古賀 昌久Akihisa Koga
☰

研究業績

Publications

会議録

    2026

    Dimensionality Effect on Exceptional Fermionic Superfluidity with Spin-Dependent Asymmetric Hopping S. Takamori, K. Yamamoto, A. Koga, J. Low Temp. Phys., 222, 37 (2026).

    2023

    Efficient Scheme for Time-dependent Thermal Pure Quantum State: Application to the Kitaev Model with Armchair Edges H. Taguchi, A. Koga, and Y. Murakami, SciPost Phys. Proc., 11, 003.1-003.7 (2023).
    High-harmonic generation in the Rice-Mele model: Role of intraband current originating from interband transition K. Nagai, Y. Murakami, and A. Koga, JPS Conf. Proc., 38, 011172 1-6 (2023).
    Field-direction Dependence of Majorana-mediated Spin Transport H. Taguchi, A. Koga, Y. Murakami, J. Nasu, and H. Tsuchiura, JPS Conf. Proc., 38, 011152 1-6 (2023).
    Confined states in the tight-binding model on the hexagonal golden-mean tiling T. Matsubara, A. Koga, and S. Coates, J. Phys.: Conf. Ser., 2461, 012003 1-8 (2023).

    2022

    Photoinduced Phase Transition in Two-Band model on Penrose Tiling K. Inayoshi, Y. Murakami, and A. Koga, J. Phys.: Conf. Ser., 2164, 012050 1-4 (2022).
    Majorana excitations in the anisotropic Kitaev model with an ordered-flux structure A. Hashimoto, Y. Murakami, and A. Koga, J. Phys.: Conf. Ser., 2164, 012028 1-4 (2022).

    2021

    Ferromagnetically ordered metal in the single-band Hubbard model A. Koga, Y. Kamogawa, and J. Nasu, AIP Conf. Proc., 2319, 130001 1-4 (2021).

    2020

    Magnetic properties of the S = 1 Kitaev model with anisotropic interactions T. Minakawa, J. Nasu, and A. Koga, JPS Conf. Proc., 30, 011086 1-6 (2020).

    2019

    Magnetic properties in the metallic magnets with large anisotropy Y. Taguchi, J. Nasu, A. Koga, T. Yoshioka, and H. Tsuchiura, J. Low Temp. Phys., 196, 321-326 (2019).
    Quasiperiodicity and valence fluctuation in the spin-1/2 Falicov-Kimball model J. Nasu, R. Shinzaki, and A. Koga, J. Low Temp. Phys., 196, 155-162 (2019).
    Ground-state properties for bilayer Kitaev model: dimer expansion study A. Koga, H. Tomishige, and J. Nasu, J. Supercond. Nov. Magn., 32, 1827-1830 (2019).

    2018

    Ground-state phase diagram in the Kugel-Khomskii model with finite spin-orbit interactions A. Koga, S. Nakauchi, and J. Nasu, Physica B, 536, 369-371 (2018).

    2017

    Cluster Size Effects on Electronic Reconstruction in Quasiperiodic System R. Shinzaki, J. Nasu, and A. Koga, J. Phys.: Conf. Ser., 809, 012022 1-4 (2017).

    2016

    DMFT Study for Valence Fluctuations in the Extended Periodic Anderson Model R. Shinzaki, J. Nasu, and A. Koga, J. Phys.: Conf. Ser., 683, 012041 1-6 (2016).
    Intersite electron correlations in a Hubbard model on inhomogeneous lattices N. Takemori, A. Koga, and H. Hafermann, J. Phys.: Conf. Ser., 683, 012040 1-6 (2016).

    2015

    DMFT study of the local correlation effects in quasi-periodic system N. Takemori and A. Koga, J. Phys.: Conf. Ser., 592, 012038 1-6 (2015).
    Diagrammatic Quantum Monte Carlo Study of Nonequilibrium Transport through a Quantum Dot coupled to Normal and Superconducting Leads A. Koga, JPS Conf. Proc., 4, 011003 1-4 (2015).
    Stabilities of Superfluid and Density Wave States in Fermionic Mass Imbalanced Optical Lattices N. Takemori and A. Koga, JPS Conf. Proc., 4, 011006 1-4 (2015).

    2014

    Cluster mean-field approach with density matrix renormalization group: Application to the hard-core bosonic Hubbard model on a triangular lattice R. Suzuki and A. Koga, JPS Conf. Proc., 3, 016005 1-6 (2014).
    Nonequilibrium transport through a quantum dot coupled to normal and superconducting leads A. Koga, JPS Conf. Proc., 3, 012018 1-6 (2014).
    Valence Fluctuations in the Extended Periodic Anderson Model at Finite Temperatures Y. Kojima and A. Koga, JPS Conf. Proc., 1, 012106 1-4 (2014).

    2013

    Metal-Insulator transition in optical lattice system with site-dependent interactions T. Saitou, A. Koga and A. Yamamoto, J. Supercond. Nov. Magn., 26, 1771-1774 (2013).

    2012

    Dynamical properties of ultracold fermions with attractive interactions in an optical lattice A. Koga and P. Werner, J. Phys.: Conf. Ser., 391, 012144 1-4 (2012).

    2011

    Superfluid state in the periodic Anderson model with attractive interactions A. Koga and P. Werner, J. Phys.: Conf. Ser., 302, 012040 1-6 (2011).
    Superfluid gap formation in a fermionic optical lattice with spin imbalanced populations A. Koga and P. Werner, J. Phys.: Conf. Ser., 273, 012116 1-4 (2011).
    Pseudogap behavior in the infinite dimensional attractive Hubbard model A. Koga and P. Werner, Mod. Phys. Lett. B, 25, 973-978 (2011).
    Polarized superfluid state in a three-dimensional fermionic optical lattice A. Koga, J. Bauer, P. Werner, Th. Pruschke, Physica E, 43, 697-701 (2011).

    2010

    Analysis of superfluid state of ultracold fermions with attractive interactions in two-dimensional optical lattices Y. Fujihara, A. Koga, and N. Kawakami, Physica C, 470, S991-S992 (2010).
    Magnetic transition in the Hubbard model on the triangular lattice T. Yoshioka, A. Koga, and N. Kawakami, Physica B, 405, S179-S181 (2010).
    Mott transition in the Hubbard model on the triangular lattice T. Yoshioka, A. Koga, and N. Kawakami, Phys. Status Solidi B, 247, 635-637 (2010).
    Magnetically Ordered State of Cold Fermions on a Decorated Square Lattice K. Noda, A. Koga, N. Kawakami and Th. Pruschke, J. Low Temp. Phys., 158, 79-84 (2010).

    2009

    Superfluidity and magnetism in two-dimensional fermionic optical lattice systems Y. Fujihara, A. Koga, and N. Kawakami, Physica B, 404, 3324-3327 (2009).
    Magnetic and Orbital Properties of the two-band Hubbard Model with Different Bandwidths Y. Koyama, A. Koga, N. Kawakami, and P. Werner, Physica B, 404, 3267-3270 (2009).
    Supersolid state in a fermionic optical lattice system A. Koga, T. Higashiyama, K. Inaba, S. Suga and N. Kawakami, J. Phys.: Conf. Ser., 150, 032046 1-4 (2009).
    Mott insulating state in a quarter-filled two-orbital Hubbard chain with different bandwidths S. Miyashita, Y. Yamashita, K. Yonemitsu, A. Koga, and N. Kawakami, J. Phys.: Conf. Ser., 150, 042128 1-4 (2009).
    Zero-temperature Phase Diagram of Two Dimensional Hubbard Model K. Inaba, A. Koga, S. Suga, and N. Kawakami, J. Phys.: Conf. Ser., 150, 042066 1-4 (2009).

    2008

    Variational Monte Carlo analysis of singlet-pairing state in a system with inhomogeneous potential Y. Fujihara, A. Koga, and N. Kawakami, J. phys. Chem. Solid, 69, 3388-3391 (2008).
    Instability of plaquette valence-bond crystal phase in planar pyrochlore electron system T. Yoshioka, A. Koga, and N. Kawakami, Physica B, 403, 1248-1250 (2008).
    Phase transitions in the extended periodic Anderson model A. Koga, N. Kawakami, R. Peters, and Th. Pruschke, Physica B, 403, 1378-1380 (2008).

    2007

    Electron correlations in the Hubbard model on the planar pyrochlore lattice A. Koga, T. Yoshioka, N. Kawakami, H. Yokoyama, Physica C, 460-462, 1070-1071 (2007).
    Mott transition of correlated electrons on the Kagome lattice S. Kuratani, A. Koga, N. Kawakami, J. Phys. Condens. Matter, 19, 145252 1-5 (2007).
    Superconductivity in non-centrosymmetric materials M. Sigrist, D. F. Agterberg, P. A. Frigeri, N. Hayashi, R. P. Kaur, A. Koga, I. Milat, K. Wakabayashi, Y. Yanase, J. Mag. Mag. Mat., 310, 536-540 (2007).
    Quantum Phase Transitions in the Hubbard Model on the Planar Pyrochlore Lattice A. Koga, T. Yoshioka, N. Kawakami, H. Yokoyama, J. Mag. Mag. Mat., 310, 867-869 (2007).
    Systematic Analysis of the Hubbard Model on the Checkerboard Lattice T. Yoshioka, A. Koga, and N. Kawakami, J. Mag. Mag. Mat., 310, 873-875 (2007).
    Variational Monte Carlo Study of Hubbard Model with Harmonic Confinement Y. Fujihara, A. Koga, and N. Kawakami, J. Mag. Mag. Mat., 310, 882-884 (2007).
    Thermodynamic properties of the two-orbital Hubbard Model K. Inaba, A. Koga, S. Suga, and N. Kawakami, J. Mag. Mag. Mat., 310, 876-878 (2007).
    Quantum Monte Carlo Study of Impurity Anderson Models with Degenerate Orbitals Y. Koyama, A. Koga, and N. Kawakami, J. Mag. Mag. Mat., 310, 405-407 (2007).

    2006

    Variational Monte Carlo Study of Two Dimensional Multi-Orbital Hubbard Model A. Koga, N. Kawakami, H. Yokoyama, and K. Kobayashi, AIP Conf. Proc., 850, 1458-1459 (2006).
    Magnetic fields and superconductivity without inversion symmetry in $\rm\bf CePt_3Si$ D. F. Agterberg, P. A. Frigeri, R. P. Kaur, A. Koga and M. Sigrist, Physica B, 378-380, 351-354 (2006).
    Analysis of checkerboard electron system by path-integral renormalization group method T. Yoshioka, A. Koga, and N. Kawakami, Physica B, 378-380, 294-296 (2006).

    2005

    Mott transitions in two-orbital Hubbard systems A. Koga, K. Inaba, and N. Kawakami, Prog. Theor. Phys. Suppl., 160, 253-273 (2005).
    Mott transitions in the multi-orbtial systems A. Koga, N. Kawakami, T.M. Rice, and M. Sigrist, Physica B, 359-361, 1366-1368 (2005).
    Field-induced phase transition in the periodic Anderson model T. Ohashi, A. Koga, S. Suga, and N. Kawakami, Physica B, 359-361, 738-740 (2005).
    Superconductivity without inversion symmetry in $\rm\bf CePt_3Si$ P. Frigeri, D. F. Agterberg, A. Koga, M. Sigrist, Physica B, 359-361, 371-373 (2005).

    2003

    Effect of degenerate orbitals on the Anderson lattice model A. Koga and N. Kawakami, J. Phys. Condens. Matter, 15, S2215-S2218 (2003).
    Quantum phase transitions in a frustrated orthogonal-dimer S=1 spin system A. Koga and N. Kawakami, Physica B, 329-333, 1267-1268 (2003).

    2002

    Magnetization curves of quasi-one-dimensional haldane systems A. Kawaguchi, A. Koga, N. Kawakami and K. Okunishi, Int. J. Mod. Phys. B, 16, 3339-3342 (2002).
    Hole-doping effects on an S=1 ladder system A. Koga, N. Kawakami and M. Sigrist, Physica B, 312-313, 606-608 (2002).
    Hole-doping effects on orthogonal-dimer spin chain A. Kawaguchi, A. Koga, K. Okunishi and N. Kawakami, J. phys. Chem. Solid, 63, 1431-1434 (2002).
    First-Order Phase Transitions in Frustrated Spin Systems A. Koga, A. Kawaguchi, K. Okunishi and N. Kawkami, Prog. Theor. Phys. Suppl., 145, 52-57 (2002).
    Quantum phase competition in antiferromagnetic spin-1 ladders S. Yamamoto, T. Sakai, and A. Koga, Prog. Theor. Phys. Suppl., 145, 176-181 (2002).

    2001

    Quantum phase transitions for the three-dimensional orthogonal-dimer spin system A. Koga and N. Kawakami, Comp. Phys. Comm., 142, 172-175 (2001).