: Energy Gap of Spin Nanotubes, Physica E  29 (2005) 633-636.

[95]T. Sakai and K. Okamoto: Field-Induced Incommensurate Order in Spin Ladder with Ring Exchange, J. Phys. Chem. Solid  66(2005) 1450-1453.

[94]T. Sakai and S. Yamamoto: Transport Properties of Organic Spin-Gapped Antiferromagnets, Synthetic Metals  152 (2005) 477-480.

[93]T. Sakai, Impurity Pinning of Spin Density Wave,  Prog. Theor. Phys. Suppl. No. 157 (2005) 148-151

[92]N. Maeshima, K. Okunishi, K. Okamoto, T. Sakai and K. Yonemitsu:  Frustration-Induced Enhancement of the Incommensurate Fluctuation in the S=1/2 Bond-Alternating Spin Chain, J. Phys. Soc. Jpn.  74  Suppl. (2005) 63-66

[91]K. Okamoto, K. Okunishi and T. Sakai: Magnetization Process of the S=1 frustrated Two-Leg Ladder, J. Phys. Soc. Jpn.  74  Suppl. (2005) 165-168.

[90]M. Kikuchi, K. Okunishi, K. Okamoto and T. Sakai: Bond-Alternating S=1 Spin Ladder in Magnetic Field, J. Phys. Soc. Jpn.  74 Suppl.  (2005) 169-172

[89]T. Sakai and S. Yamamoto: Transport in Gapped Quantum Antiferromagnets, Phys. Soc. Jpn.  74  Suppl. (2005) 191-195.

[88]N.Maeshima, K. Okunishi, K.Okamoto and T. Sakai: Frustration-induced inversion in the S=1/2 bond-alternating spin chain, Phys. Rev. Lett.  93(2004) 127203-1-4

[87]T. Sakai, K. Okamoto, K. Okunishi and M. Sato: Anomalous magnetization process in frustrated spin ladders, J. Phys.: Condens. Matter.  16 (2004) S785-S789.

[86]T. Sakai, K. Okamoto, K. Okunishi, K. Kindo, Y. Narumi, Y. Hosokoshi, K. kato, K. Inoue and T. Goto: Magnetization plateaus and cusp in S=1 spin ladder, Physica B  346-347 (2004) 34-37

[85]T. Sakai: Field-Induced Order in Anisotropic Haldane Spin Chain, Physica B  345 (2004) 128-131.

[84]T. Sakai: Field-Induced Spin Liquids and Orders in Quasi-1D Gapped Systems, J. Magn. Magn. Mat.  272-276 (2004) 865-866.

[83] T. Sakai:  Finite Temperature Simulation Based on Lanczos Algorithm for Low-Dimensional Quantum Systems, in Computer Simulation Studies in Condensed Matter Physics XVI, edited by D. P. Landau, S. P. Lewis, H. -B. Shuttler (Springer, Berlin, 2004) p. 47-60.

[82] T. Sakai: Investigation on charge stripe formation in an extended t-J model, J. Phys. A: Math. Gen.  36(2003) 9303-9310.

[81] T. Sakai, N. Okazaki, K. Okamoto, K. Kindo, Y. Narumi, Y. Hosokoshi, K. kato, K. Inoue and T. Goto: Magnetization plateaux in S=1 Organic Spin Ladder BIP-TENO, Physica B  329-333 (2003) 1203-1204.

[80] K. Okamoto and T. Sakai: Spin-Peierls mechanism for the non-trivial magnetization plateaux in two-leg spin ladders, Physica B  329-333 (2003) 1207-1208.

[79] T. Sakai, N. Okazaki, K. Okamoto, K. Kindo, Y. Narumi, Y. Hosokoshi, K. kato, K. Inoue and T. Goto: Magnetization plateaus in S=1 spin ladder, phys. stat. sol.  236(2003) 429-432.

[78] T. Sakai: Charge stripes and four-spin exchange interaction in high-Tc cuprates, Acta Physica Polonica B  34 (2003) 423-426.

[77] T. Sakai: Direct Observation of Spin Gaps in Electron Spin Resonance, J. Phys. Soc. Jpn.  72 (2003) Suppl. 53-60.

[76] T. Sakai and K. Okamoto: Quantum magnetization plateaux of an anisotropic ferrimagnetic chain, Phys. Rev. B  65 (2002) 214403-1-6.@

[75] S. Yamamoto, T. Sakai and A. Koga: Re-Entrant Quantum Phase Transitions in Antiferromagnetic Spin-1 Ladders, J. Phys. Soc. Jpn.  71 (2002) 1250-1253.

[74] T. Sakai and M. Takahashi: Spin flop in 1D quantum antiferromagnets, Prog. Theor. Phys. Suppl. No. 145 (2002) 125-129.

[73] O. Cepas, T. Sakai and T. Ziman: Dynamics, Selection Rules and Dzyaloshinski-Moriya Interaction in Strongly Frustrated Magnets,  Prog. Theor. Phys. Suppl. No. 145 (2002) 43-51.

[72] S. Yamamoto, T. Sakai and A. Koga: Quantum Phase Competition in Antiferromagnetic Spin-1 Ladders, Prog. Theor. Phys. Suppl. No. 145 (2002) 176-181.

[71] T. Sakai, K. Okamoto and N. Okazaki: Field-induced transitions and spin gaps in low-dimensional quantum antiferromagnets, in Quantum Properties of Low-Dimensional Antiferromagnets, edited by Y. Ajiro and J.-P. Boucher (Kyushu University Press, 2002) p. 62-69.

[70] T. Sakai: Charge Stripes Based on Higher-Order Interactions in Cuprate Superconductors, Physica C  378-381 (2002) 208-211.

[69] T. Sakai, N. Okazaki, T. Ohnishi and S. Takemura: ESR selection rules for direct transition of spin gap, in EPR in the 21th Century: Basic and Applications to Material, Life and Earth Sciences, edited by A. Kawamori, J. Yamauchi and H. Ohta (Elsevier, 2002) p.54-58

[68] K. Okamoto, N. Okazaki and T. Sakai: Mechanism for non-trivial magnetization plateaux of an S=1 frustrated spin ladder, J. Phys. Soc. Jpn.  71(2002) suppl. 196-198

[67] N. Okazaki, K. Okamoto and T. Sakai: Magnetization plateau in the S=1 spin ladder with competing interactions,  J. Phys. Chem. Solid  63(2002) 1455-1458.

[66] T. Sakai and Y. Takahashi: Numerical Study on Pseudogap Phenomena in High-Tc Cuprates, J. Phys. Chem. Solid  63 (2002) 1385-1388.

[65] T. Sakai: Electron spin resonance absorption from the ground state of gapped spin systems, phys. stat. sol. (a)  189 (2002) 1063-1068.

[64] A. Nakasu, K. Totsuka, Y. Hasegawa, K. Okamoto and T. Sakai:  Field-induced gap due to four-spin exchange in a spin ladder, J. Phys.: Condens. Matter  13 (2001) 7421-7428.

[63] T. Sakai: Stripes due to the next-nearest neighbor exchange in high-Tc cuprates, Phys. Rev. B  63 (2001) 140509(R).

[62] T. Nakanishi, S. Yamamoto and T. Sakai: Low-Temperature Properties of Quasi-One-Dimensional Molecule-Based Ferromagnets, J. Phys. Soc. Jpn. 70 (2001) 1380-1389.

[61] T. Sakai : Field-induced transition of the Haldane antiferromagnets, J. Appl. Phys.  89 (2001) 7195-7197.

[60] T. Sakai and S. Yamamoto : Quantum Magnetization Plateaux in Ferrimagnetic Spin Chains, J. Magn. Magn. Mat.  226-230 (2001) 645-646

[59] K. Okamoto, N. Okazaki and T. Sakai: Magnetization Plateau of an S=1 Spin Ladder, J. Phys. Soc. Jpn  70 (2001) 636-639.

[58] T. Sakai : Local Lattice Distortion in High-Tc Cuprates, J. Synchrotron Radiation,  8 (2001) 848-850.

[57] T. Sakai and D. Poilblanc : Dynamic Lattice Distortions in High-T_c Cuprates, in Physics in Local Lattice Distortions, eds. H. Oyanagi and A. Bianconi (Ammerican Institute of Physics, 2001) p.102-109

[56] T. Sakai, O. Cepas and T. Ziman : Selection Rule of ESR for Spin Gap Systems, Physica B  294-295 (2001) 26-29.

[55] M. Hagiwara, Y. Narumi, K. Kindo, N. Maeshima, K. Okunishi,T. Sakai and M. Takahashi : High Field Magnetization of an S=1/2 Zigzag Chain Conpound (N2H5)CuCl3, Physica B  294-295 (2001) 83-86.

[54] T. Sakai and Y. Takahashi : Pseudo Gap and Antiferromagnetic Spin Correltion in High-Tc Cuprates, J. Phys. Chem. Sol.  62 (2001) 203-206

[53] T. Sakai and Y. Takahashi : Pseudogap Induced by Antiferromagnetic Spin Correlation in High-Temperature Superconductors, J. Phys. Soc. Jpn  70 (2001) 272-277.

[52] T. Sakai : Mechanism of Stripes in t-J model, Int. J. Mod. Phys. B  29-31 (2000) 3662-3667.

[51] T. Sakai and S. Yamamoto : Coexistent quantum and classical aspects of magnetization plateaux in alternating spin chains, J. Phys.: Concens. Matter  12 (2000) 9787-9797.

[50] T. Sakai : Field-induced long-range order in the S=1 antiferromagnetic chain, Phys. Rev. B  62 (2000) R9240-9243.@

[49] T. Sakai, O. Cepas and T. Ziman : An Electron Spin Resonance Selection Rule for Spin-Gapped Systems, J. Phys. Soc. Jpn.  69 (2000) 3521-3524.

[48] S. Yamamoto, T. Fukui and T. Sakai : Characterization of ferrimagnetic Heisenberg chains according to the constituent spins, Eur. Phys. J. B  15 (2000) 211-219.

[47] T. Sakai and N. Okazaki : Magnetic properties of frustrated spin ladder, J. Appl. Phys.  87 (2000) 5893-5895.

[46] T. Sakai and S. Yamamoto : Magnetization plateau in one-dimensional quantum ferrimagnets, Prog. Theor. Phys. Suppl. No.138 (2000) 513-514.

[45] N. Okazaki, J. Miyoshi and T. Sakai : Magnetization plateau in the frustrated spin ladder, Physica B  281&282 (2000) 659-660.

[44] T. Sakai and Y. Takahashi : Pseudo-Gap Behavior of High-Tc Cuprates, Physica B  281&282 (2000) 800-801.

[43] T. Sakai, N. Okazaki and J. Miyoshi : Frustrated spin ladder in magnetic field, Physica B  284-288 (2000) 1603-1604.

[42] N. Okazaki, K. Okamoto and T. Sakai : Field-Induced Spin Gaps in the Frustrated Spin Ladder, J. Phys. Soc. Jpn.  69 (2000) 2419-2422.

[41] N. Okazaki, J. Miyoshi and T. Sakai : Magnetization plateau in the frustrated spin ladder, J. Phys. Soc. Jpn.  69(2000) 37-40.

[40] S. Yamamoto and T. Sakai : Multiplateau magnetization curves of one-dimensional Heisenberg ferrimagnets, Phys. Rev. B  62 (2000) 3795-3800.

[39] S. Yamamoto and T. Sakai : Breakdown of a Magnetization Plateau due to Anisotropy in Heisenberg Mixed-Spin Chains, J. Phys. Condens. Matter.  11 (1999) 5175-5186.

[38] T. Sakai and M. Takahashi : Metamagnetism of antiferromagnetic XXZ quantum spin chains, Phys. Rev. B  60 (1999) 7295-7298.

[37] T. Sakai : Spin flop in one-dimensional quantum antiferromagnets, Phys. Rev. B  60 (1999) 6238-6241.

[36] T. Sakai and S. Yamamoto : Critical Behavior of Anisotropic Heisenberg Mixed-Spin Chains in a Field, Phys. Rev. B  60 (1999) 4053-4056.

[35] T. Sakai and Y. Hasegawa : Magnetization plateau in the spin ladder with the four-spin exchange, Phys. Rev. B  60 (1999) 48-51.

[34] S. Yamamoto and T. Sakai : Low-Energy Structure of Heisenberg Ferrimagnetic Spin Chains, J. Phys. Soc. Jpn.  67 (1998) 3711-3714.

[33] T. Sakai and Y. Takahashi : Pseudo-Gap Behavior in Dynamical Properties of High-Tc Cuprates, J. Phys. Soc. Jpn.  67 (1998) 2630-2632.

[32] T. Sakai : Field induced transition of the S=1 antiferromagnetic chain with anisotropy, Phys. Rev. B  58 (1998) 6268-6272.@

[31] T. Sakai and M. Takahashi : Anisotroic S=3/2 Antiferromagnetic Chain in a Magnetic Field, Physica B  246-247 (1998) 375-377.

[30] Y. Takahashi and T. Sakai : Theory of itinerant electron metamagnetism. II, J. Phys. Condens. Matter  8 (1998) 5373-5382.

[29] T. Sakai and M. Takahashi : Critical exponent in the magnetization curve of quantum spin chains, Phys. Rev.  B 57 (1998) R8091-8094.

[28] T. Sakai and M. Takahashi : Magnetization Plateau in an S=3/2 Antiferromagnetic Heisenberg Chain with Anisotropy, Phys. Rev.  B 57 (1998) R3201-3204.

[27] T. Sakai, D. Poilblanc and D. J. Scalapino : Hole Pairing and Phonon Dynamics in Generalized 2D t-J-Holstein Models, Phys. Rev.  B 55 (1997) 8445-8451.

[26] D. Poilblanc, T. Sakai, D. J. Scalapino and W. Hanke : Multimode Electron-Phonon Coupling in the Two-Dimensional t-J-Holstein Model, Europhys. Lett.  34 (1996) 367-372.

[25] M. Takahashi and T. Sakai : Haldane Magnets and Related 1D Magnets ``Properties in Magnetic Field'', in Computational Physics as a New Frontier in Condensed Matter Research, eds. H. Takayama, M. Tsukada, H. Shiba, F. Yonezawa, M. Imada and Y. Okabe (The Physical Society of Japan, 1995) p. 180-186

[24] Y. Takahashi and T. Sakai : Theory of Itinerant Electron Metamagnetism, J. Phys. Condens. Matter  7 (1995) 6279-6290.

[23] M. Isoda, Y. Takahashi and T. Sakai : Antiferromagnetism in Half-Metallic f-electron system, J. Magn. Magn. Mat.  140-144(1995) 1385-1386

[22] Y. Takahashi and T. Sakai : Theory of Itinerant Electron Metamagnetism, J. Magn. Magn. Mat.  140-144 (1995) 193-194.

[21] H. Shiba, T. Sakai, B. Luethi, W. Palme and M. Sieling : ESR Absorption from the Ground State in Haldane Systems: Theory and Experiment, J. Magn. Magn. Mat.  140-144 (1995) 1590-1594.

[20] T. Sakai : Alternating Spin Chain in a Magnetic Field, J. Magn. Magn. Mat.  140-144 (1995) 1619-1620.

[19] T. Sakai : Phase Transition of S=1/2 Bond-Alternating Chain in a Magnetic Field, J. Phys. Soc. Jpn  64@(1995) 251-259

[18] T. Sakai and H. Shiba : Theory of ESR Absorption from the Ground State of NENP, Physica  B 201 (1994) 182-185

[17nM. Isoda, Y. Takahashi and T. Sakai : Magnetic Properties of Half-Metallic f-electron Systems, J. Phys. Soc. Jpn.  63 (1994) 1889-1899

[16] T. Sakai and H. Shiba : Numerical Study of a Model for NENP : One-Dimensional S=1 Antiferromagnet in a Staggered Field, J. Phys. Soc. Jpn.  63  (1994) 867-871.

[15] T. Sakai and M. Takahashi : Numerical Study of the String Order in S=1 Antiferromagnetic Heisenberg Chain, J. Phys. Soc. Jpn.  63 (1994) 755-761.

[14] T. Sakai : S=1 Antiferromagnetic Heisenberg Chain in a Magnetic Field, in Computer Aided Innovation of New Materials II, edited by M.Doyama et.al. (Elsevier, 1993) p.421-424.

[13] T. Sakai and M.Takahashi : Anisotropic S=1 Antiferromagnetic Heisenberg Chain in a Magnetic Field, J. Phys. Soc. Jpn.  62  (1993) 750-758.

[12]T. Sakai and M. Takahashi : Haldane Antiferromagnet in a Magnetic Field, in Computational Approaches is Condensed-Matter Physics, edited by S. Miyashita, M. Imada and H. Takayama (Springer, 1992) p171-172

[11]T. Sakai and M. Takahashi : Finite-Size Corrections and Spin Correlations of Magnetized S=1 Antiferromagnetic Heisenberg Chain, J. Phys. Soc. Jpn.  60 (1991) 3615-3619.

[10]T. Sakai and M. Takahashi : S=1 Antiferromagnetic Heisenberg Chain with an Axial-Symmetry-Breaking Anisotropy, Phys. Rev.  B 44  (Rapid Communications) (1991) 10385-10388.

[9]T. Sakai and M. Takahashi : S=1 Antiferromagnetic Heisenberg Chain in a Magnetic Field, Phys. Rev.  B 43 (1991) 13383-13393.

[8]M. Takahashi and T. Sakai : Magnetization Curve and Correlation Function of Haldane-Gap Antiferromagnet in Strong Magnetic Field, J. Phys. Soc. Jpn. 60 (1991) 760-763.

[7]K. Nomura and T. Sakai : Nonlinear Magnetization of the 1D S=1 Antiferromagnet, Phys. Rev.  B 44  (1991) 5092-5094.

[6]K. Nomura, T. Sakai and M. Takahashi : Ground-State Properties of 1D S=1 XXZ Model, J. Magn. Magn. Mat.  90 & 91 (1990) 223-224

[5]T. Sakai and M. Takahashi : Transverse Antiferromagnetism of Magnetized Haldane-Gap System, J. Phys. Soc. Jpn. 59 (1990) 4227-4230.

[4]T. Sakai and M. Takahashi : Effect of Haldane Gap on Quasi-One-Dimensional Systems, Phys. Rev. B 42 (1990) 4537-4543.

[3] T. Sakai and M. Takahashi : Finite-Size Scaling Study of S=1 XXZ Spin Chain, J. Phys. Soc. Jpn.  59  (1990) 2688-2693.

[2] T. Sakai and M. Takahashi : Energy Gap of the S=1 Antiferromagnetic Heisenberg Chain, Phys. Rev. B 42 (Rapid Communications) (1990) 1090-1092.

[1] T. Sakai and M. Takahashi : The Ground State of Quasi-One-Dimensional Heisenberg Antiferromagnets, J. Phys. Soc. Jpn. 58 (1989) 3131-3142.