Journal of the Physical Society of Japan
Online ISSN : 1347-4073
Print ISSN : 0031-9015
ISSN-L : 0031-9015
Volume 70, Issue 11
Displaying 1-46 of 46 articles from this issue
  • Yutaka Nishi, Ayumi Setoyama, Masayoshi Inoue
    Article type: General Physics
    Subject area: Mathematical methods in physics.
    2001 Volume 70 Issue 11 Pages 3189-3192
    Published: 2001
    Released on J-STAGE: February 28, 2003
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    We study chaos synchronization using a nonperturbative method, where coupled logistic maps xn+1=f(xn)+D[yn+1-xn+1]; yn+1=f(yn)+D[xn+1-yn+1] with f(x)=ax(1-x) are considered. We prove theoretically that any initial points eventually synchronize if D>(a-3)/2; (a>3), where mapping of the full phase space is considered instead of tracing an orbit of one initial point. Particularly when a=4, D>0.5 is the necessary and sufficient condition for the synchronization. A significant disadvantage inherent in a conventional linear stability theory is also discussed.
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  • Il-Tong Cheon
    Article type: General Physics
    Subject area: Mathematical methods in physics.
    2001 Volume 70 Issue 11 Pages 3193-3196
    Published: 2001
    Released on J-STAGE: February 28, 2003
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    The line width of the first excited state of 133Cs has been measured using the Mössbauer method. Our gamma ray source was 133BaTiO3 in free space. When the absorber, CsCl, was placed between two parallel flat plates, narrowing of the net width by as much as 8.7% was observed for the plate separation distance b=2.13 mm. This result implies that the lifetime of the 81 keV energy level of 133Cs is increased to 6.87 ± 0.11 ns. This value is 9.6% larger than the standard value of 6.27 ±0.02 ns.
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  • Naoaki Miyato, Satoshi Hamaguchi, Masahiro Wakatani
    Article type: General Physics
    Subject area: Mathematical methods in physics.
    2001 Volume 70 Issue 11 Pages 3197-3200
    Published: 2001
    Released on J-STAGE: February 28, 2003
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    In a currentless plasma, there are many unstable drift-Alfvén modes with different radial eigenfunctions with fixed poloidal and toroidal mode numbers, m and n, respectively. When growth rates of unstable modes are plotted as a function of total plasma current Ip, two opposite tendencies, stabilization and destabilization, are seen with the increase of Ip. When two eigenvalues (ωrjij) and (ωrj+1ij+1), where j denotes the order of the eigenvalue from the largest one, for given m and n become close at Ip∼eq Ic in a large current regime, the real frequencies do not cross. However, sometimes the two growth rates cross or ωijij+1 occurs, although the real frequencies satisfy ωrjrj+1. The eigenfunctions of the resistive drift-Alfvén mode with (ωrjij) at Ip≤ Ic are similar to those with (ωrj+1ij+1) at Ip≥ Ic, where ωrjrj+1. These unstable modes may affect the magnetic spectrum of the drift-Alfvén frequency range.
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  • Yoshifumi Saitou, Akira Tsushima
    Article type: General Physics
    Subject area: Mathematical methods in physics.
    2001 Volume 70 Issue 11 Pages 3201-3204
    Published: 2001
    Released on J-STAGE: February 28, 2003
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    The relationship of ion-flux ratio and electric current with plasma flow has been investigated using the one-dimensional particle-in-cell simulation. The internal region between a pair of face-to-face electrodes, which are electrically connected to each other, is filled with a plasma diffused from an external flowing plasma with Mach number M ≤ 2. The ion-flux ratio of the upstream and downstream electrodes agrees with the prediction of the Stangeby fluid model for M ≤ 1.2, and is higher than the prediction for larger M. The electric current linearly increases with increasing M for M ≤ 1 and reaches the maximum value at M ∼ 1.7. The dependence of the electric current on the Mach number is partly explained by the double probe theory.
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  • Hiroya Ishikawa, Takashi Itoh, Masato Hashimoto
    Article type: General Physics
    Subject area: Mathematical methods in physics.
    2001 Volume 70 Issue 11 Pages 3205-3208
    Published: 2001
    Released on J-STAGE: February 28, 2003
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    The temperature dependence of crystal structure and specific heat is measured at normal pressure and/or high pressures for nylons with a hexamethylene moiety (nylons 62, 66, 68, 48 and 7). First-order phase transition occurs in the as-synthesized nylon 62 crystal at normal pressure. First- and second-order phase transitions are observed in the solution-crystallized nylon 68 crystal under elevated pressures similarly to nylon 66, and while the structural change of nylon 48 and 7 crystals is gradual, no phase-transitional phenomena are observed. Such results suggest that the hexamethylene moiety between NH groups plays an intrinsic role in phase transition, and that the moiety between CO groups does not seem to contribute to the phase-transitional aspect in nylon crystals due to rotational hindrance around the (CO)-C bond.
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  • Hiroya Sakurai, Kazuyoshi Yoshimura, Koji Kosuge, Akihiro Mitsuda, Tsu ...
    Article type: General Physics
    Subject area: Mathematical methods in physics.
    2001 Volume 70 Issue 11 Pages 3209-3212
    Published: 2001
    Released on J-STAGE: February 28, 2003
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    A powder sample of KCu5V3O13 was synthesized and is expected to represent a novel frustrated spin chain system based on its characteristic crystal structure. The magnetic susceptibility and the high-field magnetization process were investigated in order to elucidate the ground state of this spin chain system. From the results, the ground state of this compound appears to be an antiferromagnetically ordered state. The transition temperature was determined to be TN=7.8 K. However, there are some anomalous behaviors evident in both the susceptibility and the magnetization curves: the Curie constant and the Weiss temperature change markedly around 75 K, the gradient of the magnetization curve becomes small after a spin-flop transition, and the number of the ordered spins is only 1/5 of all the copper spins. Assuming that the other spins vanish by forming a spin-singlet state, the energy gap was estimated to be 44.3 K from the magnetization curve. Thus, the classical renormalized ordered state may coexist with the quantum disordered state. Two conceivable models have been proposed for the ground state.
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  • Kiyoko Yamanaka, Ruiping Wang, Mitsuru Itoh, Katsunori Iio
    Article type: General Physics
    Subject area: Mathematical methods in physics.
    2001 Volume 70 Issue 11 Pages 3213-3216
    Published: 2001
    Released on J-STAGE: February 28, 2003
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    An optical birefringence study was performed on the quantum ferroelectric phase transition in the oxygen isotope exchanged system SrTi(16O1-x18Ox)3. The ferroelectric ordering in (110)c plates with the substitutional ratio x>0.33 brought about a marked enhancement in the temperature dependence of birefringence. The temperature derivative of the birefringence had a singularity at a temperature which can be regarded as the ordering temperature Tc. The antiferrodistortive phase transition temperature Ta of a (110)c sample with x=0.86 reached 107.7 K. The (001)-plane birefringence of a (110)c sample with x=0.83 exhibited a slight, but clear change at Tc.
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  • Takashi Teramoto
    Article type: General Physics
    Subject area: Mathematical methods in physics.
    2001 Volume 70 Issue 11 Pages 3217-3220
    Published: 2001
    Released on J-STAGE: February 28, 2003
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    Application of the Saeki method [J. Phys. Soc. Jpn. 69 (2000) 679] to copolymer-homopolymer mixtures using the free energy proposed by Ohta and Ito [Phys. Rev. E 52 (1995) 5250] reveals the complicated three-dimensional morphologies, such as onion, helices and regular polyhedral structures.
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  • Koh Hashimoto, Takashi Ikegami
    Article type: General Physics
    Subject area: Mathematical methods in physics.
    2001 Volume 70 Issue 11 Pages 3221-3224
    Published: 2001
    Released on J-STAGE: February 28, 2003
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    Game dynamics with a mixed strategy player is studied. A new attracting set emerges under a certain condition by introducing a mixed strategy into a system with a pure strategies system. In terms of a replicator system, introducing a mixed strategy means to increase the number of rows and columns of the interaction matrix by 1 without changing its rank size. As a result, a system has a neutral dimension and a new attracting set emerges on the center manifold of a fixed point. A possible scenario of evolution via a mixed strategy is briefly discussed.
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  • Tetsuo Deguchi, Pijush K. Ghosh
    Article type: General Physics
    Subject area: Mathematical methods in physics.
    2001 Volume 70 Issue 11 Pages 3225-3237
    Published: 2001
    Released on J-STAGE: February 28, 2003
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    We construct and study a class of N particle supersymmetric Hamiltonians with nearest and next-nearest neighbor inverse-square interaction in one dimension. We show that inhomogeneous XY models in an external non-uniform magnetic field can be obtained from these super-Hamiltonians in a particular limit decoupling the fermionic degrees of freedom from the kinematic ones. We further consider a suitable deformation of these super-models such that inhomogeneous XXZ Hamiltonians in an external non-uniform magnetic field are obtained in the same limit. We show that this deformed Hamiltonian with rational potential is, (i) mapped to a set of free super-oscillators through a similarity transformation and (ii) supersymmetric in terms of a new, non-standard realization of the supercharge. We construct many exact eigenstates of this Hamiltonian and discuss about the applicability of this technique to other models.
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  • Seiji Miyashita, Keiji Saito
    Article type: General Physics
    Subject area: Mathematical methods in physics.
    2001 Volume 70 Issue 11 Pages 3238-3246
    Published: 2001
    Released on J-STAGE: February 28, 2003
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    At resonant tunneling points of nanoscale molecular magnets, a fluctuating random field causes successive Landau-Zener-Stückelberg transitions. We have studied dynamics of magnetization by a Langevin type Schrödinger equation and found that the successive transitions result in a stretched exponential decay with square-root time when the fluctuation of the field is regarded as an random walk, i.e., the Wiener process. When the fluctuation is bounded by a restoring force, i.e., the Ornstein-Uhlenbeck process, the relaxation obeys the exponential decay at the late stage, while it shows the stretched exponential decay at the early stage. The scaling relations of the relaxation functions at both stages are also studied as functions of the parameters: the strength of the fluctuation, the restoring force, and the energy gap of the system at the resonant point. Roles of the observed nonexponential decay are also discussed in various kinds of square-root time behavior found in experiments.
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  • Hidetsugu Sakaguchi
    Article type: General Physics
    Subject area: Mathematical methods in physics.
    2001 Volume 70 Issue 11 Pages 3247-3250
    Published: 2001
    Released on J-STAGE: February 28, 2003
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    A random multiplicative process with additive noise is described by a Langevin equation. We show that the fluctuation-dissipation relation is satisfied in the Langevin model, if the noise strength is not so strong.
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  • Zhi-Jie Tan, Xian-Wu Zou, Sheng-You Huang, Zhun-Zhi Jin
    Article type: General Physics
    Subject area: Mathematical methods in physics.
    2001 Volume 70 Issue 11 Pages 3251-3254
    Published: 2001
    Released on J-STAGE: February 28, 2003
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    Diffusion-limited aggregation (DLA) on nonuniform substrates was investigated by computer simulations. The nonuniform substrates are represented by Leath percolations with the occupied probability p. p stands for the degree of nonuniformity and takes values in the range pc ≤ p≤ 1, where pc is the threshold of percolation. The DLA cluster grows up on the Leath percolation substrate. The patterns of the DLA clusters appear asymmetrical and nonuniform, and the branches are relatively few for the case that p is close to pc. In addition, the pattern depends on the shape of substrate. As p increases from pc to 1, cluster changes to pure DLA gradually. Correspondingly, the fractal dimension increases from 1.46 to 1.68. Furthermore, the random walks on Leath percolations through the range pc ≤ p ≤ 1 were examined. Our simulations show the Honda-Toyoki-Matsushita relation is still reasonable for DLA growth in fractional dimensional spaces.
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  • Hokuto Iijima, Tachishige Hirose, Mitsuhiro Irako, Masatoshi Kajita, T ...
    Article type: General Physics
    Subject area: Mathematical methods in physics.
    2001 Volume 70 Issue 11 Pages 3255-3260
    Published: 2001
    Released on J-STAGE: February 28, 2003
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    On the basis of three dimensional (3-D) Monte Carlo simulation, we studied details of laser cooling (Doppler cooling) of ortho-Positronium (o-Ps) which would be applied to the achievement of Bose-Einstein condensation of positronium. The cooling is carried out by an ultraviolet laser with a wavelength of 243 nm being equivalent to the 1S-2P transition energy of o-Ps. For this purpose, we have constructed a laser cooling apparatus which consists of a slow positron generator and a long pulse, wide linewidth laser. A 3-D Monte Carlo calculation, which incorporated various parameters of laser beam and positronium distributions expected in the current laser cooling apparatus, revealed that 7% of o-Ps was able to be cool down to 1 K and to be confined in a relatively small volume without employing a special trap.
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  • Ali Maghari, Saeid Yeganegi
    Article type: General Physics
    Subject area: Mathematical methods in physics.
    2001 Volume 70 Issue 11 Pages 3261-3267
    Published: 2001
    Released on J-STAGE: February 28, 2003
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    Thermal diffusion factor and thermal conductivity of a binary isotopic fluid composed of H2 and D2 with a realistic intermolecular potential, namely Morse-Spline-Van der Waals (MSV), are computed at different densities and temperatures performing a newly developed non-equilibrium molecular dynamics algorithm. To achieve a deeper understanding of the thermal diffusion process at the molecular level, we investigate the effect of the shape interaction parameter of our model system on the thermal diffusion factor. We show that the thermal diffusion factor slightly increases with increasing the steepness of repulsive portion of the potential at low density, but strongly increases at high density. We also observe that the thermal conductivity is a weak function of the repulsive part of the potential at low density, but it depends strongly on the steepness of repulsive part of the potential at high-density.
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  • Katsuhiko Sato, Akihiko Toda
    Article type: General Physics
    Subject area: Mathematical methods in physics.
    2001 Volume 70 Issue 11 Pages 3268-3273
    Published: 2001
    Released on J-STAGE: February 28, 2003
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    The flow instability in a polymer liquid extruded from a die has been discussed on its temperature dependence, based on a modeling of the behavior by a statistical stick-slip model of a group of springs. The present experimental results of polyethylene melt showed the shift of an N-shaped flow curve to lower shear rate with decreasing temperature, which approaches the melting point of polyethylene crystals. This result is consistent with the microscopic modeling of the flow instability with the disentanglement of the chain in the bulk under high shear rate. The shift of flow curve with temperature explains the existence of the temperature window with minimum applied pressure under constant speed found by Keller et al.
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  • Kimitaka Itoh, Sanae-I. Itoh, Louis Giannone
    Article type: General Physics
    Subject area: Mathematical methods in physics.
    2001 Volume 70 Issue 11 Pages 3274-3284
    Published: 2001
    Released on J-STAGE: February 28, 2003
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    The physics of density limit phenomena in toroidal helical plasmas based on an analytic point model of toroidal plasmas is discussed. The combined mechanism of the transport and radiation loss of energy is analyzed, and the achievable density is derived. A scaling law of the density limit is discussed. The dependence of the critical density on the heating power, magnetic field, plasma size and safety factor in the case of L-mode energy confinement is explained. The dynamic evolution of the plasma energy and radiation loss is discussed. Assuming a simple model of density evolution, of a sudden loss of density if the temperature becomes lower than critical value, then a limit cycle oscillation is shown to occur. A condition that divides the limit cycle oscillation and the complete radiation collapse is discussed. This model seems to explain the density limit oscillation that has been observed on the Wendelstein 7-AS (W7-AS) stellarator.
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  • Mieko Toida, Akihiro Sugishima
    Article type: General Physics
    Subject area: Mathematical methods in physics.
    2001 Volume 70 Issue 11 Pages 3285-3290
    Published: 2001
    Released on J-STAGE: February 28, 2003
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    Current-driven instabilities and associated energy transport among different particle species in a plasma consisting electrons and hydrogen (H) and helium (He) ions are studied theoretically and numerically. First, a theory predicting the dominant unstable modes is developed. Theoretical estimates of energy gains of ions from the waves are also obtained. Next, by means of a three-dimensional electrostatic particle code with full ion and electron dynamics, the nonlinear evolution of the instabilities and the energy transfer to ions are further investigated. Simulations show that the second harmonic H cyclotron wave with parallel phase velocity equal to the initial electron drift speed eventually becomes dominant owing to the change in the electron velocity distribution function. The observed heating rate of He ions by the dominant wave is much greater than that of H ions. These simulation results are in good agreement with the theory.
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  • Kenji Ohoyama, Koji Kaneko, Kentaro Indoh, Hiroki Yamauchi, Aya Tobo, ...
    Article type: General Physics
    Subject area: Mathematical methods in physics.
    2001 Volume 70 Issue 11 Pages 3291-3295
    Published: 2001
    Released on J-STAGE: February 28, 2003
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    Detailed crystal structures of the tetragonal RB2C2 (R=La, Ce, Pr, Nd, Tb, Dy, Ho, Er, Tm and Lu) compounds which include the antiferroquadrupolar ordering materials, DyB2C2 and HoB2C2, have been investigated by neutron powder diffraction technique. RB2C2 are crystallised in the same LaB2C2 type crystal structure with P4/mbm symmetry. The structure of the B-C network which consists of non-regular squares and octagons are nearly the same in the system except slight rotation as rare earth atoms become heavier.
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  • Sheng Xu, Yutaka Moritomo, Kazuhiro Mori, Takashi Kamiyama, Tomohiko S ...
    Article type: General Physics
    Subject area: Mathematical methods in physics.
    2001 Volume 70 Issue 11 Pages 3296-3299
    Published: 2001
    Released on J-STAGE: February 28, 2003
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    Temperature dependence of the structural parameters is investigated in LaCoO3 that shows a spin state transition at Tspin ∼ 100 K by means of high-resolution time-of-fight (TOF) neutron powder diffraction measurements. We have found that the structural parameters, such as, Co-O bond length d and Co-O-Co bondangle Θ, show no detectable anomaly at Tspin. We have compared these structural features of LaCoO3 with those of the so-called spin-crossover complexes.
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  • Katsuhiko Hasebe, Syuhei Tsuchiya, Yukihiko Kawamura, Takanao Asahi
    Article type: General Physics
    Subject area: Mathematical methods in physics.
    2001 Volume 70 Issue 11 Pages 3300-3305
    Published: 2001
    Released on J-STAGE: February 28, 2003
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    The phase transition of betaine phosphite crystal associated with the ordering of PO3 radicals at phase I to II transition has been studied by X-ray scattering: The observations are concerned on (1) the temperature dependence of lattice constants, (2) the temperature dependence of the order parameter of PO3 which followed the relation η ∝ (Tc-T)β, β=0.33(1), and (3) the anisotropic distribution of critical diffuse scattering in the reciprocal space above Tc; elongated along the c-direction, shortened along the b*-direction. The critical X-ray diffuse scattering has been analyzed on an Ising model to obtain effective interaction between PO3 ions. The results are summarized as follows. (1) The correlation lengths along three principal directions of anisotropic scattering distribution was estimated. (2) The temperature dependence of the correlation length follows nearly the mean-field behavior, ξ ∝ (T-Tc), ν=0.5.
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  • Kanwar J. Singh, Yoshimi Tsuchiya
    Article type: General Physics
    Subject area: Mathematical methods in physics.
    2001 Volume 70 Issue 11 Pages 3306-3311
    Published: 2001
    Released on J-STAGE: February 28, 2003
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    Sound velocity and density measurements have been carried out in the liquid Ga-Te system as a function of temperature and composition. Results obtained have been used to deduce the compressibility, molar volume and thermal expansion coefficient with respect to the variation of temperature and composition. Two-melt region in the Ga rich region has been determined. Critical behavior of sound velocity has been observed in the two-melt region. Discussion has been carried out in terms of the structural change of Ga2Te3 association and the concentration fluctuations induced by the structural change in the melt.
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  • Takashi Imamura, Kazuhiro Hikami
    Article type: General Physics
    Subject area: Mathematical methods in physics.
    2001 Volume 70 Issue 11 Pages 3312-3321
    Published: 2001
    Released on J-STAGE: February 28, 2003
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    For the quantum wires which belong to the Bogoliubov-de Gennes universality class, the averages and variances of the conductance and shot-noise power are calculated by the method of the moment expansion based on the DMPK equation. We discuss the universal behaviors of the transport properties.
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  • Tatsuo Kanashiro, Rahman Md. Mahbubar, Yoshitaka Michihiro, Koichi Nak ...
    Article type: General Physics
    Subject area: Mathematical methods in physics.
    2001 Volume 70 Issue 11 Pages 3322-3325
    Published: 2001
    Released on J-STAGE: February 28, 2003
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    The temperature dependence of nuclear relaxation rate, 1/T1 has been measured for copper halides, CuX with X being Cl, Br and I. The results are interpreted in terms of the quadrupole relaxation due to lattice vibrations and defect motions. The data of 1/T1 are compared with a model calculation based on an ionic model, in which the degree of covalent bonding λ0 is estimated to be 63% for CuCl, 49% for CuBr and 27% for CuI. The λ0 values for copper halides are compared with previous values for silver and sodium halides, and also compared with the ionicity of ANB8-N binary compounds. The relation between λ0 values and migration energies Em for cation vacancies derived from 1/T1 data is discussed in connection with the superionicity of α-AgI.
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  • Yoshihumi Tokiwa, Dai Aoki, Yoshinori Haga, Etuji Yamamoto, Shugo Iked ...
    Article type: General Physics
    Subject area: Mathematical methods in physics.
    2001 Volume 70 Issue 11 Pages 3326-3330
    Published: 2001
    Released on J-STAGE: February 28, 2003
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    We succeeded in growing a high-quality single crystal of UIn3 by the self-flux method and measured the electrical resistivity, magnetic susceptibility, magnetization, specific heat and de Haas-van Alphen (dHvA) oscillation. We confirmed the Néel temperature at TN=88 K from both the electrical resistivity and magnetic susceptibility measurements. We observed many dHvA branches. The Fermi surfaces are found to consist of closed Fermi surfaces and a multiply-connected Fermi surface. The cyclotron mass is relatively large, ranging from 9.8 to 33 m0.
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  • Kousuke Yakubo
    Article type: General Physics
    Subject area: Mathematical methods in physics.
    2001 Volume 70 Issue 11 Pages 3331-3341
    Published: 2001
    Released on J-STAGE: February 28, 2003
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    A transfer-matrix method is found to be an efficient numerical technique to study quantum transport of two-dimensional (2D) electron systems subject to long-range inhomogeneous magnetic fields. In contrast to conventional transfer-matrix techniques for 2D transport, the method developed in this paper does not require any diagonalization procedure. It is, therefore, possible to calculate the conductance and the current distribution within the same order of a computing time with that of a one-dimensional transfer-matrix calculation. Applying this method to several 2D electron systems in inhomogeneous magnetic fields, we demonstrate the efficiency of this method.
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  • Yoshioki Isobe, Naoki Miyajima, Guang Ri Wu, Hiroshi Negishi, Minoru S ...
    Article type: General Physics
    Subject area: Mathematical methods in physics.
    2001 Volume 70 Issue 11 Pages 3342-3347
    Published: 2001
    Released on J-STAGE: February 28, 2003
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    Long-length scale interaction model proposed by Littlewood has been extended to study dipole and screening effects on sliding motion of one-dimensional charge-density-wave (CDW). The system in the extended model consists of a site-by-site main-system fixed at pinning centers and the continuous sub-systems in each pinning site. For strong pinning case, we have demonstrated these effects on the CDW phase, CDW current, and narrow band noise spectrum. The dipole effect suppresses the pinning potential and gives rise to a change from deformable “plastic flow” like to rigid “moving solid” like CDW condenstates, while the screening effect acts to recover the former.
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  • F. L. Shyu, Ming Fa Lin, C. P. Chang, R. B. Chen, J. S. Shyu, Y. C. Wa ...
    Article type: General Physics
    Subject area: Mathematical methods in physics.
    2001 Volume 70 Issue 11 Pages 3348-3355
    Published: 2001
    Released on J-STAGE: February 28, 2003
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    Electronic properties of AB-stacked nanographite ribbons depend on the edge structure, the ribbon width (Ny), and the ribbon number (Nz). All zigzag ribbons are metals, while armchair ribbons are metals only for Ny=3I+2 (I an integer). The dependence of energy gap on the ribbon number is weak for the semiconducting armchair multiribbons with Nz>5. The semiconductor-metal transition is absent in the increasing of Nz. Density of states exhibits many special structures. The interlayer interactions would affect the energy dispersions of band structures. They could induce the hybridization of energy bands, the new partial flat bands along the kx- or kz-direction, the asymmetry of the electronic structure about the Fermi level, the change from the direct energy gap into the indirect energy gap, the destruction of the state degeneracy, and the alternation of the special structures in the density of states.
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  • Zhong Fang, Kiyoyuki Terakura
    Article type: General Physics
    Subject area: Mathematical methods in physics.
    2001 Volume 70 Issue 11 Pages 3356-3361
    Published: 2001
    Released on J-STAGE: February 28, 2003
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    To gain insights into the fundamental and characteristic features of the surface of doped manganites, we constructed a general magnetic phase diagram of La1-xSrxMnO3 (001) surfaces in the plane spanned by x and the bulk tetragonal distortion c/a, from the first-principles calculations. We found that the surfaces are quite different from the bulk in the sense that both the (La,Sr)O and MnO2 terminated surfaces show strong tendency toward antiferromagnetism (A-type and C-type respectively). The basic physics governing the phase diagram can be understood in terms of surface effective doping and surface orbital polarization. It is also found that the strong surface segregation of Sr atoms is mostly caused by the electrostatic interaction and will further enhance the tendency toward surface antiferromagnetism.
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  • Takaki Muramatsu, Naoyuki Tateiwa, Tatsuo C. Kobayashi, Katsuya Shimiz ...
    Article type: General Physics
    Subject area: Mathematical methods in physics.
    2001 Volume 70 Issue 11 Pages 3362-3367
    Published: 2001
    Released on J-STAGE: February 28, 2003
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    The pressure dependence of transport properties in CeRhIn5 was studied up to 8.5 GPa by using a diamond-anvil cell. The electrical resistivity does not follow the T2-dependecne of a Fermi liquid nature under any pressure. In this non-Fermi liquid state, superconductivity was observed in a wide pressure range of 1.5 GPa<P<7.6 GPa. The superconducting temperature TC has a double-maximum structure with a minimum at 5.2 GPa. A maximum of TC=2.2 K was observed at P=2.5 GPa, where the corresponding electrical resistivity just above TC has the maximum. The upper critical field HC2 and the magnetoresistances were also investigated under pressure.
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  • Yusuke Kato, Nobuhiko Hayashi
    Article type: General Physics
    Subject area: Mathematical methods in physics.
    2001 Volume 70 Issue 11 Pages 3368-3376
    Published: 2001
    Released on J-STAGE: February 28, 2003
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    The pair-potential and current density around a single vortex of the two-dimensional chiral p-wave superconductor with d=ˆz(px ± i py) are determined self-consistently within the quasiclassical theory of superconductivity. Shrinking of the vortex core at low temperatures are considered numerically and analytically. Temperature-dependences of the spatial variation of pair-potential and circular current around the core and density of states at zero energy are the same as those in the isotropic s-wave case. When the senses of vorticity and chirality are opposite, however, we find two novel results; 1) the scattering rate due to non-magnetic impurities is considerably suppressed, compared to that in the s-wave vortex. From this observation, we expect that the chiral p-wave superconductors provide the best chance to observe the shrinking of the vortex (“Kramer—Pesch effect”) experimentally. 2) The pair-potential of chiral p-wave superconductors inside vortex core recovers a combined time-reversal-Gauge symmetry, although this symmetry is broken in the region far from the vortex core. This local recovery of symmetry leads to the suppression of the impurity effect inside vortex core.
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  • Zenji Hiroi, Masafumi Hanawa, Naoya Kobayashi, Minoru Nohara, Hidenori ...
    Article type: General Physics
    Subject area: Mathematical methods in physics.
    2001 Volume 70 Issue 11 Pages 3377-3384
    Published: 2001
    Released on J-STAGE: February 28, 2003
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    A novel cuprate Volborthite, Cu3V2O7(OH)2·2H2O, containing an S-1/2 (Cu2+ spin) kagomé-like lattice is studied by magnetic susceptibility, specific heat, and 51V NMR measurements. Signs for neither long-range order nor spin-gapped singlet ground states are detected down to 1.8 K, in spite of large antiferromagnetic couplings of ∼100 K between Cu spins forming a two-dimensional kagomé-like network. It is suggested that Volborthite represents a system close to a quantum critical point between classical long-range ordered and quantum disordered phases.
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  • Keiji Saito, Seiji Miyashita
    Article type: General Physics
    Subject area: Mathematical methods in physics.
    2001 Volume 70 Issue 11 Pages 3385-3390
    Published: 2001
    Released on J-STAGE: February 28, 2003
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    The magnetization process as a response to a sweeping magnetic field in the thermal environment is investigated by using the quantum master equation. In a slow sweeping velocity region where the system shows quasi-adiabatic motion, a magnetic plateau in the magnetization process has been observed in the recent experiment of V15 [Phys. Rev. Lett. 84 (2000) 3454]. Although the experiment was explained from a view of small capacity of the phonon heat bath, i.e., the phonon bottleneck effect, we found that a magnetic plateau appears almost regardless of the properties of the heat bath in the quasi-adiabatic transition and the appearance of the plateau is quite universal. We call it `Magnetic Foehn effect'. On the other hand, the magnetic plateau also appears in a fast sweeping velocity region by the Landau-Zener-Stückelberg mechanism which is different from the above mechanism in a slow sweeping region, and we study the crossover between them. We also propose an experiment which clarifies the structure of coupling to the thermal reservoir.
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  • Kanji Takehana, Tadashi Takamasu, Masashi Hase, Giyuu Kido, Kunimitsu ...
    Article type: General Physics
    Subject area: Mathematical methods in physics.
    2001 Volume 70 Issue 11 Pages 3391-3397
    Published: 2001
    Released on J-STAGE: February 28, 2003
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    The folded phonon mode at 98 cm-1 on CuGeO3, which was found in our previous study, was determined to be strongly coupled to the spin system. The splitting of the folded phonon mode was formulated to be caused by the interaction between the spin-phonon coupled modes at k=±(qSP - Δq) through the modulation of the spin polarization with periodicity of 2Δq in the incommensurate (IC) phase. This mode can successfully explain the behavior of the 98 cm-1 folded phonon mode in the IC phase. We have also formulated the reason why the intensity of the folded modes in general decreases in the IC phase.
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  • Shigeki Onoda, Masatoshi Imada
    Article type: General Physics
    Subject area: Mathematical methods in physics.
    2001 Volume 70 Issue 11 Pages 3398-3418
    Published: 2001
    Released on J-STAGE: February 28, 2003
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    Thermodynamic and dynamical properties of filling-control metal-insulator transition (MIT) in the Hubbard model are studied by the operator projection method, especially in two dimensions. This is a non-perturbative analytic approach to many-body systems. The present theory incorporates the Mott-Hubbard, Brinkman-Rice and Slater pictures of the MIT into a unified framework, together with reproducing low-energy narrow band arising from spin-charge fluctuations. At half filling, single-particle spectra A(ω, k) show formation of two Hubbard bands and their antiferromagnetic shadows separated by a Mott gap in the plane of energy ω and momentum k with lowering temperatures. These four bands produce splitting to two low-energy narrow bands and two SDW-like bands in the dispersion. Near half filling, the low-energy narrow band persists at low temperatures. This narrow band has a particularly weak dispersion and large weights around (π, 0) and (0, π) momenta. The velocity of these low-energy excitations is shown to vanish towards the MIT, indicating the mass divergence as in the Brinkman-Rice picture, but most prominently around (π,0) and (0,π) with strong momentum dependence. This reflects the suppression of the coherence near the MIT. Main structures in A(ω, k) show remarkable similarities to quantum Monte-Carlo results in two dimensions as well as in the one-dimensional Hubbard model. The charge compressibility appears to diverge with decreasing doping concentration in both one and two dimensions in agreement with the exact and quantum Monte-Carlo results. We also discuss implications of the flat dispersion formed near the Fermi level to the observations in high-Tc cuprate superconductors.
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  • Jin Soo Kim, Tae Kwon Song
    Article type: General Physics
    Subject area: Mathematical methods in physics.
    2001 Volume 70 Issue 11 Pages 3419-3423
    Published: 2001
    Released on J-STAGE: February 28, 2003
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    The modulus spectroscopy of potassium lithium niobate (KLN) crystals was investigated in the frequency range from 100 Hz to 10 MHz and temperature range from 30°C to 600°C. The dielectric anomaly with a broad peak was observed around 430°C. The ac conductivity is frequency dependent at low temperatures such as σ=σdc+Aωs, and shows a frequency independent at low frequencies and high temperatures. The electrical relaxation in ionically conducting KLN crystal analysed in terms of modulus formalism. The electric modulus which describes the dielectric relaxation behavior is fitted to the Kohlrausch-Williams-Watts (KWW) exponential function. Near the phase transition temperature, a stretched exponential parameter β indicating the degree of distribution of the relaxation time has a small value. The activation energy near the phase transition temperature is different from that of above and below phase transition temperature. The temperature dependence of the electric modulus is studied and the results are discussed.
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  • Akimasa Ohnishi, Ken-ichi Tanaka, Mamoru Kitaura, Takafumi Otomo, Take ...
    Article type: General Physics
    Subject area: Mathematical methods in physics.
    2001 Volume 70 Issue 11 Pages 3424-3427
    Published: 2001
    Released on J-STAGE: February 28, 2003
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    Reflection spectra of (C2H5NH3)2CdCl4 single crystals have been investigated in the range of 3-30 eV using synchrotron radiation. Two kinds of exciton bands with the splitting of the order of 0.1 eV, which is almost equal to the spin-orbit splitting of a Cl atom, are observed at 6.19 and 8.20 eV at 7 K. These bands are located at the energy positions close to the lowest exciton bands of CdCl2 and C2H5NH3Cl crystals, respectively. On rising the sample temperatures, the 8.20 eV band shows a discontinuous peak-shift of 0.1 eV around the temperature where a structural phase transition occurs, while such a result is not observed for the 6.19 eV band. The 6.19 eV band is assigned to the electronic transition from the Cl- 3p valence band to the lower Cd2+ 5s conduction band, and the 8.20 eV band to that from the Cl- 3p valence band to the upper NH3- s-like conduction band.
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  • Kiwang Jang, I. G. Kim, H. J. Seo, B. K. Moon, H. S. Bae, B. Y. Yu, J. ...
    Article type: General Physics
    Subject area: Mathematical methods in physics.
    2001 Volume 70 Issue 11 Pages 3428-3431
    Published: 2001
    Released on J-STAGE: February 28, 2003
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    A Sm2+-containing Mg0.5Sr0.5FCl0.5Br0.5 mixed crystal was synthesized by firing at 1,100°C 2 hours in a reducing stream of hydrogen gas and examined with an X-ray diffractometer for the crystalline structure. We measured the optical properties of Sm2+-ion and observed the efficiencies of persistent spectral hole burning depend on hole burning methods at 90 K and 300 K. At 90 K, PSHB was made much more efficiently by using the photon-gated (two color) spectral hole burning process compared to the one color hole burning process, while the one color hole burning process is much more efficient at 300 K.
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  • Shunji Nojima
    Article type: General Physics
    Subject area: Mathematical methods in physics.
    2001 Volume 70 Issue 11 Pages 3432-3445
    Published: 2001
    Released on J-STAGE: February 28, 2003
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    The polariton-mediated photonic crystal laser is theoretically investigated, which is made of a periodic structure containing excitonic and gain materials in its unit cell—this kind of structure can also be called a polaritonic crystal. The basic concept of this laser lies in exploiting the anomalous dispersion of the polaritonic crystal as the photonic environment in which light created by stimulated emission propagates. This crystal provides a stage for photons, which enables a significant enhancement of optical gain in the vicinity of its band edge. The gain enhancement is found to be caused by the increased confinement of light in the gain region and the slowing-down of light in the presence of excitons. This effect permits the laser to oscillate with a very low threshold and in the single mode. The threshold-gain values obtained are found to be much lower than those for the Fabry-Perot lasers and the Distributed-Feedback lasers. Moreover, exciton damping, which is undesirable for laser action, is shown to be decreased to a considerable degree by designing the polaritonic crystal structure appropriately. All these advantages of polaritonic crystals stem from the fact that the radiation field is modulated significantly by adding excitons to conventional photonic crystals.
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  • Minoru Itoh, Masao Kamada
    Article type: General Physics
    Subject area: Mathematical methods in physics.
    2001 Volume 70 Issue 11 Pages 3446-3451
    Published: 2001
    Released on J-STAGE: February 28, 2003
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    The line shape of Auger-free luminescence (AFL), caused by radiative recombination of holes in the outermost-core band with valence electrons, has been studied for CsCl, CsBr and BaF2 in comparison to photoelectron spectra of the valence bands. It is confirmed that the main part of AFL locates on the low-energy side of the valence-band region estimated from the maximum of the outermost-core band in the photoelectron spectra. Furthermore, its low-energy tail extends by approximately 0.5-1.0 eV below the minimum of the valence band. These results clearly indicate that the core hole induces considerable lattice distortion around itself, which is kept well during the radiative transition. The line shape of AFL is favorably explained in terms of an energy-band picture in which the lattice relaxation is taken into account in principle.
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  • Akira Sakai, Masaaki Negishi, Eiji Fujiwara, Chikako Moriyoshi, Kazuyu ...
    Article type: General Physics
    Subject area: Mathematical methods in physics.
    2001 Volume 70 Issue 11 Pages 3452-3456
    Published: 2001
    Released on J-STAGE: February 28, 2003
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    Raman spectra of the langbeinite-type crystals K2Mn2(SO4)3 and (NH4)2Cd2(SO4)3 have been observed by using a micro-Raman scattering technique with a special attention to internal modes of SO4 molecules. The observed peaks are well assigned to the internal modes of SO4 in both the high- and low-temperature phases. At the phase transition temperature, new internal modes appear owing to the inequivalence of the molecular sites in the crystal. In addition, micro-Raman spectra have been observed at several positions on the surface of a single crystal. Micro-Raman spectra just at the transition temperature show either the high-temperature structure or the low-temperature structure as a function of the observed position. It is concluded that the sample single-crystal consists of the local regions which have different transition temperatures. This result indicates that not the intermediate phase but the coexistence of two phases appears in these langbeinite-type crystals.
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  • Keiji Fukui, Haruhiko Ogasawara, Akio Kotani, Toshiaki Iwazumi, Hirono ...
    Article type: General Physics
    Subject area: Mathematical methods in physics.
    2001 Volume 70 Issue 11 Pages 3457-3463
    Published: 2001
    Released on J-STAGE: February 28, 2003
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    Theoretical calculations and experimental measurements are performed for magnetic circular dichroism in resonant X-ray emission spectroscopy (MCD-RXES) in Gd3+ systems. It is shown that when the incident X-ray direction is perpendicular to the magnetization of the sample the MCD-RXES originates from the quantum mechanical interference which is characteristic of the coherent second order optical process, while when it is parallel to the magnetization the second order optical process reduces to the so-called two-step process with vanishing interference effect. The behavior of MCD-RXES calculated for the 2p → 5d electric dipole excitation and 3d → 2p dipole radiative decay in Gd3+ is in good agreement with that measured experimentally for a Gd33Co67 amorphous alloy. The effects of the 2p → 4f electric quadrupole excitation and the 2p → ε d electric dipole excitation are also studied.
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  • Yutaka Uekusa, Akihide Oguchi
    Article type: General Physics
    Subject area: Mathematical methods in physics.
    2001 Volume 70 Issue 11 Pages 3464-3465
    Published: 2001
    Released on J-STAGE: February 28, 2003
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  • Xiao Jun Liu, Yutaka Moritomo, Arao Nakamura, Hidekazu Tanaka, Tomoji ...
    Article type: General Physics
    Subject area: Mathematical methods in physics.
    2001 Volume 70 Issue 11 Pages 3466-3467
    Published: 2001
    Released on J-STAGE: February 28, 2003
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  • Katsuhiko Takegahara, Hisatomo Harima, Akira Yanase
    Article type: General Physics
    Subject area: Mathematical methods in physics.
    2001 Volume 70 Issue 11 Pages 3468
    Published: 2001
    Released on J-STAGE: February 28, 2003
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  • Kenji Suzuki, Yasuo Yamaguchi, Takejiro Kaneko, Hajime Yoshida, Yoshih ...
    Article type: General Physics
    Subject area: Mathematical methods in physics.
    2001 Volume 70 Issue 11 Pages 3469
    Published: 2001
    Released on J-STAGE: February 28, 2003
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