著者

Oda Tatsuki Pasquarello Alfredo

出版者

American Physical Society

雑誌

Physical Review B - Condensed Matter and Materials Physics (ISSN:10980121)

巻号頁・発行日

vol.70, no.13, pp.134402-1-134402-19, 2004-10-01

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金沢大学大学院自然科学研究科計算科学

著者

Ihara Y. Noda K. Kawamoto A.

出版者

American Physical Society

雑誌

Physical Review B (ISSN:10980121)

巻号頁・発行日

vol.90, no.4, pp.41107, 2014-07-25

被引用文献数

6

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The local electronic state at every crystallographically independent molecular site was separately investigated in the organic superconductor alpha-(BEDT-TTF)(2)NH4Hg(SCN)(4) using site-selective C-13-NMR spectroscopy. The density of states (DOS) at three molecular sites shows independent temperature variation, which is caused by the long-range Coulomb interaction. Comparing the present results with those for a nonsuperconducting counterpart alpha-(BEDT-TTF)(2)RbHg(SCN)(4), we found that the uniform DOS at two of three independent molecular sites is crucial to induce superconductivity. Taking the site-dependent DOS as a parameter, we constructed a phase diagram for a superconductor with long-range Coulomb interaction, an alpha-type BEDT-TTF family, and summarized the competition between charge instability and superconductivity.

著者

Kiuchi Kenta Kyutoku Koutarou Sekiguchi Yuichiro Shibata Masaru Wada Tomohide

出版者

American Physical Society

雑誌

Physical Review D (ISSN:15507998)

巻号頁・発行日

vol.90, no.4, 2014-08-28

被引用文献数

166

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連星中性子星の合体とブラックホールの進化過程に新解釈 -スーパーコンピュータ「京」で磁場の増幅機構が明らかに-. 京都大学プレスリリース. 2014-09-01.We perform high-resolution magnetohydrodynamics simulations of binary neutron star mergers in numerical relativity on the Japanese supercomputer K. The neutron stars and merger remnants are covered by a grid spacing of 70 m, which yields the highest-resolution results among those derived so far. By an in-depth resolution study, we clarify several amplification mechanisms of magnetic fields during the binary neutron star merger for the first time. First, the Kelvin-Helmholtz instability developed in the shear layer at the onset of the merger significantly amplifies the magnetic fields. A hypermassive neutron star (HMNS) formed after the merger is then subject to the nonaxisymmetric magnetorotational instability, which amplifies the magnetic field in the HMNS. These two amplification mechanisms cannot be found with insufficient-resolution runs. We also show that the HMNS eventually collapses to a black hole surrounded by an accretion torus which is strongly magnetized at birth.

著者

Nagaya K. Motomura K. Kukk E. Fukuzawa H. Wada S. Tachibana T. Ito Y. Mondal S. Sakai T. Matsunami K. Koga R. Ohmura S. Takahashi Y. Kanno M. Rudenko A. Nicolas C. Liu X.-J. Zhang Y. Chen J. Anand M. Jiang Y. H. Kim D.-E. Tono K. Yabashi M. Kono H. Miron C. Yao M. Ueda K.

出版者

American Physical Society

雑誌

Physical Review X (ISSN:21603308)

巻号頁・発行日

vol.6, no.2, 2016-06-16

被引用文献数

17

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X線自由電子レーザーの超短パルスでリボ核酸塩基分子中の電荷と原子の動きを可視化-ヨウ化ウラシルによる放射線増感効果の機構解明. 京都大学プレスリリース. 2016-07-04.

著者

Takatsu H. Onoda S. Kittaka S. Kasahara A. Kono Y. Sakakibara T. Kato Y. Fåk B. Ollivier J. Lynn J. W. Taniguchi T. Wakita M. Kadowaki H.

出版者

American Physical Society

雑誌

Physical Review Letters (ISSN:00319007)

巻号頁・発行日

vol.116, no.21, 2016-05-26

被引用文献数

43

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スピン液体の近くの「隠れた秩序」. 京都大学プレスリリース. 2016-05-27.

著者

Dushenko S. Ago H. Kawahara K. Tsuda T. Kuwabata S. Takenobu T. Shinjo T. Ando Y. Shiraishi M.

出版者

American Physical Society

雑誌

Physical Review Letters (ISSN:10797114)

巻号頁・発行日

vol.116, no.16, 2016-04-21

被引用文献数

71

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次世代スピントロニクス材料であるグラフェンにおいてスピンを電圧に変換する新しい機能を発見. 京都大学プレスリリース. 2016-05-18.

著者

Suzuki K. Barbiellini B. Orikasa Y. Go N. Sakurai H. Kaprzyk S. Itou M. Yamamoto K. Uchimoto Y. Wang Yung Jui Hafiz H. Bansil A. Sakurai Y.

出版者

American Physical Society

雑誌

Physical Review Letters (ISSN:00319007)

巻号頁・発行日

vol.114, no.8, 2015-02-25

被引用文献数

41

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リチウムイオン二次電池の電池電極反応に寄与する電子軌道の解明 -マンガン酸リチウム系正電極材料設計に新たな指針-.京都大学プレスリリース. 2015-02-05.

著者

Kiuchi Kenta Kyutoku Koutarou Sekiguchi Yuichiro Shibata Masaru Wada Tomohide

出版者

American Physical Society

雑誌

Physical Review D (ISSN:15507998)

巻号頁・発行日

vol.90, no.4, 2014-08-28

被引用文献数

166

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連星中性子星の合体とブラックホールの進化過程に新解釈 -スーパーコンピュータ「京」で磁場の増幅機構が明らかに-. 京都大学プレスリリース. 2014-09-01.

著者

石原 純夫

出版者

American Physical Society

雑誌

Physical review. B

巻号頁・発行日

vol.66, no.1, pp.14435-1-014435-9, 2002

被引用文献数

15 12 9

著者

Hamamoto Yuji Kawarabayashi Tohru Aoki Hideo Hatsugai Yasuhiro

出版者

American Physical Society

雑誌

Physical review B (ISSN:10980121)

巻号頁・発行日

vol.88, no.19, pp.195141, 2013-11

被引用文献数

2 1

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Motivated by the recent experiments indicating a spin-unpolarized ν=0 quantum Hall state in graphene, we theoretically investigate the ground state based on the many-body problem projected onto the n=0 Landau level. For an effective model with the on-site Coulomb repulsion and antiferromagnetic exchange couplings, we show that the ground state is a doubly degenerate spin-resolved chiral condensate in which all the zero-energy states with up spin are condensed into one chirality, while those with down spin to the other. This can be exactly shown for an Ising-type exchange interaction. The charge gap due to the on-site repulsion in the ground state is shown to grow linearly with the magnetic field, in qualitative agreement with the experiments.

著者

Shimada Takahiro Ueda Taku Wang Jie Kitamura Takayuki

出版者

American Physical Society

雑誌

Physical Review B (ISSN:10980121)

巻号頁・発行日

vol.87, no.17, 2013-05

被引用文献数

63

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The nature of intrinsic point defects, i.e., energetic, ferroelectric, and electronic properties of vacancies in ferroelectric PbTiO_{3}, is studied using first-principles calculations based on the hybrid Hartree-Fock density functional, which correctly reproduces the band gap and thus provides the accurate defect electronic states. The oxygen vacancies are found to behave as double shallow donors and are thermodynamically stable over a wide range of Fermi levels under oxygen-poor conditions, while Pb vacancies are likely to be formed under oxygen-rich conditions and act as double shallow acceptors, which lead to p-type conductivity. The result shows good consistency with the relevant experimental observations. The ferroelectric distortion is disturbed anisotropically outward by oxygen vacancies and is characterized by localized defect electronic states contributed by d orbitals. In contrast, an isotropically inward ferroelectric disturbance is found around Pb and Ti vacancies. Such a ferroelectric disturbance is strongly enhanced by the charging of vacancies, except for Pb vacancies that induce delocalized defect states.

著者

Takatsu Hiroshi Ishikawa Jun J. Yonezawa Shingo Yoshino Harukazu Shishidou Tatsuya Oguchi Tamio Murata Keizo Maeno Yoshiteru

出版者

American Physical Society

雑誌

Physical Review Letters (ISSN:00319007)

巻号頁・発行日

vol.111, no.5, 2013-08

被引用文献数

89

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単純な金属を磁気センサーに応用できる新メカニズムの発見. 京都大学プレスリリース. 2013-07-31.

著者

Nemoto Yuya Hino Ken-ichi Maeshima Nobuya

出版者

American Physical Society

雑誌

Physical review B (ISSN:10980121)

巻号頁・発行日

vol.87, no.20, pp.205305, 2013-05

被引用文献数

5

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We examine a continuum effect of a dynamic Wannier-Stark ladder (DWSL) driven by a cw laser—with Fac and ω as amplitude and frequency, respectively—by means of an excess density of states (DOS), ρ(ex)(E), closely related to the more familiar DOS and proportional to the lifetime of a resonance state. It is mathematically shown that ρ(ex)(E) is governed by three different physical mechanisms: the single-channel resonance mechanism, the multichannel nonresonance mechanism, and the multichannel resonance mechanism. The last mechanism becomes more important with the increase in Fac. The effect of the interchannel interaction is maximized when the ratio of a Bloch frequency to ω, represented as η, equals unity. In the actual calculations based on the R-matrix Floquet theory, it is revealed that, in a large-Fac region, ρ(ex)(E) for η=1 shows a complicated spectral structure composed of a couple of newly growing peaks, in contrast to ρ(ex)(E) for η=3 which just shows a monotonic change of a single spectral peak. It is speculated that the pronounced feature of the former spectra is attributed to the Fano-like multichannel resonance mechanism, whereas the feature of the latter case is attributed to the multichannel nonresonance mechanism.

著者

Jizba Petr Arimitsu Toshihico

出版者

American Physical Society

雑誌

Physical review E (ISSN:15393755)

巻号頁・発行日

vol.69, no.2, pp.026128, 2004-02

被引用文献数

51 26

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Despite recent claims we argue that Rényi’s entropy is an observable quantity. It is shown that, contrary to popular belief, the reported domain of instability for Rényi entropies has zero measure (Bhattacharyya measure). In addition, we show that the instabilities can be easily emended by introducing a coarse graining into an actual measurement. We also clear up any doubts regarding the observability of Rényi’s entropy in (multi)fractal systems and in systems with absolutely continuous probability density functions.

著者

Arimitsu T. Arimitsu N.

出版者

American Physical Society

雑誌

Physical review E (ISSN:1063651X)

巻号頁・発行日

vol.61, no.3, pp.3237-3240, 2000-03

被引用文献数

86 110

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The analysis of the fully developed turbulence with the help of the binomial multiplicative process is reinvestigated from the standpoint of Tsallis nonextensive statistics in order to provide some insight in understanding the underlying physical meaning of the Tsallis ensemble. The formula is derived which relates Tsallis index q with the intermittency exponent μ that is a manifestation of multifractality of the sizes of eddies. It is shown that the probability density function of the local dissipation of turbulent kinetic energy can be represented by a distribution function of the type in Tsallis statistics with the index q determined by the experimentally observable quantity μ through the derived formula.

著者

Kobayakawa T. S. Hatsugai Y. Kohmoto M.

出版者

American Physical Society

雑誌

Physical review E (ISSN:1063651X)

巻号頁・発行日

vol.51, no.6, pp.5365-5370, 1995-06

被引用文献数

9 9

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Recently, the smoothed correlation between the density of eigenvalues of Hermitian random matrices was found to be universal, that is, independent of the probability distribution from which the random matrices are taken. We study this universal correlation numerically by ensemble averaging, using the Monte Carlo sampling method. Although the density of eigenvalues and the ‘‘bare’’ correlation between the density of eigenvalues are certainly not universal, we find that the smoothed correlation indeed shows a universal behavior. The orthogonal and the symplectic ensembles are also studied numerically. The smoothed correlation is shown to be universal in these cases.

著者

Arimitsu Toshihico Arimitsu Naoko

出版者

American Physical Society

雑誌

Physical review E (ISSN:1063651X)

巻号頁・発行日

vol.50, no.1, pp.121-137, 1994-07

被引用文献数

6 16

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A general formula of the time-resolved optical spectrum for transient resonant light scattering is derived systematically by means of the operator algebra within the formalism of nonequilibrium thermo field dynamics (NETFD). The formula is applied to an analytically solvable model of the localized electron and phonon system, i.e., second-order light scattering due to the optically active three electronic states whose intermediate state is dynamically modulated by the phonon interaction mode. The derivation of the analytical expression for a four-point function, needed to obtain the spectrum, is performed with the help of the algebraic manipulations in NETFD, which showed the advantage of its methodology with respect to nonequilibrium transient phenomena. The three-dimensional profiles of the Raman and luminescence components in the time-resolved spectrum in the model are presented to show how the stochastic character comes out in the fast modulation limit, and how the dynamical behavior of the phonon system causing the modulation of the intermediate electronic state comes out in the slow modulation limit.

著者

Nomura Shintaro Iitaka Toshiaki

出版者

American Physical Society

雑誌

Physical review E (ISSN:15393755)

巻号頁・発行日

vol.76, no.3, pp.037701, 2007-09

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A linear scale method for calculating electronic properties of large and complex systems is introducedwithin a local density approximation. The method is based on the Chebyshev polynomialexpansion and the time-dependent method, which is tested on the calculation of the electronicstructure of a model n-type GaAs quantum dot.

著者

Yoshida Kyo Kaneda Yukio

出版者

American Physical Society

雑誌

Physical review E (ISSN:1063651X)

巻号頁・発行日

vol.63, pp.016308, 2000-12

被引用文献数

17 20

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A model of randomly advected solenoidal field is presented. The model is formally derived by a linearization of the Navier-Stokes equation with respect to the perturbation to a basic state and by assuming the characteristic time scale of the basic state to be very short. The model includes a nonlocal (in space) effect through a pressurelike term that keeps the advected field solenoidal, but still yields exact equations for multipoint moments. The advecting field is assumed to be statistically homogeneous and isotropic with zero mean and structure function with exponent xi. An analysis is made of the scaling of the steady second-order moments of the solenoidal field in two dimensions. The scaling exponent zeta(l) of the isotropic part (l=0) and the anisotropic part for the angular wave number l=2 is obtained analytically or numerically. The scaling of the isotropic part does not depend on whether the pressurelike term is present or not while the scaling of the anisotropic part is affected by the pressurelike term. There are two homogeneous similarity solutions with real positive exponents zeta(2) when xi>xi(c)(2) approximately 1.3. The same kind of analysis is also applied to a simplified two-point closure equation.

著者

Tomimoto S. Matsubara M. Ogasawara T. Okamoto H. Kimura T. Tokura Y.

出版者

American Physical Society

雑誌

Physical review letters (ISSN:00319007)

巻号頁・発行日

vol.98, no.1, pp.017402, 2007-01

被引用文献数

17

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Optical manipulation of the magnetic anisotropy is demonstrated for bilayered manganites, La2-2xSr1+2xMn2O7, by means of femtosecond Kerr-rotation measurements. Upon the photoexcitation on the x=0.32 crystal, the magnetization exhibits the precessional motion for about 1 ns, revealing the directional change of the magnetocrystalline anisotropy from the c axis to the ab plane. This change of the anisotropy induces the nonthermal decrease of the c-axis magnetization component for about 1 ns.