論文リスト
  • X-ray Magnetic Circular Dichroism Arising from the Magnetic Dipole Moment in Antiferromagnets
    Kensuke Kurita, Takashi Koretsune
    J. Phys. Soc. Jpn. 93 024705 (2024)
  • Interface tool from Wannier90 to RESPACK: wan2respack
    Kensuke Kurita, Takahiro Misawa, Kazuyoshi Yoshimi, Kota Ido, Takashi Koretsune
    Comp. Phys. Comm. 292 108854 (2023)
  • Nodal-line resonance generating the giant anomalous Hall effect of Co3Sn2S2
    F. Schilberth, M.-C. Jiang, S. Minami, M. A. Kassem, F. Mayr, T. Koretsune, Y. Tabata, T. Waki, H. Nakamura, G.-Y. Guo, R. Arita, I. Kézsmárki, and S. Bordács
    Phys. Rev. B 107 214441 (2023)
  • Importance of self-consistency in first-principles Eliashberg calculation for superconducting transition temperature
    Tianchun Wang, Takuya Nomoto, Takashi Koretsune, Ryotaro Arita
    J. Phys. Chem. Solids 178 111348 (2023)
  • Ultrafast Dynamics of Intrinsic Anomalous Hall Effect in the Topological Antiferromagnet Mn3Sn
    Takuya Matsuda, Tomoya Higo, Takashi Koretsune, Natsuki Kanda, Yoshua Hirai, Hanyi Peng, Takumi Matsuo, Naotaka Yoshikawa, Ryo Shimano, Satoru Nakatsuji, and Ryusuke Matsunaga
    Phys. Rev. Lett. 130 126302 (2023)
  • Construction of maximally-localized Wannier functions using crystal symmetry
    Takashi Koretsune
    Comp. Phys. Comm. 285 108645 (2023)
  • sparse-ir: Optimal compression and sparse sampling of many-body propagators
    Markus Wallerberger, Samuel Badr, Shintaro Hoshino, Sebastian Huber, Fumiya Kakizawa, Takashi Koretsune, Yuki Nagai, Kosuke Nogaki, Takuya Nomoto, Hitoshi Mori, Junya Otsuki, Soshun Ozaki, Thomas Plaikner, Rihito Sakurai, Constanze Vogel, Niklas Witt, Kazuyoshi Yoshimi, Hiroshi Shinaoka
    Software X 21 101266 (2023)
  • Topological Nernst effect emerging from real-space gauge field and thermal fluctuations in a magnetic skyrmion lattice
    H. Oike, T. Ebino, T. Koretsune, A. Kikkawa, M. Hirschberger, Y. Taguchi, Y. Tokura, and F. Kagawa
    Phys. Rev. B 106 214425 (2022)
  • Optimal alloying in hydrides: Reaching room-temperature superconductivity in LaH10
    Tianchun Wang, José A. Flores-Livas, Takuya Nomoto, Yanming Ma, Takashi Koretsune, and Ryotaro Arita
    Phys. Rev. B 105 174516 (2022)
  • Wannier-based implementation of the coherent potential approximation with applications to Fe-based transition metal alloys
    Naohiro Ito, Takuya Nomoto, Koji Kobayashi, Sergiy Mankovsky, Kentaro Nomura, Ryotaro Arita, Hubert Ebert, and T. Koretsune
    Phys. Rev. B 105 125136 (2022)
  • Large anomalous Nernst effect and nodal plane in an iron-based kagome ferromagnet
    T. Chen, S. Minami, A. Sakai, Y. Wang, Z. Feng, T. Nomoto, M. Hirayama, R. Ishi, T. Koretsune, R. Arita, and S. Nakatsuji
    Science Advances 8 (2022)
    Press release
  • Magneto-optical spectroscopy on Weyl nodes for anomalous and topological Hall effects in chiral MnGe
    Y. Hayashi, Y. Okamura, N. Kanazawa, T. Yu, T. Koretsune, R. Arita, A. Tsukazaki, M. Ichikawa, M. Kawasaki, Y. Tokura and Y. Takahashi
    Nature Communications 12 5974 (2021)
    Press release
  • X-ray study of ferroic octupole order producing anomalous Hall effect
    Motoi Kimata, Norimasa Sasabe, Kensuke Kurita, Yuichi Yamasaki, Chihiro Tabata, Yuichi Yokoyama, Yoshinori Kotani, Muhammad Ikhlas, Takahiro Tomita, Kenta Amemiya, Hiroyuki Nojiri, Satoru Nakatsuji, Takashi Koretsune, Hironori Nakao, Taka-hisa Arima, and Tetsuya Nakamura
    Nature Communications 12 5582 (2021)
    Press release
  • Absence of conventional room-temperature superconductivity at high pressure in carbon-doped H3S
    Tianchun Wang, Motoaki Hirayama, Takuya Nomoto, Takashi Koretsune, Ryotaro Arita, and José A. Flores-Livas
    Phys. Rev. B 104 064510 (2021)
  • Effect of symmetry breaking on short-wavelength acoustic phonons in the chiral magnet MnSi
    Y. Nii, Y. Hirokane, T. Koretsune, D. Ishikawa, A. Q. R. Baron, and Y. Onose
    Phys. Rev. B 104 L081101 (2021)
  • Quantum anomalous Hall effect in a three-dimensional topological-insulator–thin-film-ferromagnetic-metal heterostructure
    Katsuhiro Arimoto, Takashi Koretsune, Kentaro Nomura
    Phys. Rev. B 103 235315 (2021)
  • Anomalous transport due to Weyl fermions in the chiral antiferromagnets Mn3X, X = Sn, Ge
    Taishi Chen, Takahiro Tomita, Susumu Minami, Mingxuan Fu, Takashi Koretsune, Motoharu Kitatani, Ikhlas Muhammad, Daisuke Nishio-Hamane, Rieko Ishii, Fumiyuki Ishii, Ryotaro Arita and Satoru Nakatsuji
    Nature Comm. 12 572 (2021)
    Press release
  • Geometrical Hall effect and momentum-space Berry curvature from spin-reversed band pairs
    Max Hirschberger, Yusuke Nomura, Hiroyuki Mitamura, Atsushi Miyake, Takashi Koretsune, Yoshio Kaneko, Leonie Spitz, Yasujiro Taguchi, Akira Matsuo, Koichi Kindo, Ryotaro Arita, Masashi Tokunaga, and Yoshinori Tokura
    Phys. Rev. B 103 L041111 (2021)
  • Enhancement of the transverse thermoelectric conductivity originating from stationary points in nodal lines
    Susumu Minami, Fumiyuki Ishii, Motoaki Hirayama, Takuya Nomoto, T. Koretsune, and Ryotaro Arita
    Phys. Rev. B 102 205128 (2020)
  • Efficient ab initio Migdal-Eliashberg calculation considering the retardation effect in phonon-mediated superconductors
    Tianchun Wang, Takuya Nomoto, Yusuke Nomura, Hiroshi Shinaoka, Junya Otsuki, T. Koretsune, and Ryotaro Arita
    Phys. Rev. B 102 134503 (2020)
  • Giant magneto-optical responses in magnetic Weyl semimetal Co3Sn2S2
    Y. Okamura, S. Minami, Y. Kato, Y. Fujishiro, Y. Kaneko, J. Ikeda, J. Muramoto, R. Kaneko, K. Ueda, V. Kocsis, N. Kanazawa, Y. Taguchi, T. Koretsune, K. Fujiwara, A. Tsukazaki, R. Arita, Y. Tokura, and Y. Takahashi
    Nature Communications 11 4619 (2020)
  • Topological Kagome magnet Co3Sn2S2 thin flakes with high electron mobility and large anomalous Hall effect
    Miuko Tanaka, Yukako Fujishiro, Masataka Mogi, Yoshio Kaneko, Takamoto Yokosawa, Naoya Kanazawa, Susumu Minami, Takashi Koretsune, Ryotaro Arita, Seigo Tarucha, Michihisa Yamamoto, and Yoshinori Tokura
    Nano Lett. 20 7476 (2020)
  • Formation mechanism of helical Q structure in Gd-based skyrmion materials
    Takuya Nomoto, Takashi Koretsune, and Ryotaro Arita
    Phys. Rev. Lett. 125 117204 (2020)
  • Local force method for the ab initio tight-binding model: Effect of spin-dependent hopping on exchange interactions
    Takuya Nomoto, Takashi Koretsune, and Ryotaro Arita
    Phys. Rev. B 102 014444 (2020)
  • Systematic first-principles study of the on-site spin-orbit coupling in crystals
    Kensuke Kurita, Takashi Koretsune
    Phys. Rev. B 102 045109 (2020)
  • Iron-based binary ferromagnets for transverse thermoelectric conversion
    Akito Sakai, Susumu Minami, Takashi Koretsune, Taishi Chen, Tomoya Higo, Yangming Wang, Takuya Nomoto, Motoaki Hirayama, Shinji Miwa, Daisuke Nishio-Hamane, Fumiyuki Ishii, Ryotaro Arita and Satoru Nakatsuji
    Nature 581 53-57 (2020)
    Press release
  • Quantum crystal structure in the 250-kelvin superconducting lanthanum hydride
    Ion Errea, Francesco Belli, Lorenzo Monacelli, Antonio Sanna, Takashi Koretsune, Terumasa Tadano, Raffaello Bianco, Matteo Calandra, Ryotaro Arita, Francesco Mauri and Jose A. Flores-Livas
    Nature 578 66-69 (2020)
    Press release
    電波新聞記事(2020/2/14)や 科学新聞(2020/2/21)で取り上げられました。
    日経サイエンス2020年8月号に紹介記事が掲載されました。
  • Wannier90 as a community code: new features and applications
    Giovanni Pizzi, Valerio Vitale, Ryotaro Arita, Stefan Bluegel, Frank Freimuth, Guillaume Géranton, Marco Gibertini, Dominik Gresch, Charles Johnson, Takashi Koretsune, Julen Ibanez, Hyungjun Lee, Jae-Mo Lihm, Daniel Marchand, Antimo Marrazzo, Yuriy Mokrousov, Jamal Ibrahim Mustafa, Yoshiro Nohara, Yusuke Nomura, Lorenzo Paulatto, Samuel Ponce, Thomas Ponweiser, Junfeng Qiao, Florian Thöle, Stepan S. Tsirkin, Malgorzata Wierzbowska, Nicola Marzari, David Vanderbilt, Ivo Souza, Arash A Mostofi and Jonathan R Yates
    Journal of Physics: Condensed Matter 32 165902 (2020)
  • Microscopic characterization of the superconducting gap function in Sn1-xInxTe
    T. Nomoto, M. Kawamura, T. Koretsune, R. Arita, T. Machida, T. Hanaguri, M. Kriener, Y. Taguchi, and Y. Tokura
    Phys. Rev. B 101 014505 (2020)
  • Ferromagnetic state above room temperature in a proximitized topological Dirac semimetal
    Masaki Uchida, Takashi Koretsune, Shin Sato, Markus Kriener, Yusuke Nakazawa, Shinichi Nishihaya, Yasujiro Taguchi, Ryotaro Arita, and Masashi Kawasaki
    Phys. Rev. B 100 245148 (2019)
  • Realization of interlayer ferromagnetic interaction in MnSb2Te4 toward the magnetic Weyl semimetal state
    Taito Murakami, Yusuke Nambu, Takashi Koretsune, Gu Xiangyu, Takafumi Yamamoto, Craig M. Brown, and Hiroshi Kageyama
    Phys. Rev. B 100 195103 (2019)
  • Topological transitions among skyrmion- and hedgehog-lattice states in cubic chiral magnets
    Y. Fujishiro, N. Kanazawa, T. Nakajima, X. Z. Yu, K. Ohishi, Y. Kawamura, K. Kakurai, T. Arima, H. Mitamura, A. Miyake, K. Akiba, M. Tokunaga, A. Matsuo, K. Kindo, T. Koretsune, R. Arita and Y. Tokura
    Nature Communications 10 1059 (2019)
    Press release
  • Finite phenine nanotubes with periodic vacancy defects
    Zhe Sun, Koki Ikemoto, Toshiya M. Fukunaga, Takashi Koretsune, Ryotaro Arita, Sota Sato, Hiroyuki Isobe
    Science 363 151 (2019)
    Press release
  • Negative-pressure-induced helimagnetism in ferromagnetic cubic perovskites Sr1-xBaxCoO3
    H. Sakai, S. Yokoyama, A. Kuwabara, J. S. White, E. Canevet, H. M. Ronnow, T. Koretsune, R. Arita, A. Miyake, M. Tokunaga, Y. Tokura, and S. Ishiwata
    Phys. Rev. Materials 2 104412 (2018)
    Press release
  • Controlling the helicity of magnetic skyrmions in a beta-Mn-type high-temperature chiral magnet
    K. Karube, K. Shibata, J. S. White, T. Koretsune, X. Z. Yu, Y. Tokunaga, H. M. Rønnow, R. Arita, T. Arima, Y. Tokura, and Y. Taguchi
    Phys. Rev. B 98 155120 (2018)
  • Maximally Localized Wannier Orbitals and the Extended Hubbard Model for Twisted Bilayer Graphene
    Mikito Koshino, Noah F. Q. Yuan, Takashi Koretsune, Masayuki Ochi, Kazuhiko Kuroki, and Liang Fu
    Phys. Rev. X 8 031087 (2018)
  • Superconductivity in Anti-ThCr2Si2-type Er2O2Bi Induced by Incorporation of Excess Oxygen with CaO Oxidant
    K. Terakado, R. Sei, H. Kawasoko, T. Koretsune, D. Oka, T. Hasegawa, and T. Fukumura
    Inorganic Chemistry 57 10587 (2018)
  • Giant anomalous Nernst effect and quantum-critical scaling in a ferromagnetic semimetal
    Akito Sakai, Yo Pierre Mizuta, Agustinus Agung Nugroho, Rombang Sihombing, Takashi Koretsune, Michi-To Suzuki, Nayuta Takemori, Rieko Ishii, Daisuke Nishio-Hamane, Ryotaro Arita, Pallab Goswami and Satoru Nakatsuji
    Nature Physics 14 1119 (2018)
    Press release
  • Electronic Structure Calculation and Superconductivity in λ-(BETS)2GaCl4
    Hirohito Aizawa, Takashi Koretsune, Kazuhiko Kuroki, and Hitoshi Seo
    J. Phys. Soc. Jpn. 87 093701 (2018)
  • Anisotropic band splitting in monolayer NbSe2: implications for superconductivity and charge density wave
    Yuki Nakata, Katsuaki Sugawara, Satoru Ichinokura, Yoshinori Okada, Taro Hitosugi, Takashi Koretsune, Keiji Ueno, Shuji Hasegawa, Takashi Takahashi and Takafumi Sato
    npj 2D Materials and Applications 2 12 (2018)
  • Tailoring band structure and band filling in a simple cubic (IV, III)-VI superconductor
    M. Kriener, M. Kamitani, T. Koretsune, R. Arita, Y. Taguchi, and Y. Tokura
    Phys. Rev. Materials 2 044802 (2018)
  • Charge-transfer complexes based on C2v-symmetric benzo[ghi]perylene: comparison of their dynamic and electronic properties with those of D6h-symmetric coronene
    Yukihiro Yoshida, Shunsuke Tango, Kazuhide Isomura, Yuto Nakamura, Hideo Kishida, Takashi Koretsune, Masafumi Sakata, Yoshiaki Nakano, Hideki Yamochiag and Gunzi Saito
    Materials Chemistry Frontiers 2 1165 (2018)
  • Large magneto-thermopower in MnGe with topological spin texture
    Y. Fujishiro, N. Kanazawa, T. Shimojima, A. Nakamura, K. Ishizaka, T. Koretsune, R. Arita, A. Miyake, H. Mitamura, K. Akiba, M. Tokunaga, J. Shiogai, S. Kimura, S. Awaji, A. Tsukazaki, A. Kikkawa, Y. Taguchi and Y. Tokura
    Nature Communications 9 408 (2018)
    Press release
  • Large magneto-optical Kerr effect and imaging of magnetic octupole domains in an antiferromagnetic metal
    Tomoya Higo, Huiyuan Man, Daniel B. Gopman, Liang Wu, Takashi Koretsune, Olaf M. J. van't Erve, Yury P. Kabanov, Dylan Rees, Yufan Li, Michi-To Suzuki, Shreyas Patankar, Muhammad Ikhlas, C. L. Chien, Ryotaro Arita, Robert D. Shull, Joseph Orenstein, and Satoru Nakatsuji
    Nature Photonics 12 73-78 (2018)
    Press release
  • First-Principles Evaluation of the Dzyaloshinskii-Moriya Interaction
    T. Koretsune, T. Kikuchi and R. Arita
    J. Phys. Soc. Jpn. 87 041011 (2018)
  • Evidence for magnetic Weyl fermions in a correlated metal
    K. Kuroda, T. Tomita, M.-T. Suzuki, C. Bareille, A. A. Nugroho, P. Goswami, M. Ochi, M. Ikhlas, M. Nakayama, S. Akebi, R. Noguchi, R. Ishii, N. Inami, K. Ono, H. Kumigashira, A. Varykhalov, T. Muro, T. Koretsune, R. Arita, S. Shin, Takeshi Kondo and S. Nakatsuji
    Nature Materials 16 1090-1095 (2017)
    Press release
  • Efficient method to calculate the electron-phonon coupling constant and superconducting transition temperature
    T. Koretsune and R. Arita
    Comp. Phys. Comm. 220C 239 (2017)
  • Large anomalous Nernst e ect at room temperature in a chiral antiferromagnet
    Muhammad Ikhlas, Takahiro Tomita, Takashi Koretsune, Michi-To Suzuki, Daisuke Nishio-Hamane, Ryotaro Arita, Yoshichika Otani and Satoru Nakatsuji
    Nature Physics 13 1085-1090 (2017)
    Press release
  • Pentagon-Embedded Cycloarylenes with Cylindrical Shapes
    Shunpei Hitosugi, Sota Sato, Taisuke Matsuno, Takashi Koretsune, Ryotaro Arita, Hiroyuki Isobe
    Angewandte Chemie 56 9106-9110 (2017)
  • Weak phonon-mediated pairing in BiS2 superconductor from first principles
    C. Morice, R. Akashi, T. Koretsune, S. S. Saxena and R. Arita
    Phys. Rev. B 95 180505(R) (2017)
  • π-electron S=1/2 quantum spin-liquid state in an ionic polyaromatic hydrocarbon
    Y. Takabayashi, M. Menelaou, H. Tamura, N. Takemori, T. Koretsune, A. Stefancic, G. Klupp, A. J. C. Buurma, Y. Nomura, R. Arita, D. Arcon, M. J. Rosseinsky and P. Kosmas
    Nature Chemistry 9 635-643 (2017)
  • Cluster multipole theory for anomalous Hall effect in antiferromagnets
    M.-T. Suzuki, T. Koretsune, M. Ochi, and R. Arita
    Phys. Rev. B 95 094406 (2017)
  • Efficient blue electroluminescence from a single-layer organic device composed solely of hydrocarbons
    T. Izumi, T. Yi, K. Ikemoto, A. Yoshii, T. Koretsune, R. Arita, H. Kita, H. Taka, S. Sato and H. Isobe
    Chem. Asian J 12 730-733 (2017)
  • Structural Modulation of Macrocyclic Materials for Charge Carrier Transport Layers in Organic Light-Emitting Devices
    A. Yoshii, K. Ikemoto, T. Izumi, H. Kita, H. Taka, T. Koretsune, R. Arita, S. Sato and H. Isobe
    ECS Journal of Solid State Science and Technology 6 M3065 (2017)
  • Nonempirical Calculation of Superconducting Transition Temperatures in Light-Element Superconductors
    R. Arita, T. Koretsune, S. Sakai, R. Akashi, Y. Nomura, W. Sano
    Advanced Materials (2017)
  • Cationic pi-Stacking Columns of Coronene Molecules with Fully Charged and Charge-Disproportionated States
    Y. Yoshida, K. Isomura, M. Maesato, T. Koretsune, Y. Nakano, H. Yamochi, M. Kishida, and G. Saito
    Cryst. Growth Des. 16 5994 (2016)
  • Gate-Tuned Thermoelectric Power in Black Phosphorus
    Y. Saito, T. Iizuka, T. Koretsune, R. Arita, S. Shimizu, and Y. Iwasa
    Nano Letter 16 4819 (2016)
  • Dzyaloshinskii-Moriya Interaction as a Consequence of a Doppler Shift due to Spin-Orbit-Induced Intrinsic Spin Current
    T. Kikuchi, T. Koretsune, R. Arita, and G. Tatara
    Phys. Rev. Lett 116 247201 (2016)
    Press release
  • Two-dimensional metallic NbS2: growth, optical identification and transport properties
    S. Zhao, T. Hotta, T. Koretsune, K. Watanabe, T. Taniguchi, K. Sugawara, T. Takahashi, H. Shinohara, R. Kitaura
    2D Materials 3 025027 (2016)
  • Effect of Van Hove singularities on high-Tc superconductivity in H3S
    W. Sano, T. Koretsune, T. Tadano, R. Akashi, and R. Arita
    Phys. Rev. B 93 094525 (2016)
  • Conducting pi Columns of Highly Symmetric Coronene, The Smallest Fragment of Graphene
    Y. Yoshida, K. Isomura, H. Kishida, Y. Kumagai, M. Mizuno, M. Sakata, T. Koretsune, Y. Nakano, H. Yamochi, M. Maesato, and G. Saito
    Chemistry A European Journal 22 6023 (2016)
  • Aromatic hydrocarbon macrocycles for highly efficient organic light-emitting devices with single-layer architectures
    Jing Yang Xue, Tomoo Izumi, Asami Yoshii, Koki Ikemoto,Takashi Koretsune, Ryosuke Akashi, Ryotaro Arita, Hideo Taka, Hiroshi Kita, Sota Sato and Hiroyuki Isobe
    Chemical Science 7 896-904 (2016)
  • In-plane electric polarization of bilayer graphene nanoribbons induced by an interlayer bias voltage
    R. Okugawa, J. Tanaka, T. Koretsune, S. Saito, and S. Murakami
    Phys. Rev. Lett. 115 156601 (2015)
  • Control of Dzyaloshinskii-Moriya interaction in Mn1-xFexGe: a first-principles study
    T. Koretsune, N. Nagaosa, and R. Arita
    Scientific Reports 5 13302 (2015)
  • Field-direction control of the type of charge carriers in nonsymmorphic IrO2
    M. Uchida, W. Sano, K. S. Takahashi, T. Koretsune, Y. Kozuka, R. Arita, Y. Tokura, and M. Kawasaki
    Phys. Rev. B 91 241119(R) (2015)
  • Spin-disordered quantum phases in a quasi-one-dimensional triangular lattice
    Yukihiro Yoshida, Hiroshi Ito, Mitsuhiko Maesato, Yasuhiro Shimizu, Hiromi Hayama, Takaaki Hiramatsu, Yuto Nakamura, Hideo Kishida, Takashi Koretsune, Chisa Hotta and Gunzi Saito
    Nature Physics 11 679 - 683 (2015)
  • Large surface relaxation in the organic semiconductor tetracene
    Hazuki Morisaki, Takashi Koretsune, Chisa Hotta, Jun Takeya, Tsuyoshi Kimura and Yusuke Wakabayashi
    Nature Communications 5 5400 (2014)
    Press release
  • Evaluating model parameters of the kappa- and beta'-type Mott insulating organic solids
    T. Koretsune and C. Hotta
    Phys. Rev. B 89 045102 (2014)
    We elucidate the model parameters for a series of organic crystals called κ- and β'-type salts by constructing the maximally localized Wannier orbitals which reproduce the bulk energy band of the first-principles methods based on the density functional theory (DFT). These materials host a dimer Mott insulator, localizing one hole per dimerized ET molecules due to strong on-dimer interaction, Ud. For all these materials, we evaluate the parameters of the two representative effective lattice models in units of molecule and on dimer, and clarify two issues. First, the conventional relationships between the two models called "dimer approximation" does not hold. Second, contrary to the previous semiempirical estimates, the degree of dimerization (which approximates Ud) does not depend much on materials, and that the overall ground state properties are controlled by the degree of anisotropy of the triangular lattice, denoted as |tc/ta| in units of dimers. We update the DFT estimates |tc/ta| of κ-ET2Cu2(CN)3, showing that it falls on a class of regular triangle with the strongest degree of frustration.
  • Isotope composition dependence of band gap energy in diamond
    H. Watanabe, T. Koretsune, S. Nakashima, S. Saito and S. Shikata
    Phys. Rev. B 88 (2013) 205420
    We present experimental results on the band-gap energies of homoepitaxial diamond films with isotopic compositions ranging from nearly pure carbon-12 (12C) to nearly pure carbon-13 (13C). Diamond crystals were grown by microwave plasma-assisted chemical vapor deposition, which controls the isotope composition and minimizes the density of impurities and defects. We find that the isotope substitution of 12C by 13C increases the band-gap energy in diamond by up to 15.4 meV at 79 K. The increase at room temperature is estimated from the temperature dependence of the band-gap renormalization due to electron-phonon interaction and is found to be even larger than that at low temperatures. These results unambiguously demonstrate the possibility of band-gap engineering of diamond via control of the isotopic composition.
  • Magneto-orbital effect without spin-orbit interactions in a noncentrosymmetric zeolite-templated carbon structure
    T. Koretsune, R. Arita and H. Aoki
    Phys. Rev. B 86 (2012) 125207
    A peculiar manifestation of orbital angular momentum is proposed for a zeolite-templated carbon system, C36H9. The structure, being a network of nanoflakes in the shape of a "pinwheel", lacks inversion symmetry. While the unit cell is large, the electronic structure obtained with a first-principles density functional theory and captured as an effective tight-binding model in terms of maximally-localized Wannier functions, exhibits an unusual feature that the valence band top comes from two chiral states having orbital magnetic momenta of 1. The noncentrosymmetric lattice structure then makes the band dispersion asymmetric, as reminiscent of, but totally different from, spin-orbit systems. The unusual feature is predicted to imply a current-induced orbital magnetism when holes are doped.
  • Energetics and electronic properties of twisted single-walled carbon nanotubes
    K. Kato, T. Koretsune and S. Saito
    Phys. Rev. B 85 (2012) 115448
    We perform a systematic first-principles study of energetics and electronic properties of chiral carbon nanotubes (CNTs) in the density-functional theory. It is found that chiral CNTs possess slightly twisted ground-state geometries. Moderate-diameter CNTs show twisting-dependent electronic properties well classified by their chiral indices, while the electronic structures of small-diameter CNTs possess sizable but individually different twisting dependences, leading to metal-semiconductor transitions in some CNTs. The CNT having the widest fundamental gap is predicted to be the twisted (4,3) CNT.
  • One-dimensional alkali-doped C60 chains encapsulated in BN nanotubes
    T. Koretsune, S. Saito and M. L. Cohen
    Phys. Rev. B 83 (2011) 193406
    We study the energetics, electronic structures, and electron-phonon couplings of a one-dimensional potassium-doped C60 chain encapsulated in a boron nitride nanotube using the framework of the density-functional theory. We demonstrate that the reaction of potassium doping is exothermic and the resulting material is one-dimensional metal where conducting electrons are only in the C60 chain. Interestingly, the Fermi-level density of states has a peculiar pressure dependence and can be larger than those in the three-dimensional alkali-doped fullerene compounds, indicating the possibility of various phase transitions. We also discuss the electron-phonon couplings and the possibility of superconductivity.
  • Electronic structure and stability of layered superlattice composed of graphene and boron nitride monolayer
    Y. Sakai, T. Koretsune and S. Saito
    Phys. Rev. B 83 (2011) 205434
    We study superlattices with alternate stacking of graphene and boron nitride monolayers. We propose several candidate stacking sequences of the superlattices, and optimize their geometries based on the energetics in the framework of the density functional theory. From the total energies of the superlattices with the candidate stacking sequences, we identify the most stable stacking sequence. The atomic configuration of the superlattice with the most stable stacking sequence is found to have the shortest B-C distance among all the optimized superlattice geometries, indicating a strong interaction between the carbon and boron atoms. We also study the electronic structure of the superlattices in detail. It is revealed that the most stable structure exhibits metallic electronic properties.
  • "Ab initio derivation of the low-energy model for alkali-cluster-loaded sodalites"
    K. Nakamura, T. Koretsune and R. Arita
    Phys. Rev. B 80 (2009) 174420 (cond-mat/0907.4593v1 )
    An effective low-energy model describing magnetic properties of alkali-cluster-loaded sodalites is derived by ab initio downfolding. We start with constructing an extended Hubbard model for maximally localized Wannier functions. Ab initio screened Coulomb and exchange interactions are calculated by constrained random-phase approximation. We find that the system resides in the strong-coupling regime and thus the Heisenberg model is derived as a low-energy model of the extended Hubbard model. We obtain antiferromagnetic couplings ~O(10 K), being consistent with the experimental temperature dependence of the spin susceptibility. Importance of considering the screening effect in the derivation of the extended Hubbard model is discussed.
  • "Thermodynamic properties of Heisenberg model on a triangular lattice with two exchange couplings: Application to two-dimensional solid 3He adsorbed on graphite"
    T. Koretsune, M. Udagawa and M. Ogata
    Phys. Rev. B 80 (2009) 075408
    グラファイト上に吸着された3Heの二層目の固体相におけるギャップレスのスピン液体的状態を理解するため、一層目の効果を取り入れた三角格子とカゴメ格子を結ぶ二つのJを持つS=1/2のハイゼンベルグ模型を考え、有限温度Lanczos法と高温展開法を用いて調べた。その結果、あるパラメータ領域では、このモデルが有効模型として、それぞれエネルギースケールの異なる三角格子ハイゼンベルグ模型とカゴメ格子ハイゼンベルグ模型の和として書けることが分かった。さらに、この有効模型を使うと、3He固体相の実験における比熱のダブルピークや低温でのlinear-Tの振舞い、さらには帯磁率の異常な上昇などの振舞いをよく再現することが分かった。
  • "A new crystalline phase of four-fold coordinated silicon and germanium"
    Y. Fujimoto, T. Koretsune, S. Saito, T. Miyake and A. Oshiyama
    New Journal of Physics 10 (2008) 083001
    完全に4配位のみからなるbody-centered tetragonal (BCT)構造のSiとGeに対して第一原理計算を行った。 局所密度近似(LDA)を用いて、構造最適化を行い、最適化構造に対してGW計算を行った。 その結果、適当な引張応力によってこの構造が安定化することが分かった。 さらに、BCT-Si は間接ギャップが0.5eV程度の半導体となり、BCT-Geに至っては、キャリア濃度が2x10^19 cm-3 程度の半金属となることが分かった。 CT-SiとBCT-Geの状態密度は特徴的な構造をもっており、ダイアモンド構造の場合とは容易に区別できる。 また、伝導体の電子や価電子体のホールの有効質量はダイアモンド構造の場合と比較して軽くなる。 バンドギャップが小さく(あるいはなくなってしまう)起源についても議論する。
  • "Superconductivity in Thin Films of Boron-Doped Carbon Nanotubes"
    N. Murata, J. Haruyama, J. Reppert, A.M. Rao, T. Koretsune, S. Saito, M. Matsudaira and Y. Yagi
    Phys. Rev. Lett. 101 027002 (2008).
  • "Electronic structure of boron-doped carbon nanotube"
    T. Koretsune and S. Saito
    Physical Review B 77 165417 (2008).
    ホウ素ドープしたカーボンナノチューブの電子状態を密度汎関数法を用いて調べ、全エネルギーやバンド構造、状態密度を計算した。 様々な半径のホウ素ドープナノチューブに対しての形成エネルギーから、一般に細いチューブの法が炭素をホウ素に置換しやすいことが分かった。 (10,0)チューブに対して異なった濃度でドープした場合を計算し、低ホウ素密度に外挿することによりアクセプターレベルの深さが0.2eV程度であることが分かった。 さらに、超伝導の可能性を議論する上で重要となるFermi準位上での状態密度の濃度依存性について議論した。
  • "Exact Diagonalization Study of Mott Transition in the Hubbard Model on an Anisotropic Triangular Lattice"
    T. Koretsune, Y. Motome and A. Furusaki
    J. Phys. Soc. Jpn. 76 074719-1-10 (2007).
    2次元異方的三角格子上のハバード模型のMott転移を調べた。 厳密対角化法を用いて18サイトまでの格子に対して、Drudeの重みや電荷ギャップ、二重占有数、スピン構造因子を求めた。 これらの物理量を境界条件に対して平均をとってやり、有限サイズ効果を緩和させてやることで、Drudeの重みや電荷ギャップからMott転移の兆候を得ることができた。 また、スピン相関関数から反強磁性相の決定も行った。 これらの情報から、基底状態の相図において金属相と反強磁性相の中間に非磁性絶縁体相があらわれる可能性を指摘した。 さらに、この状態について以前の理論結果と比較し、非自明な絶縁体相の可能性について議論した。
  • "Pairing correlation functions in the triangular t-J model: d-wave and f-wave superconductivity"
    T. Koretsune and M. Ogata
    Phys. Rev. B 72 134513-1-6 (2005).
    2次元三角格子t-J模型の同時刻超伝導相関関数を高温展開法を用いて調べた。 超伝導相関の相関長や有効ペア間相互作用をT=0.2t程度まで求め、どの対称性の相関が発達しているのか調べた。 t>0でホールをドープした場合、d波の相関が最も成長していることが分かった。 逆に、t<0では強磁性相関と反強磁性相関の競合から、d波の他にp波やf波のトリプレットの相関も発達していることが分かった。 ただし、競合領域では成長は限定的で発散的な振る舞いとまではいかない。 一方、n=0.4あたりでは、f波の相関が発散的な振る舞いを示すが、有効的な引力は小さいことが分かった。 NaxCoO2 yH2O との比較についても議論する。
  • "Development of superconducting correlation at low temperatures in the two-dimensional t-J model"
    T. Koretsune and M. Ogata
    J. Phys. Soc. Jpn. 74, 1390-1393 (2005).
    2次元正方格子t-J模型の同時刻超伝導相関関数を高温展開法を用いて調べた。 相関関数の和や空間依存性、相関長をT=0.2t程度の低温まで求めた。 一粒子の寄与との比較から、dx2-y2波の相関は引力的であり、電子密度 n が 0.5 < n < 0.9 の領域においては低温において急激に成長していることが分かった。 この成長の温度はおよそJ/2ぐらいでスケールしている。 これは、2次元Hubbard模型に対する数値的な結果がintermediateな相関の領域で超伝導に否定的な結果をだしているのとは対照的な結果である。
  • "Feromagnetism on the Frustrated Lattices"
    T. Koretsune and M. Ogata
    J. Phys. Soc. Jpn. 72, 2437-2440 (2003).
    2次元三角格子、カゴメ格子上のt-J模型を高温展開法を用いて調べた。 一様帯磁率や基底状態のエネルギーの評価から、相図上の広い領域に渡って強磁性的な振る舞いをする領域があることが分かった。 これは正方格子上のt-J模型には見られなかった性質である。 この強磁性的な領域は、長岡の強磁性と低電子密度における金森強磁性が連続的につながっていることを示唆している。 また、三角格子の低濃度領域では部分強磁性の領域が広がっている可能性があることが分かった。
  • "Resonating-Valence-Bond States and Ferromagnetic Correlations in the Doped Triangular Mott Insulator"
    T. Koretsune and M. Ogata
    Phys. Rev. Lett. 89, 116401-1-4 (2002).
    2次元三角格子t-J模型を高温展開法を用いて調べた。 その結果、エントロピーや帯磁率に対する解析の結果、tの符号が非常に重要な役割を果たすことが分かった。 t>0の場合、帯磁率のピークはドープ量を増やしていくと高温側にシフトすることから、ドーピングによってRVB状態が出現していることが示唆される。 一方、t<0の場合、ドープとともに帯磁率のピークが消失し(T→0に向けて発散的な振舞い)、比熱係数のγは大きな値をとるようになることが分かった。 これは、Jによるシングレットの形成と長岡の強磁性の競合を表していると考えられる。

Proceedings
  • "Electronic structures of hexagonal boron-nitride monolayer: strain-induced effects"
    Y. Fujimoto, T. Koretsune and S. Saito
    J. Ceramic Soc. Jpn. 122 (2014) 346
  • "Electronic structures of carbon-doped hexagonal boron nitride sheet: A density-functional study"
    Y. Fujimoto, T. Koretsune and S. Saito
    JPS Conf. Proc. 1 (2014) 012066
  • "Twisting Effects on Carbon Nanotubes: A First-Principles Study with Helical Symmetry Operations"
    K. Kato, T. Koretsune and S. Saito
    J. Phys: Conf. Ser. 302 (2011) 012007
  • "Electronic structures and three-dimensional effects of the boron-doped carbon nanotubes"
    T. Koretsune and S. Saito
    Sci. Technol. Adv. Mater. 9 (2008) 044203
    ホウ素ドープカーボンナノチューブに対して密度汎関数による第一原理計算を行った。 超伝導の可能性について議論するため、(10,0)チューブにおいてホウ素濃度を変化させてバンドや状態密度の計算した。 その結果、Fermi準位上での状態密度は、ホウ素濃度を下げるとともに大きくなるという、定性的に rigid band で理解できる結果が得られた。 さらに3次元性の効果を調べるため、(10,0)チューブのバンドルの計算やホウ素ドープ(10,0)チューブと(19,0)チューブからなるdouble wallのカーボンナノチューブの計算を行った。 バンドルの計算では、層間の相互作用が比較的大きく、一次元的なvan Hove singularityはかなりなめらかになってしまうことが分かった。 これは層間の距離の制御が重要な役割を果たすことを意味している。 また、double wallの計算からは、バンド構造がほぼそれぞれのチューブのバンドの重ね合わせでよく、さらに内側にドープされたホールが外側のチューブにも広がることが分かった。
  • "Effective mass divergence in the infinite-U Hubbard model"
    T. Koretsune and M. Ogata
    Physica B. 378-380 323-324 (2006).
    強相関極限でのMott転移の性質を明らかにするため、U無限大のハバード模型を高温展開法を用いて調べた。 自由エネルギーを温度の逆数と電子密度の関数として求めた。 低温での振る舞いをエントロピーが温度に比例すると仮定することで、非常に精度よく絶対零度まで外挿することができ、その結果比熱係数γはn=1に向けて発散することが分かった。 さらに、その発散の仕方を調べると、γは1-nの-1.7乗から-1.8乗程度で発散しており、その臨界指数は格子構造などにほとんどよらないことが分かった。
  • "Possible pairing symmetry in the two-dimensional t-J model on square and triangular lattices"
    T. Koretsune and M. Ogata
    Physica B. 359-361 545-547 (2005).
  • "Effect of a geometrical frustration in the doped Mott insulator"
    T. Koretsune and M. Ogata
    Physica C. 388-389, 88-89 (2003).
  • "The ground state energy and entropy of the two-dimensional t-J model"
    T. Koretsune and M. Ogata
    J. Phys. Chem. Solids 63, 1419-1422 (2002).
    2次元正方格子t-J模型のエントロピーに対して温度の逆数で14次までの高温展開を行った。 S(E)を用いた高温展開級数の解析の結果、基底状態のエネルギーまでかなりの精度で得られること、エントロピーに二つのエネルギースケールに対応するこぶが存在することなどが分かった。

解説記事、本など