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69 巻, 1 号
選択された号の論文の50件中1～50を表示しています
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Masayoshi Inoue, Masakazu Nagadome2000 年 69 巻 1 号 p. 1-4
発行日: 2000/01/01
公開日: 2000/07/28
ジャーナル 認証ありA coupled system composed of two cellular automata in which one is driven probabilistically by the other is studied. The coupled system has a critical coupling constant Pc. For P>Pc, the two automata are mutually synchronized with each other exhibiting a chaotic motion called Wolfram's class 3. Class 4-type motion is generated by a class 3 rule near the critical point, and the phenomenon of edge of chaos is characterized by the Langton λ parameter and mutual information.抄録全体を表示PDF形式でダウンロード (203K) -
Teruhisa S. Komatsu2000 年 69 巻 1 号 p. 5-8
発行日: 2000/01/01
公開日: 2000/07/28
ジャーナル 認証ありThe molecular dynamics of inelastic disks without external forcing is investigated. By introducing a special observation frame with rescaled time, we observe the virtual steady states converted from asymptotic energy dissipation processes. The system behavior in the thermodynamic limit is carefully investigated. It is found that a phase transition with symmetry breaking occurs when the magnitude of dissipation is greater than a critical value.抄録全体を表示PDF形式でダウンロード (170K) -
Takami Tohyama, Yasumasa Shibata, Sadamichi Maekawa, Z.–X. Shen, ...2000 年 69 巻 1 号 p. 9-12
発行日: 2000/01/01
公開日: 2000/07/28
ジャーナル 認証ありThe numerically exact diagonalization study on small clusters of the t-J model with second- and third-neighbor hopping terms shows that a novel spin liquid state is realized around a doped hole with momentum k =(π, 0) and energy --2J compared with that with (π/2, π/2) in insulating cuprates, where the spin and charge degrees of freedom are approximately decoupled. Our finding implies that the excitations in the insulating cuprates are mapped onto the d-wave resonating valence bond state.抄録全体を表示PDF形式でダウンロード (181K) -
Shoji Yamamoto2000 年 69 巻 1 号 p. 13-16
発行日: 2000/01/01
公開日: 2000/07/28
ジャーナル 認証ありBased on a symmetry argument, we study the ground-state properties of halogen-bridged binuclear metal chain complexes. We systematically derive commensurate density-wave solutions from a relevant two-band Peierls-Hubbard model and numerically draw the the ground-state phase diagram as a function of electron-electron correlations, electron-phonon interactions, and doping concentration within the Hartree-Fock approximation. The competition between two types of charge-density-wave states, which has recently been reported experimentally, is demonstrated.抄録全体を表示PDF形式でダウンロード (158K) -
Shunsuke Yoshii, Kazuhiro Murata, Masatoshi Sato2000 年 69 巻 1 号 p. 17-20
発行日: 2000/01/01
公開日: 2000/07/28
ジャーナル 認証ありTransport and magnetic properties of pyrochlore ruthenates R2-xBixRu2O7 (R=Sm and Eu), which exhibit the Mott insulator to metal transition with increasing x, have been studied. The electrical resistivity ρ and the Hall coefficient RH are found to strongly couple to the change of the magnetic state, or the transition to the spin-glass state which takes place at temperature T=TG. Near the metal-insulator phase boundary, RH above TG increases rather rapidly with decreasing T even in the metallic phase, and the Hall angle θH follows a simple relation, cot θH ∝ a+bT2, over the wide T-range. At T=TG, RH has a peak and it decreases with decreasing T. These results indicate that strong spin fluctuations above TG induce the anomalous T-dependence of RH in the present magnetically frustrated three-dimensional system and RH decreases as the spin freezing proceeds.抄録全体を表示PDF形式でダウンロード (198K) -
Kiminori Waku, Nigel E. Hussey, Fumiko Sakai, Minoru Nohara, Hidenori ...2000 年 69 巻 1 号 p. 21-24
発行日: 2000/01/01
公開日: 2000/07/28
ジャーナル 認証ありIn YBa2Cu4O8 (Y124), the c-axis resistivity ρc(T) shows a drastic change from metallic to insulating behavior above a crossover magnetic field Bcr ( B // a ), namely a magnetic field induced dimensional crossover. A simple picture for quasi-1-dimensional (quasi-1D) band transport along the CuO chains, originally proposed by Gorkov and Lebed, was suggested as the mechanism for this novel phenomenon. To further test the proposed picture, similar measurements on Y124 crystals doped with Zn were performed. Zn-doping is found to alter significantly ρc(T) at low temperatures but has little effect on the magnetic field induced dimensional crossover. These results are in good agreement with the predictions of the quasi-1D chain model and appear to confirm the critical role of the CuO chains in metallizing the c-axis in Y124.抄録全体を表示PDF形式でダウンロード (145K) -
Masanori Kohno, Masatoshi Imada2000 年 69 巻 1 号 p. 25-28
発行日: 2000/01/01
公開日: 2000/07/28
ジャーナル 認証ありWe investigate the effects of suppression of single-particle dispersion near the Fermi level on the spin gap and the singlet-pairing correlation by using the exact diagonalization method for finite-size systems. We consider strongly correlated one-dimensional models, which have flat band dispersions near wave number k=π/2, if the interactions are switched off. Our results for strongly correlated models show that the spin gap region expands as the single-particle dispersion becomes flatter. The region where the singlet-pairing correlation is the most dominant also expands in models with flatter band dispersions. Based on our numerical results, we propose a pairing mechanism induced by the flat-band dispersion.抄録全体を表示PDF形式でダウンロード (149K) -
Hikaru Kawamura2000 年 69 巻 1 号 p. 29-32
発行日: 2000/01/01
公開日: 2000/07/28
ジャーナル 認証ありThe stability of the three-dimensional vortex-glass order in random type-II superconductors with point disorder is investigated by equilibrium Monte Carlo simulations based on a lattice XY model with a uniform field threading the system. It is found that the vortex-glass order, which exists stably in the absence of screening, is destroyed by the screening effect, corroborating the previous finding based on the spatially isotropic gauge-glass model. Estimated critical exponents, however, deviate considerably from the values reported for the gauge-glass model.抄録全体を表示PDF形式でダウンロード (160K) -
Setsuo Mitsuda, Motoshi Mase, Takahiro Uno, Hideaki Kitazawa, Hiroko A ...2000 年 69 巻 1 号 p. 33-36
発行日: 2000/01/01
公開日: 2000/07/28
ジャーナル 認証ありBy magnetization and specific heat measurements in an applied magnetic field up to 12 T, we obtained the magnetic field (H) versus temperature (T) phase diagram of a frustrated triangular lattice antiferromagnet (TLA), CuFeO2, where a partially disordered phase typical to Ising TLA exists as a thermally induced state for the 4-sublattice ground state as well as for the first-field-induced 5-sublattice-like state. The experimentally obtained H-T magnetic phase diagram is compared with that from Monte-Carlo simulation of a 2D Ising TLA model with competing exchange interactions up to 3rd neighbors.抄録全体を表示PDF形式でダウンロード (320K) -
Nobuhisa Okazaki, Junji Miyoshi, Toru Sakai2000 年 69 巻 1 号 p. 37-40
発行日: 2000/01/01
公開日: 2000/07/28
ジャーナル 認証ありThe magnetization process of the S=1/2 antiferromagnetic spin ladder at T=0 is studied by the exact diagonalization of finite clusters and size scaling analyses. It is found that a magnetization plateau appears at half the saturation value (m=1/2) in the presence of a sufficiently large next-nearest-neighbor exchange interaction to yield the frustration, when the rung coupling is larger than the leg one. The phase diagram at m=1/2 is given by the analysis based on the conformal invariance. The magnetization curves are also presented in several cases.抄録全体を表示PDF形式でダウンロード (140K) -
Qihua Zhang, Michinobu Mino, Vladimir L. Safonov, Hitoshi Yamazaki2000 年 69 巻 1 号 p. 41-44
発行日: 2000/01/01
公開日: 2000/07/28
ジャーナル 認証ありMagnetic microwave parametric excitation of magnetoelastic waves in the easy-plane antiferromagnet FeBO3 is studied at room temperature. Measurements were performed at X-band with a perpendicular pumping configuration. We observed the saturation of the microwave absorption of antiferromagnetic resonance above the pumping threshold and simultaneous microwave radiation from the sample at half pump frequency. The radiation spectrum, its intensity dependence on the pumping power and magnetic field are investigated. The obtained results are in agreement with the fact that the radiation appears due to parametrically excited transverse quasiphonons propagating along the “hard” magnetic axis of a crystal.抄録全体を表示PDF形式でダウンロード (134K) -
Hon–Wah Tam, Wen–Xiu Ma, Xing–Biao Hu, Dao–Liu ...2000 年 69 巻 1 号 p. 45-52
発行日: 2000/01/01
公開日: 2000/07/28
ジャーナル 認証ありThe well-known Hirota-Satsuma coupled KdV equation and a coupled Ito system are reviewed. A new type of soliton solutions to these two systems under constant boundary condition at infinity is found. The so-called generalized Hirota-Satsuma coupled KdV system is also considered. Starting from its bilinear forms, we obtain a Bäcklund transformation and the corresponding nonlinear superposition formulae. As a result, soliton solutions first obtained by Satsuma and Hirota can be rederived. Moreover, rational solutions are also given.抄録全体を表示 -
Norio Inui, Genichi Komatsu, Koichi Kameoka2000 年 69 巻 1 号 p. 53-58
発行日: 2000/01/01
公開日: 2000/07/28
ジャーナル 認証ありIn order to study the solvability of the percolation model based on Guttmann and Enting's conjecture, the power series for the percolation probability in the form of ∑nHn(q)pn is examined. Although the power series is given by calculating inverse of the transfer-matrix in principle, it is very hard to obtain the inverse matrix containing many complex polynomials as elements. We introduce a new series expansion technique which does not necessitate inverse operation for the transfer-matrix. By using the new procedure, we derive the series of the asymmetrical percolation probability including the isotropic percolation probability as a special case.抄録全体を表示 -
Masataka Iwao, Ryogo Hirota2000 年 69 巻 1 号 p. 59-72
発行日: 2000/01/01
公開日: 2000/07/28
ジャーナル 認証ありThe multisoliton solution to a system of nonlinear partial differential equations which is expressed by frac ∂ vi ∂ t + 6∑1 ≤ j < k ≤ N Cjk ( frac ∂ vj ∂ x vk - vj frac ∂ vk ∂ x ) frac ∂ vi ∂ x + frac ∂ 3 vi ∂ x3 = 0, for i=1, 2, …, N where the coefficients Cjk are arbitrary constants, is expressed by the pfaffians.抄録全体を表示 -
Sachiko Kitajima, Fumiaki Shibata2000 年 69 巻 1 号 p. 73-87
発行日: 2000/01/01
公開日: 2000/07/28
ジャーナル 認証ありDecoherence and relaxation processes in quantum systems are studied on the basis of an exactly solvable model. That is, a generalized Coleman-Hepp model is analyzed in a framework of a spin coherent state representation which enables us to determine time evolution of the whole system as successive applications of rotation operators. A density matrix of the whole system and reduced density matrices of constituent subsystems are obtained to yield quasi-probability densities and averages of observables of an incident particle and a detector (reservoir) system. Numerical evaluation of these quantities is performed to find decoherence like phenomena for larger values of N (a number of detector spins) and Sl (magnitude of a detector spin). An appearance of a mixed state (i.e., vanishing of off-diagonal elements of a reduced matrix) is explicitly shown when N and/or Sl become infinity. Namely, this occurs in the thermodynamic limit (N → ∞) and/or in the classical apparatus limit (Sl → ∞).抄録全体を表示 -
Yup Kim, C. K. Lee2000 年 69 巻 1 号 p. 88-91
発行日: 2000/01/01
公開日: 2000/07/28
ジャーナル 認証ありTwo kinds of conserved growth models in which a deposited particle moves to a randomly chosen nearest neighbor column under a certain condition are studied. The conditions to permit such relaxations are similar to those in Family model and in Krug model. Both models are shown to follow the Mullins-Herring (MH) equation. From the studies of the suggested models, the new critical growth processes which discriminate MH universality from Edwards-Wilkinson (EW) universality are found. Possible implications of these critical processes to the other growth models are also discussed.抄録全体を表示 -
Toyonori Munakata, Sadahito Mitsuoka2000 年 69 巻 1 号 p. 92-96
発行日: 2000/01/01
公開日: 2000/07/28
ジャーナル 認証ありDynamics for a generalized thermodynamics due to Tsallis is formulated based on a new Langevin equation, with classical driving force and nonclassical multiplicative noise. As applications, the Kramers problem (thermal activation rate over a potential barrier) and anomalous Brownian motion are considered within the framework of the generalized thermodynamics. The dynamics is generalized further by treating temperature as a stochastic variable, leading to a Langevin formulation of simulated tempering for efficient Monte-Carlo sampling and optimization.抄録全体を表示 -
Takeya Tsurumi, Miki Wadati2000 年 69 巻 1 号 p. 97-103
発行日: 2000/01/01
公開日: 2000/07/28
ジャーナル 認証ありWe investigate the dynamics of magnetically trapped boson-fermion mixtures at very low temperature. Using the mean field approach, we derive the Gross-Pitaevskii equation for the Bose-Einstein condensate wavefunction. We apply the Thomas-Fermi approximation and the hydrodynamic approach to the degenerate Fermi gas and obtain an equation of motion for its number density perturbation. It is remarkable that coupled time-evolution equations for the mixture can be regarded as an extension of the Zakharov equations, a model for the Langmuir waves in plasma.抄録全体を表示 -
Hidetsugu Sakaguchi2000 年 69 巻 1 号 p. 104-108
発行日: 2000/01/01
公開日: 2000/07/28
ジャーナル 認証ありA stationary nonequilibrium state for the Feynman ratchet is realized in a Langevin simulation with a stochastic boundary condition. We calculate the temporal fluctuation of the total entropy production and show that the “fluctuation-theorem” is valid for this stochastic system. An Einstein relation between the diffusion constant and the response coefficient is numerically verified.抄録全体を表示 -
Rafael G. Akopdzhanov2000 年 69 巻 1 号 p. 109-111
発行日: 2000/01/01
公開日: 2000/07/28
ジャーナル 認証ありThis paper is devoted to the use of Cu K X-ray emission and absorption spectroscopy in the investigation of the electronic structure of copper complexes. Cu Kβ5 X-ray fluorescent and X-ray absorption near edge structure (XANES) spectra of copper atom in copper arylthreeazene molecule (CuAtha) before and after introduction of four terminal methyl substituents CuAtha(CH3)4 were experimentally measured with high resolution. The effective copper charges in both molecules were determined from the analyses of Cu K XANES spectra. It was found that the metal ligand (Me-L) bonds in CuAtha molecule have a high degree of covalency and after introduction of four terminal CH3 substituents the covalency of Me-L bonds increases and the electron density on the central copper atom increases by 0.07 atomic units (a.u.) of charge. From the analyses of the low energy side structure of Cu Kβ5 spectra it was found that π “ligand” (π “L”) electron density in the vicinity of chelate node of CuAtha molecule increased more than σ “ligand” (σ “L”) electron density after introduction of the terminal CH3 substituents.抄録全体を表示 -
Jin–Seok Jeon, Ik–Jun Yang, Jung–Hee Na, Ho–Yo ...2000 年 69 巻 1 号 p. 112-119
発行日: 2000/01/01
公開日: 2000/07/28
ジャーナル 認証ありA mechanism of light emission from a single bubble sonoluminescence (SBSL) was formulated by assuming that the source for the light emission is bremsstrahlung in partially ionized gases. This emission mechanism turns out to be same as the black body radiation with finite absorption, which confirms that the principal mechanism of SBSL is bremsstrahlung with slight black body emission nature. Also the spectrum was measured and the observed results were compared with the calculated ones. Calculated and experimental results yield common spectral behavior in the visible region: the spectral radiance shows power-law dependence on wavelength with an exponent of - 2.5. The SBSL spectrum which is characterized by the continuous one with no major peaks has been confirmed experimentally. The bubble dynamics model proposed also takes account the afterpulse characteristics of SBSL.抄録全体を表示 -
Kazuyuki Domon, Osamu Ishihara, Shinsuke Watanabe2000 年 69 巻 1 号 p. 120-123
発行日: 2000/01/01
公開日: 2000/07/28
ジャーナル 認証ありMass transport by a vortex ring in water has been studied experimentally. A vortex ring with the Reynolds number in the vicinity of -- 1× 105 is launched in water by means of an exploding wire. Fine particles injected into a vortex ring at the outlet of vortex driver are carried away with vortex motion. Some particles spin out of the vortex motion and are left behind a vortex ring. But many of them are trapped in a vortex ring and are carried up to the end of water tank which is located at 1.4 m from the vortex driver. Mass analyses of particles show that particles with specific gravity of larger than unity are scattered out of a vortex ring due to a centrifugal force, but those with specific gravity being less than unity are trapped in a vortex core and are carried for a long distance. The result indicates that an efficient mass transport by a vortex ring is realized when the specific gravity of particles is less than that of ambient fluid that supports a vortex ring.抄録全体を表示 -
Jun–ichiro Suda, Mitsugu Matsushita, Kunihide Izumi2000 年 69 巻 1 号 p. 124-129
発行日: 2000/01/01
公開日: 2000/07/28
ジャーナル 認証ありWe have found that the crystals of rubidium dichromate (Rb2Cr2O7) grown in gelatin gel have a rich variety of morphologies such as platelike, spherulitic and diffusion-limited aggregation (DLA)-like shapes. The morphological diagram has been determined in the range of solute and gelatin concentrations from 1.0 to 4.0%, 0.1 to 7.0%, respectively. The diagram corresponds to that of potassium dichromate (K2Cr2O7) which is similar to Rb2Cr2O7 in the crystal structure and physico-chemical properties. However, featherlike crystals have grown in the region of the diagram where the unique helical K2Cr2O7 crystals grow. We discuss the morphological changes of two kinds of dichromate crystals grown in gelatin gel.抄録全体を表示 -
Daniil G. Sannikov, Grigorii A. Kessenikh, Hiroyuki Mashiyama2000 年 69 巻 1 号 p. 130-134
発行日: 2000/01/01
公開日: 2000/07/28
ジャーナル 認証ありA phenomenological approach for construction theoretical phase diagrams with multiple phase transitions including incommensurate transitions is developed for the case when a special triple point, a Lifshitz-type point, is assumed to be present in the experimental diagram for N(CH3)4 2ZnCl4 crystal family. The theoretical temperature-pressure phase diagram for N(CH3)4 2ZnCl4 is plotted and is found to be in agreement with the experimental phase diagram. The approximations and assumptions made in the construction of the diagrams are discussed.抄録全体を表示 -
Kiyoshi Deguchi, Yutaka Iwata2000 年 69 巻 1 号 p. 135-138
発行日: 2000/01/01
公開日: 2000/07/28
ジャーナル 認証ありThe effects of deuteration on the ferroelectric phase transition of LiTlC4H4O6·H2O (LTT) have been studied through dielectric measurements. The phase transition temperature Tc decreases with increasing concentration of deuterium in the crystal, and vanishes in the highly deuterated crystal. On the other hand, the Curie-Weiss constant C remains almost constant with deuteration. The decreasing and vanishing of Tc with a finite C in deuterated LTT is attributed to the phase transition mechanism of displacive-type.抄録全体を表示 -
Tadao Ishii2000 年 69 巻 1 号 p. 139-148
発行日: 2000/01/01
公開日: 2000/07/28
ジャーナル 認証ありThe theory of ion-hopping conduction in a classical lattice liquid, the interacting lattice gas, in the context of the master equation is developed in terms of newly introduced number operators which are consistent with the lattice gas statistics. An explicit equation of many-body probability thus acquired is utilized in averaging physical quantities. One of the main applications is forwarded to the development of the relaxation mode theory for the noninteracting lattice gas particles on any lattice structure. The other application is to obtain a hierarchy of equations, and to confirm the coupled equations derived from the pair approximation of the path probability method under the nearest-neighbor interaction. The method proceeded in the text holds for the Coulomb interaction case as well.抄録全体を表示 -
Yasumasa Tsukamoto, Norio Kawakami2000 年 69 巻 1 号 p. 149-154
発行日: 2000/01/01
公開日: 2000/07/28
ジャーナル 認証ありWe study the critical properties of one-dimensional electron systems with the 1/rα-type long-range interaction (α ≥ 1). Using bosonization methods, we discuss how the 1D system exhibits a crossover from the Tomonaga-Luttinger liquid to the Wigner crystal when α → 1. In particular, a detailed analysis is given to the Fermi-edge singularity phenomena when a mobile core hole is created suddenly in the valence band. It is found that the effect due to the core-hole motion on the Fermi-edge singularity is gradually suppressed as the system approaches the Wigner crystal, and its critical behavior is dominated by the ordinary impurity forward-scattering inherent in a static hole.抄録全体を表示 -
Akinori Hoshikawa, Kazushige Nomura, Satoshi Takasaki, Jun–ichi ...2000 年 69 巻 1 号 p. 155-159
発行日: 2000/01/01
公開日: 2000/07/28
ジャーナル 認証ありWe have performed the electric conductivity measurements in the spin-density-wave (SDW) phase of (TMTSF)2ClO4 to clarify the dynamics of SDW. The temperature dependence of threshold electric field ET associated with the depinning of SDW was investigated with changing the SDW transition temperature TSDW by the control of anion ordering. The steep temperature dependence was observed for the highest TSDW (6 K) and was explained with the weak pinning by the impurity. The temperature dependence of ET becomes moderate with decreasing TSDW. For TSDW=4 K, it is understood with the strong pinning. The crossover of pinning mechanism from the weak pinning to the strong one was discussed with taking account of the effective impurity concentration due to the disordered array of anion orientation.抄録全体を表示 -
Mamoru Sakaue, Hideaki Kasai, Ayao Okiji2000 年 69 巻 1 号 p. 160-169
発行日: 2000/01/01
公開日: 2000/07/28
ジャーナル 認証ありThe effect of Coulomb interactions between electrons on time-resolved two-photon photoemission from a metal surface is investigated theoretically. It is shown by nonequilibrium perturbation theory that the correlation trace (photoelectron intensity as a function of the pump-probe delay time) depends on lifetimes of both photoexcited electrons and holes due to the effect of Coulomb interactions. The numerical results of the correlation trace reproduce the qualitative features of the experimental results.抄録全体を表示 -
Makoto Ambai, Yukio Yasui, Jun Takeda, Yoshiaki Kobayashi, Masatoshi S ...2000 年 69 巻 1 号 p. 170-177
発行日: 2000/01/01
公開日: 2000/07/28
ジャーナル 認証ありSuperconducting transition temperatures Tc and their pressure dependence of Y1-xPrxBa2Cu3O6+y and Sm1-xPrxBa2Cu3O6+y have been studied. Transport studies and NQR/NMR measurements on Y1-xPrxBa2Cu3O6+y have also been carried out for various values of x and y. Anomalous dip-structure has been confirmed to appear, with increasing Pr concentration x, in the Tc-y curves drawn for fixed x values in both systems. However, in the Hall coefficients and the thermoelectric powers of the Pr-doped systems, we have not found any anomalous behavior which indicates the existence of the “stripe ordered” phase even for the samples located within the dip region of the Tc-y curve, exhibiting a clear contrast with the cases of La2-xBaxCuO4 and La2-x-yNdySrxCuO4. Instead, it is shown that the dip-structure can basically be explained as the result of both the reduction of the conducting holes due to the hole-trapping by the Pr4f-O2pπ hybridized orbits and the pair breaking by the trapped holes.抄録全体を表示 -
Satoshi Nakamura2000 年 69 巻 1 号 p. 178-189
発行日: 2000/01/01
公開日: 2000/07/28
ジャーナル 認証ありWe calculate self-consistently the Green's function and dynamical spin susceptibility on the basis of the self-consistent renormalization (SCR) theory for the two-dimensional single-band Hubbard model near half-filling. Not only the vertex corrections to the susceptibility but also those to the self-energy are incorporated in our theory. We find that the peak positions in the spectral density of dynamical spin susceptibility are shifted to the antiferromagnetic wave vector Q due to the effect of the vertex corrections. The particle-particle irreducible vertex in the linearized gap equation is approximated by the maximally crossed diagrams generated by the bare interactions and the interactions resulting from the spin fluctuations. The vertex corrections enhance both the self-energy correction and the effective pairing potential in the dx2-y2 channel. As a result, higher superconducting transition temperatures than in the fluctuation exchange (FLEX) approximation without vertex correction are reached in a wide doping range despite the strong pair breaking effect due to the self-energy correction. The pairing symmetry of dx2-y2 is always realized.抄録全体を表示 -
Takuya Okabe2000 年 69 巻 1 号 p. 190-193
発行日: 2000/01/01
公開日: 2000/07/28
ジャーナル 認証ありWe evaluate vertex corrections to Tc on the basis of the antiferromagnetic spin-fluctuation model of the high-Tc superconductivity. It is found that the corrections are attractive in the dx2-y2 channel, and they become appreciable as we go through an intermediate-coupling regime of Tc~= 100 K, the maximum Tc attainable in the one-loop Éliashberg calculation.抄録全体を表示 -
Critical Temperature, Critical Current, and Vortex Loops in 3D Anisotropic Josephson Junction ArraysChikao Kawabata, Masaki Takeuchi, Subodh R. Shenoy, Alan R. Bishop2000 年 69 巻 1 号 p. 194-202
発行日: 2000/01/01
公開日: 2000/07/28
ジャーナル 認証ありMonte Carlo simulations of a 3D anisotropic Josephson junction array are performed, to determine the critical temperature Tc(I, α) for the onset of phase incoherence. Here I is the external current drive at opposite surfaces, and α≡ EJ⊥/EJ// is the inter-/intra-layer Josephson coupling ratio. Tc(I, α) is equivalent to a critical current, Ic(T, α) for the breakdown of global phase coherence. The temperature and anisotropy dependence of Ic(T, α) supports a physical picture of two vortex populations, quasi-2D and 3D in nature at small and large scales respectively, separated by a length scale r⊥-- 1/√ α .抄録全体を表示 -
Takeo Kato, Masatoshi Imada2000 年 69 巻 1 号 p. 203-212
発行日: 2000/01/01
公開日: 2000/07/28
ジャーナル 認証ありThermodynamics and transport properties of resistance-shunted Josephson junctions are studied theoretically in the tight-binding limit EC/EJ << 1, where EC and EJ are a charging energy and a Josephson coupling energy respectively. Based on a phenomenological harmonic-oscillator model, weak coupling region K=RQ/R << 1 is analytically studied, where R and RQ=h/(2e)2 are a shunt resistance and the quantum resistance. In addition to an effective bandwidth 2 (h/2π) Δeff, we find that this multi-level system genuinely has a novel crossover at lower energy K (h/2π) Δeff below which the density of states becomes strongly degenerate. These two energy scales control the linear DC responses, optical responses, and nonlinear I-V characteristics. The lower energy crossover indicates the existence of a new class of strongly-correlated phenomena beyond the framework of the Kondo problem.抄録全体を表示 -
Shozo Takeno2000 年 69 巻 1 号 p. 213-218
発行日: 2000/01/01
公開日: 2000/07/28
ジャーナル 認証ありExamining solutions to equations for the gauge-invariant phase difference of macroscopic superconducting wavefunctions and comparing them with experimental data for the I--V characteristics of the intrinsic Josephson effect in high-Tc superconductors, we show the concrete evidence for the existence of nonlinear rotating modes which are a kind of intrinsic nonlinear localized modes in pure nonlinear lattices.抄録全体を表示 -
Keiichi Koyama, Tsuneaki Goto, Takeshi Kanomata, Ryunosuke Note, Yoshi ...2000 年 69 巻 1 号 p. 219-224
発行日: 2000/01/01
公開日: 2000/07/28
ジャーナル 認証ありThe magnetization process of FeSi has been measured with a high-quality single-crystalline sample using a SQUID magnetometer in the temperature range from 5 K to 600 K. From the Arrott plots of the magnetization data, the fourth-order coefficient of the free energy is found to have a large positive value at low temperature and significantly decreases by the order of 105 with increasing temperature. This result can be explained with a new spin fluctuation theory of FeSi proposed by Takahashi.抄録全体を表示 -
Yoshihiro Yamada, Keisei Kuroda, Ken–ichi Matono, Akihiko Sakata2000 年 69 巻 1 号 p. 225-229
発行日: 2000/01/01
公開日: 2000/07/28
ジャーナル 認証ありThe C14 Laves phase TiFe2 is an antiferromagnet with a Néel temperature around room temperature. The magnetic properties of the Al substituted system of TiFe2 have been investigated using magnetisation and NMR measurements. It has been found that antiferromagnetism in TiFe2 is suppressed by the Al substitution in x < 0.1, while ferromagnetism appears for 0.1 < x < 0.5. At x = 0.1 ferro- and antiferromagnetism coexist at low temperatures.抄録全体を表示 -
Preparation and Magnetic Properties of EuO Thin Films Epitaxially Grown on MgO and SrTiO3 SubstratesNobuyuki Iwata, Govind Pindoria, Tadataka Morishita, Kay Kohn2000 年 69 巻 1 号 p. 230-236
発行日: 2000/01/01
公開日: 2000/07/28
ジャーナル 認証ありFerromagnetic EuO films were epitaxially grown on MgO and SrTiO3 substrates aligned with EuO[100]//MgO[100], EuO(001)//MgO(001) and EuO[100]//SrTiO3[110], EuO(001)//SrTiO3(001). The single phase EuO film was obtained on MgO substrate. The higher order oxides, Eu2O3, was always present in the films on SrTiO3 substrate due to the reaction of europium metal and grown EuO with oxygen in SrTiO3. The optimized flux ratio of oxygen to europium, JOXY/JEu, was 0.39, for JEu=2.83× 1013 cm-2…-1. The representative growth rate was 9.0× 10-2 Å/s on MgO. Magnetic moment per europium atom was 6.9± 0.3 μB. The Curie temperature was 69 K for films on MgO. The TC higher than 69 K was observed for films on SrTiO3 thicker than 50 Å. The thickness of 400 Å was enough for the coercive field to be as low as 50 Oe.抄録全体を表示 -
Wei Chen, Kazuo Hida, Bryan Clifford Sanctuary2000 年 69 巻 1 号 p. 237-241
発行日: 2000/01/01
公開日: 2000/07/28
ジャーナル 認証ありOne dimensional S=1 antiferromagnetic Heisenberg chains with bond alternation and uniaxial single-ion-type anisotropy are studied by numerical exact diagonalization of finite size systems. We calculate the ground state phase diagram using the twisted boundary condition method for D≥q 0. The ground states of this model contain the Haldane state, large-D state and the dimer state. Using conformal field theory and the level spectroscopy method, we calculate the D and δ-dependence of the Luttinger liquid paraments K and the critical exponent ν of the energy gap.抄録全体を表示 -
Yasufumi Yamashita, Naokazu Shibata, Kazuo Ueda2000 年 69 巻 1 号 p. 242-247
発行日: 2000/01/01
公開日: 2000/07/28
ジャーナル 認証ありWe numerically study the SU(2) otimesSU(2) symmetric spin-orbit coupled model as a lower symmetric generalization of the SU(4) exchange model. On the symmetric line with respect to the spin and orbit, our result shows the essentially singular gap formation in consistent with the analytic approach, which is different from the previous numerical calculation. Furthermore, we find a new critical phase around the SU(4) point, surrounding the previously known gapless symmetric line. In the novel phase spin or orbital excitations around momentum q=π form massless continua which split from the excitations belonging to the [22] irreducible representation at the SU(4) point. Near the critical symmetric line, the additional coupled spin-orbit excitations around q=π/2 originating from [2112] become the lowest.抄録全体を表示 -
Mahdi S. Lataifeh2000 年 69 巻 1 号 p. 248-250
発行日: 2000/01/01
公開日: 2000/07/28
ジャーナル 認証ありMagnetization measurements were carried on the alloy system Fe1-xCox, the results confirm that the system have low anisotropy. The saturation magnetization Ms and the iron magnetic moment μFe increases with cobalt concentration, while the mean magnetic moment per formula exhibit a peak at around x= 0.4--0.5. These results are explained in terms of the electronic occupancy of 3d-band in Fe.抄録全体を表示 -
Xiao–Man Wang, Heng Fan, Xi–Wen Guan2000 年 69 巻 1 号 p. 251-258
発行日: 2000/01/01
公開日: 2000/07/28
ジャーナル 認証ありThe one-dimensional small-polaron model with open boundary conditions is considered in the framework of the quantum inverse scattering method. The spin model which is equivalent to the small-polaron model is the Heisenberg XXZ spin chain in an external magnetic field. For spin model, the solutions of the reflection equation (RE) and the dual RE are obtained. The eigenvalues and eigenvectors problems are solved by using the algebraic Bethe ansatz method. The case of the fermion model is also studied, the commuting of the transfer matrix can be proved, and the eigenvalues and the Bethe ansatz equations for fermion model are obtained.抄録全体を表示 -
Toshiya Hikihara, Makoto Kaburagi, Hikaru Kawamura, Takashi Tonegawa2000 年 69 巻 1 号 p. 259-266
発行日: 2000/01/01
公開日: 2000/07/28
ジャーナル 認証ありThe ground-state phase diagram of frustrated S = 1 XXZ spin chains with the competing nearest- and next-nearest-neighbor antiferromagnetic couplings is studied using the infinite-system density-matrix renormalization-group method. We find six different phases, namely, the Haldane, gapped chiral, gapless chiral, double Haldane, Néel, and double Néel (uudd) phases. The gapped and gapless chiral phases are characterized by the spontaneous breaking of parity, in which the long-range order parameter is a chirality, κ l=SlxSl+1y-SlySl+1x, whereas the spin correlation decays either exponentially or algebraically. These chiral ordered phases appear in a broad region in the phase diagram for Δ < 0.95, where Δ is an exchange-anisotropy parameter. The critical properties of phase transitions are also studied.抄録全体を表示 -
Masaki Maeda, Masayoshi Takagi, Ikuo Suzuki2000 年 69 巻 1 号 p. 267-275
発行日: 2000/01/01
公開日: 2000/07/28
ジャーナル 認証ありPottasium iodate, KIO3, belongs to the perovskite structure and undergoes successive phase transitions at T1= 212°C, T2= 72.5°C, T3=-15°C, T4=-160°C and T5=-240°C, respectively. The temperature dependences of the dielectric, elastic and piezoelectic properties have been measured in the temperature range from -263°C to 330°C. The superionic conductivity was found in the temperature range above T2. Pronounced dielectric dispersions in the frequency range below 10 kHz were observed around -160°C and -240°C and the data were analyzed by fitting to the Davidson-Cole and Havriliak-Negami dispersion formulas, respectively. Both dielectric anomalies are ascribed to the orientaional glass-transitions. The piezoelectric and elastic properties have been investigsated by the resonance-antiresonance method. The piezoelectric and elastic anomalies were observed at T2 and T3.抄録全体を表示 -
Yuqing Wang, Z. D. Wang, W. Wang2000 年 69 巻 1 号 p. 276-283
発行日: 2000/01/01
公開日: 2000/07/28
ジャーナル 認証ありIn the presence/absence of external noise, dynamical behaviors of periodically forced neural systems and firing modes of interspike interval (ISI) are investigated by employing the Hindmarsh-Rose model. In the biologically relevant range of the forcing frequency, the interplay among the intrinsic oscillation, the forcing oscillation, and the noise leads to three kinds of firing modes: multi-modal firing, bi-modal firing, and intrinsic oscillation, in terms of which we can roughly classify the relevant experimental observations on the periodically forced sensory neural systems through their dynamical status. The resonant feature of subthreshold intrinsic oscillations shown in the ISI, the output signal-to-noise ratio, and the mean firing rate, appears to be an indication of stochastic resonance (SR) without external noise, or the `intrinsic' SR. In the multi-modal firing region where SR leads to the skipping phenomenon, based on the `intrinsic' SR, a possible explanation of a specific ISIH observed in experiments is given. Moreover, a neural system can tune itself to be chaotic to encode the weak signal, rather than relying only on the external noise.抄録全体を表示 -
Hari Prakash, Ravi S. Singh2000 年 69 巻 1 号 p. 284-285
発行日: 2000/01/01
公開日: 2000/07/28
ジャーナル 認証ありFor monochromatic light propagating along z-direction, we define a polarization operator which is product of inverse annihilation operator for the x-linearly polarized mode and the annihilation operator for the y-linearly polarized mode. This polarization operator is helpful in testing whether light in a given state is perfectly polarized, and in knowing this perfect polarized state.抄録全体を表示 -
Tetsuji Kume, Masahito Daimon, Shigeo Sasaki, Hiroyasu Shimizu2000 年 69 巻 1 号 p. 286-287
発行日: 2000/01/01
公開日: 2000/07/28
ジャーナル 認証あり -
Takefumi Yamada, Junko Hatori, Fumihito Shikanai, Masaru Komukae, Tosh ...2000 年 69 巻 1 号 p. 288-289
発行日: 2000/01/01
公開日: 2000/07/28
ジャーナル 認証あり -
Hiroshi Ito, Takehiko Ishiguro, Tetsuo Kondo, Gunzi Saito2000 年 69 巻 1 号 p. 290-291
発行日: 2000/01/01
公開日: 2000/07/28
ジャーナル 認証あり -
Yutaka Nakai, Yorihiko Tsunoda2000 年 69 巻 1 号 p. 292-293
発行日: 2000/01/01
公開日: 2000/07/28
ジャーナル 認証あり
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