Journal of the Physical Society of Japan
Online ISSN : 1347-4073
Print ISSN : 0031-9015
ISSN-L : 0031-9015
Volume 69, Issue 12
Displaying 1-50 of 52 articles from this issue
  • Hiroshi Matsui, Yoshiyuki Yoshida, Atsushi Mukai, Rikio Settai, Yoshic ...
    Article type: General Physics
    Subject area: Mathematical methods in physics.
    2000 Volume 69 Issue 12 Pages 3769-3772
    Published: 2000
    Released on J-STAGE: April 25, 2003
    JOURNAL RESTRICTED ACCESS
    The acoustic de Haas-van Alphen (dHvA) effect and temperature dependence of the transverse mode (C11-C12)/2 have been measured in a layered Perovskite superconductor Sr2RuO4 with Tc* = 1.42 K. From the acoustic dHvA oscillations for α and β orbits along [001], the area coefficients are estimated to be |ΛB1gα| = 0.8 and |ΛB1gβ| = 0.2 ∼ 0.3. Both Fermi surfaces consisting of hybridized Ru-4dzx(yz) orbitals couple weakly to εxxyy, because the in-plane shear strain hardly varies the spacing between the alternating RuO2 layers. Large softening occurs below 220 K, which corresponds to the rotational instability. The rotational deformation of the RuO6 octahedron is induced perturbingly by εxxyy which reduces the lattice matching.
    Download PDF (154K)
  • Takeo Hoshi, Takeo Fujiwara
    Article type: General Physics
    Subject area: Mathematical methods in physics.
    2000 Volume 69 Issue 12 Pages 3773-3776
    Published: 2000
    Released on J-STAGE: April 25, 2003
    JOURNAL RESTRICTED ACCESS
    From the order-N electronic-structure formulation, a Hamiltonian is derived, of which the lowest eigen state is the generalized or composite-band Wannier state. This Hamiltonian maps the locality of the Wannier state to that of a virtual impurity state and to a perturbation from a bonding orbital. These theories are demonstrated in the diamond-structure solids, where the Wannier states are constructed by a practical order-N algorithm with the Hamiltonian. The results give a prototypical picture of the Wannier states in covalent-bonded systems.
    Download PDF (139K)
  • Shunsuke Yoshii, Satoshi Iikubo, Taketomo Kageyama, Keisuke Oda, Yasuy ...
    Article type: General Physics
    Subject area: Mathematical methods in physics.
    2000 Volume 69 Issue 12 Pages 3777-3780
    Published: 2000
    Released on J-STAGE: April 25, 2003
    JOURNAL RESTRICTED ACCESS
    Hall resistivity ρH has been investigated for single crystals of pyrochlore molybdate Nd2Mo2O7. With decreasing temperature T, the anomalous Hall effect appears at around the Curie temperature TC (∼95 K). In the relatively high temperature region (T > 60 K), ρH can be described by the well-known equation ρH=R0H+4 π RsM, where R0 and Rs are the ordinary and anomalous Hall coefficients, respectively, and M is the net magnetization predominantly contributed by the Mo spins. With further decreasing T, the ordering of the Nd moments, which is confirmed by neutron diffraction studies carried out by the present authors' group, induces marked change in the behavior of the anomalous part of ρH. The behavior in the low temperature region has been found to be simply described by the equation ρH=R0H+4 π RsMMo+4π Rs'MNd, where MMo and MNd are the net magnetizations of the Mo- and Nd-moments, respectively. This result and the T-dependence of Rs and Rs' are quite different from those known for ordinary ferromagnets and might be related to the nonzero spin chirality observed in the present system.
    Download PDF (193K)
  • Feng-Lin Shyu, Ming-Fa Lin
    Article type: General Physics
    Subject area: Mathematical methods in physics.
    2000 Volume 69 Issue 12 Pages 3781-3784
    Published: 2000
    Released on J-STAGE: April 25, 2003
    JOURNAL RESTRICTED ACCESS
    The weak interlayer bonding in Bernal graphite induces low-density free carriers and thus low-frequency plasmons (<0.2 eV). Such plasmons reveal themselves as pronounced peaks in the loss spectra and abrupt edge structures in the reflectance spectra. The low-frequency plasmons are very sensitive to changes in temperature and momentum, mainly owing to the unique low-energy band structure. They can exist at larger momenta as temperature increases. The plasmon frequency clearly increases with temperature and momentum. The plasmon peak is broadened by temperature; furthermore, it decreases with momentum. The calculated results are consistent with the experimental measurements.
    Download PDF (159K)
  • Yukitoshi Motome, Nobuo Furukawa
    Article type: General Physics
    Subject area: Mathematical methods in physics.
    2000 Volume 69 Issue 12 Pages 3785-3788
    Published: 2000
    Released on J-STAGE: April 25, 2003
    JOURNAL RESTRICTED ACCESS
    Ferromagnetic transition in three-dimensional double-exchange models is studied by the Monte Carlo method. Critical temperature Tc is precisely determined by finite-size scaling analysis. Strong spin fluctuations in this itinerant system significantly reduce Tc from mean-field estimates. By choosing appropriate parameters, obtained values of Tc quantitatively agree with experiments for the ferromagnetic metal regime of (La,Sr)MnO3, which is a typical perovskite manganite showing colossal magnetoresistance. This indicates that the double-exchange mechanism alone is sufficient to explain Tc in this material. Critical exponents are also discussed.
    Download PDF (163K)
  • Satoru Kunii
    Article type: General Physics
    Subject area: Mathematical methods in physics.
    2000 Volume 69 Issue 12 Pages 3789-3791
    Published: 2000
    Released on J-STAGE: April 25, 2003
    JOURNAL RESTRICTED ACCESS
    In Ca1-xLaxB6 (x=0.005) single crystals using 9.6 GHz microwave frequency at room temperature, we observed resonance lines which exhibit sample-shape dependence with respect to their resonance field, linewidth and numbers. A disk-shaped sample showed a single, symmetrical resonance line and a large lower-field shift. The resonance field of the disk sample was investigated in detail and exhibits cos -1 θ dependence, where θ is the angle between the disk plane and the external magnetic field. This finding leads to the conclusion that the spins are strongly forced to stay in the disk plane by an anisotropy field. The symmetrical resonance line originates from surface spins within the microwave skin depth in a metallic sample. At a higher angle θ, the resonance line became antisymmetrical. At the microwave frequency of 24 GHz, the resonance line shape was also antisymmetrical even at θ=0. We conclude that spins in Ca0.995La0.005B6 exist only within the surface layer of approximately 1.5 μm thick, and they feel strong surface magnetic anisotropy of an easy plane type.
    Download PDF (125K)
  • Hiroshi Noguchi, Masako Takasu
    Article type: General Physics
    Subject area: Mathematical methods in physics.
    2000 Volume 69 Issue 12 Pages 3792-3795
    Published: 2000
    Released on J-STAGE: April 25, 2003
    JOURNAL RESTRICTED ACCESS
    We studied the electrophoretic behavior of DNA chains in linear-polymer solutions using Brownian dynamics with an anisotropic friction tensor. We simulated the linear-shaped motion of DNA observed in highly entangled solutions [Ueda et al.: Biophys. Chem. 71 (1998) 113] using a model with a chain segment equal to 1/4 of the persistence length. A linear conformation is seen for a chain with high segment-density regions, which remain at the same positions in space, with a high anisotropy of friction, while a U-shaped conformation is seen for a chain with a low anisotropy of friction.
    Download PDF (146K)
  • Heng Fan, Miki Wadati
    Article type: General Physics
    Subject area: Mathematical methods in physics.
    2000 Volume 69 Issue 12 Pages 3797-3804
    Published: 2000
    Released on J-STAGE: April 25, 2003
    JOURNAL RESTRICTED ACCESS
    We apply the nested algebraic Bethe ansatz method to solve the eigenvalue problem for the SU(4) extension of the Hubbard model. The Hamiltonian is equivalent to the SU(4) graded permutation operator. The graded Yang-Baxter equation and the graded Quantum Inverse Scattering Method are used to obtain the eigenvalue of the SU(4) extension of the Hubbard model.
    Download PDF (149K)
  • Shinji Koga
    Article type: General Physics
    Subject area: Mathematical methods in physics.
    2000 Volume 69 Issue 12 Pages 3805-3829
    Published: 2000
    Released on J-STAGE: April 25, 2003
    JOURNAL RESTRICTED ACCESS
    We find in general two canonically conjugate variables describing an area-preserving 2D mapping defined on a curved Poincaré section in 2D Hamiltonian dynamical systems. In the first part we find that derivation of canonical coordinates is based upon time-invariants retaining memory of initial conditions. In the next part we discuss a linear stability of a periodic trajectory defined as a fixed point on a curved surface, comparing with a Floquet theory. In the third part under an ergodicity hypothesis we discuss a relation of canonical coordinates to statistical averages on a micro-canonical ensemble for variables defined on a curved surface. A representative statistical average is a micro-canonical of an elapsed time between two consecutive crossings, defined by a ratio of two densities of states. We consider as a concrete example a Hénon-Heiles Hamiltonian.
    Download PDF (378K)
  • Kenichi Sasaki, Masahiro Hotta
    Article type: General Physics
    Subject area: Mathematical methods in physics.
    2000 Volume 69 Issue 12 Pages 3830-3839
    Published: 2000
    Released on J-STAGE: April 25, 2003
    JOURNAL RESTRICTED ACCESS
    An attempt is made to construct composable composite entropy with different q indices of subsystems and address the H-theorem problem of the composite system. Though the H-theorem does not hold in general situations, it is shown that some composite entropies do not decrease in time in near-equilibrium states and factorized states with negligibly weak interaction between the subsystems.
    Download PDF (167K)
  • Toshiki Tajima, Kazuhiko Soyama, James Koga, Hiroshi Takuma
    Article type: General Physics
    Subject area: Mathematical methods in physics.
    2000 Volume 69 Issue 12 Pages 3840-3846
    Published: 2000
    Released on J-STAGE: April 25, 2003
    JOURNAL RESTRICTED ACCESS
    We introduce the process of nonresonant laser interaction with neutrons. A sufficiently strong laser beam can couple with the magnetic dipole of neutrons. The mean force of appropriately arranged laser beams causes specific momentum kicks through the beat of lasers at specific spatio-temporal positions. Such a kick corresponds to the neutron interaction with photons in the extreme low energy regime. We also suggest a possible method to detect a phase shift of the wave functions of neutrons of energy 3×10-3 eV with and without photon interaction by neutron interferometry, so that an effective neutron measurement of the laser kick is realized. The present ultra-sensitive neutron measurement with lasers introduces a new probe of neutrons in the extreme low energy regime.
    Download PDF (193K)
  • Yukio Kaneda
    Article type: General Physics
    Subject area: Mathematical methods in physics.
    2000 Volume 69 Issue 12 Pages 3847-3852
    Published: 2000
    Released on J-STAGE: April 25, 2003
    JOURNAL RESTRICTED ACCESS
    An approximation for single-particle diffusion in strongly stratified and/or rapidly rotating turbulence is derived on the basis of a linearized approximation of the equations of motion as well as Corrsin's conjecture for the Lagrangian two-time correlation. The approximation suggests that single-particle diffusion may be strongly suppressed by stratification and rotation of turbulence. It also suggests that the effect of slow rotation in strongly stratified turbulence nor that of weak stratification in rapidly rotating turbulence is not simply additive, and that the degree of suppression of turbulent diffusion depends not only on single-point statistics such as the total kinetic energy, but also on two-point statistics or the spectra of the initial velocity and density fields.
    Download PDF (126K)
  • Naohiro Koshiji, Hiroyuki Mashiyama
    Article type: General Physics
    Subject area: Mathematical methods in physics.
    2000 Volume 69 Issue 12 Pages 3853-3859
    Published: 2000
    Released on J-STAGE: April 25, 2003
    JOURNAL RESTRICTED ACCESS
    The crystal structure of the normal phase in {N(CH3)4}2MnCl4 has been analyzed for two models: a displacive model and a disordered model. In the former model, the constituent tetrahedra of tetramethylammonium and tetrachloromanganate satisfy a mirror symmetry themselves imposed by the crystal symmetry. In the latter model, each tetrahedron occupies two equivalent positions related by the mirror symmetry with an equal occupation probability: split atom method. A special attention has been paid to their thermal parameters; the former model exhibits an abnormal increase of the parameters near the transition temperature indicating a critical phenomenon. From the significant test for the R factor, the latter model seems to be more adequate than the former one. The disorderness of tetrahedra of tetramethylammonium is also confirmed by double peaks in Fourier synthesis map. On the other hand, MnCl4 can be well represented both by the displacive and the disordered models.
    Download PDF (224K)
  • Kazuhisa Ohmura, Namiko Aoki, Takashi Nakayama
    Article type: General Physics
    Subject area: Mathematical methods in physics.
    2000 Volume 69 Issue 12 Pages 3860-3863
    Published: 2000
    Released on J-STAGE: April 25, 2003
    JOURNAL RESTRICTED ACCESS
    Polarized Raman spectra of ordered-vacancy Ga2Se3 were calculated using the sp3s* tight-binding and vibration models. We found a large peak around 150 cm-1 which originates from the breathing-like movement of Se atoms around the vacancy. Reflecting the localized nature of vibration and the dangling-bond direction of three-coordinated Se atoms, this peak shows large intensity and anisotropy; the intensity is large for the light polarization perpendicular to the vacancy array, in contrast to the anisotropy observed in the photo-absorption and luminescence. These results well explain the experiments.
    Download PDF (193K)
  • Tomoya Isoshima, Tetsuo Ohmi, Kazushige Machida
    Article type: General Physics
    Subject area: Mathematical methods in physics.
    2000 Volume 69 Issue 12 Pages 3864-3869
    Published: 2000
    Released on J-STAGE: April 25, 2003
    JOURNAL RESTRICTED ACCESS
    It is investigated theoretically that magnetized Bose-Einstein condensation (BEC) with the internal (spin) degrees of freedom exhibits a rich variety of phase transitions, depending on the sign of the interaction in the spin channel. In the antiferromagnetic interaction case there exist always double BEC transitions from single component BEC to multiple component BEC. In the ferromagnetic case BEC becomes always unstable at a lower temperature, leading to a phase separation. The detailed phase diagram for the temperature vs the polarization, the spatial spin structure, the distribution of non-condensates and the excitation spectrum are examined for the harmonically trapped systems.
    Download PDF (169K)
  • Yoshihiro Ishibashi, Ted Janssen
    Article type: General Physics
    Subject area: Mathematical methods in physics.
    2000 Volume 69 Issue 12 Pages 3870-3872
    Published: 2000
    Released on J-STAGE: April 25, 2003
    JOURNAL RESTRICTED ACCESS
    Lattice instability of the A2BX4-type crystal is studied on the basis of a discrete four sublattice model. The eigenfrequency and the associated eigenvectors of the dynamical matrix at general k values along the a* axis are analytically given. The relation between the wavenumbers at the incommensurate phase transitions, if any, and the interaction coefficients is clarified.
    Download PDF (112K)
  • Ikuyo Shiozaki, Masayoshi Ohashi, Hiroaki Kadowaki
    Article type: General Physics
    Subject area: Mathematical methods in physics.
    2000 Volume 69 Issue 12 Pages 3873-3877
    Published: 2000
    Released on J-STAGE: April 25, 2003
    JOURNAL RESTRICTED ACCESS
    Polycrystal of VOMoO4 has been synthesized by sintering. The electrical resistivity, ρ, was measured with and without magnetic field down to 77 K. The numerical value of ρ is about 5.4 Ω·m at 300 K. The temperature dependent behavior is like as a semiconductor, but the Arhenius plot does not give any constant carriers' excitation energy. Above 100 K ρ behaves as T-n with n of about 5. Magnetic field up to 1 T gives little magnetoresistance and no Hall effect down to 77.2 K. That means the very small mobility of carriers, and suggests the importance of electron-phonon interaction giving the heavy effective mass to carriers. Discussion was made about the relation to the structural instability of crystal, hence, phonon and magnetic instability. Estimation of the electronic state density was tried by molecular orbital calculation with Xα method. It was made sure that only V ions carry the spins. The shape and width of valence band was reasonable compared to measured ones. Energy gap at Fermi level could not be reproduced without electron-phonon interaction term. It was concluded that the current carriers are heavy polarons, whose mobility changes with temperature depending on the change of crystal local symmetry.
    Download PDF (325K)
  • Yoshio Miura, Wilson Agerico Diño, Hideaki Kasai, Ayao Okiji
    Article type: General Physics
    Subject area: Mathematical methods in physics.
    2000 Volume 69 Issue 12 Pages 3878-3884
    Published: 2000
    Released on J-STAGE: April 25, 2003
    JOURNAL RESTRICTED ACCESS
    We perform quantum dynamics calculations that include all six degrees of freedom of a H2 and investigate the effects of the correlation between the molecular diffraction and rotational excitation on the dynamics of H2 scattered from Cu(001). Our calculation results show that when the H2 undergoes diffraction on Cu(001) and assumes helicopter-like rotation, the rotationally inelastic diffraction (RID) probability (with the rotational quantum number j changing from j=0→ 2, and the corresponding azimuthal quantum number mj changing from |mj| = 0→ 2) decreases with increasing incident energies. On the other hand, when the H2 undergoes diffraction on Cu(001) and assumes cartwheel-like rotation, the rotationally inelastic diffraction (RID) (j=0→ 2,mj = 0→ 0) probability increases with increasing incident energies. Upon averaging over all possible orientations (averaging over all possible values of the azimuthal quantum number mj, |mj|=0,1,2), the mj-averaged RID probability shows qualitative features that depend on which type of H2 rotation (helicopter-like or cartwheel-like) dominates at the particular incident energy range considered. Apart from differences due to isotope effects, the qualitative features of the mj-averaged RID probability agree with recent experimental observations for the scattering of D2 on Cu(001).
    Download PDF (325K)
  • Hiroaki Ohtani, Toshio Yamaguchi, Fumiko Yonezawa
    Article type: General Physics
    Subject area: Mathematical methods in physics.
    2000 Volume 69 Issue 12 Pages 3885-3895
    Published: 2000
    Released on J-STAGE: April 25, 2003
    JOURNAL RESTRICTED ACCESS
    The purpose of this paper is to investigate the electronic properties of expanded selenium (Se) near the liquid-vapor critical point by the spin density functional (SDF) method as well as by the density functional (DF) method both with the local density approximation (LDA) and the generalized gradient approximation (GGA). In any case of the four possible sets (DF+LDA, SDF+LDA, DF+GGA and SDF+GGA), our results show that, when some of Se-Se bonds are broken in the process of expanding the system, (1) the bonding levels go upward while the unti-bonding levels go downward for the weakened bonds, and then the energy difference between them is decreased, (2) the energetically smallest states become relatively lowered from the conduction anti-bonding bands, and then the anti-bonding states overlap with the valence lone-pair band, (3) expanded Se finally transforms from a nonmetal to a metal. In this metallic state, the local three-fold structure is formed between the terminal atom of the chain and the neighbor chain. When the system is expanded furthermore, the band width becomes reduced and the spin polarization takes place at the terminal atom of the chain. Further expanded Se transforms to a nonmetal. In the volume region of our interest, the calculated energy levels are the same for any of these four sets. Consequently, the mechanism we have proposed for nonmetal-to-metal transition of expanded Se remains intact even when the calculations are carried out in different methods.
    Download PDF (2110K)
  • Toshifumi Itakura, Yoshikazu Suzumura
    Article type: General Physics
    Subject area: Mathematical methods in physics.
    2000 Volume 69 Issue 12 Pages 3896-3903
    Published: 2000
    Released on J-STAGE: April 25, 2003
    JOURNAL RESTRICTED ACCESS
    Spin density wave (SDW) state at quarter-filling has been examined for two-coupled chains with interchain coupling which is given by a Coulomb repulsion acting on 4kF charge density waves with kF being the Fermi wave number. In terms of the transfer integral method, we study a transverse incommensurability induced by a phase difference δ (a misfit) between two chains. The competition between the intrachain commensurability energy and the interchain interaction, which leads to a crossover from the commensurate state to the incommensurate state, has been demonstrated by evaluating the renormalized interchain phase difference, the probability distribution function of the phase and the correlation of density waves.
    Download PDF (206K)
  • José Sánchez-, Flávio Aristone, Gilmar E. Marques
    Article type: General Physics
    Subject area: Mathematical methods in physics.
    2000 Volume 69 Issue 12 Pages 3904-3911
    Published: 2000
    Released on J-STAGE: April 25, 2003
    JOURNAL RESTRICTED ACCESS
    We introduce an efficient variational method to solve the three-dimensional Schrödinger equation for any arbitrary potential V(x,y,z). The method uses a basis set of localized functions which are build up as a product of three one-dimensional cubic β-splines. We have analysed the accuracy of such a method by studying some exact 3D potentials: the harmonic oscillator, the hydrogen atom and the quantum box. Finally, we have calculated energy levels of GaAs/AlGaAs cubic quantum dots and make a comparison with the ones resulting from two well known simplification schemes based in a decomposition of the full potential problem into three separated one-dimensional problems. We show that the scheme making a sequential decomposition gives eingenvalues in better agreement with exact values here obtained variationally.
    Download PDF (683K)
  • Tetsuro Saso
    Article type: General Physics
    Subject area: Mathematical methods in physics.
    2000 Volume 69 Issue 12 Pages 3912-3916
    Published: 2000
    Released on J-STAGE: April 25, 2003
    JOURNAL RESTRICTED ACCESS
    The two-particle-self-consistent theory is applied to the single-impurity Anderson model. It is found that it cannot reproduce the small energy scale in the strong correlation limit. A modified scheme to overcome this difficulty is proposed by introducing an appropriate vertex correction explicitly. Using the same vertex correction, the self-energy is investigated, and it is found that under certain assumptions it reproduces the result of the modified perturbation theory which interpolates the weak and the strong correlation limits.
    Download PDF (153K)
  • Yasuhiro Saiga, Yoshio Kuramoto
    Article type: General Physics
    Subject area: Mathematical methods in physics.
    2000 Volume 69 Issue 12 Pages 3917-3931
    Published: 2000
    Released on J-STAGE: April 25, 2003
    JOURNAL RESTRICTED ACCESS
    Quasi-particle picture in a magnetic field is pursued for dynamical spin and charge correlation functions of the one-dimensional supersymmetric t-J model with inverse-square interaction. With use of exact diagonalization and the asymptotic Bethe-ansatz equations for finite systems, excitation contents of relevant excited states are identified which are valid in the thermodynamic limit. The excitation contents are composed of spinons, antispinons, holons and antiholons obeying fractional statistics. Both longitudinal and transverse components of the dynamical spin structure factor are independent of the electron density in the region where only quasi-particles with spin degrees of freedom (spinons and antispinons) contribute. The dynamical charge structure factor does not depend on the spin-polarization density in the region where only quasi-particles with charge (holons and antiholons) are excited. These features indicate the strong spin-charge separation in dynamics, reflecting the high symmetry of the model.
    Download PDF (1610K)
  • Vladimir Bubanja
    Article type: General Physics
    Subject area: Mathematical methods in physics.
    2000 Volume 69 Issue 12 Pages 3932-3936
    Published: 2000
    Released on J-STAGE: April 25, 2003
    JOURNAL RESTRICTED ACCESS
    We study the effect of the finite RC line on the electron cotunneling through two serially connected small normal-metal tunnel junctions. We obtain the analytic expressions for the cotunneling current in the cases of small and large line resistance compared to the quantum resistance.
    Download PDF (146K)
  • Katsunori Tagami, Naruo Sasaki, Masaru Tsukada
    Article type: General Physics
    Subject area: Mathematical methods in physics.
    2000 Volume 69 Issue 12 Pages 3937-3942
    Published: 2000
    Released on J-STAGE: April 25, 2003
    JOURNAL RESTRICTED ACCESS
    The features of the chemical interaction between the nanotube tip and the Si(001) surface are investigated based on a self-consistent tight-binding model. When the tip oscillates on top of the up dimer atom, it feels discontinuous changes in the normal force, which are accompanied by drastic transformation of the the dimer structure. These events are explained by switching to the other branches on the potential energy surface. In addition, as long as the tip does not come close to the surface, it is found to become negatively (positively) charged on top of up (down) dimer atom, which is caused by the its interaction to the local density of states of the surface dimer near the fermi level.
    Download PDF (748K)
  • Mitsuaki Takigawa, Masanori Ichioka, Kazushige Machida
    Article type: General Physics
    Subject area: Mathematical methods in physics.
    2000 Volume 69 Issue 12 Pages 3943-3954
    Published: 2000
    Released on J-STAGE: April 25, 2003
    JOURNAL RESTRICTED ACCESS
    On the basis of the microscopic Bogoliubov-de Gennes theory, the dependence of the nuclear spin relaxation time T1 around vortices on the temperature and field is studied comparatively for both s-wave superconductor and d-wave superconductor. Reflecting low energy electronic excitations associated with the vortex core, the dependence of T1 on the site and temperature deviate from those of the zero-field case, and T1 becomes faster with approaching the vortex core. In the core region, T1-1 has a new peak below the superconducting transition temperature Tc. The dependence of the overall T1(T) on the field for s-wave and d-wave superconductors is investigated and analyzed in terms of the local density of states. The NMR study by the dependence of T1 on the resonance field may be a new method to probe the spatial resolved vortex core structure in various conventional and unconventional superconductors.
    Download PDF (1839K)
  • Yoshifumi Onishi, Kazumasa Miyake
    Article type: General Physics
    Subject area: Mathematical methods in physics.
    2000 Volume 69 Issue 12 Pages 3955-3964
    Published: 2000
    Released on J-STAGE: April 25, 2003
    JOURNAL RESTRICTED ACCESS
    Properties of an extended periodic Anderson model with the f-c Coulomb interaction Ufc is studied as a model for CeCu2Ge2 and related compounds which is cosidered to exhibit a sharp valence change under pressure. The problem is treated by extending the slave-boson and large-N expansion method to treat the present system. It is shown that, as the f-level εf is increased relative to the Fermi level, the sharp valence change is caused by the effect of Ufc with moderate strength of the order of the bandwith of conduction electrons. The superconducting transition temperature Tc due to the valence-fluctuation exchange is estimated on the slave-boson fluctuation approximation. In the model with spherical Fermi surface, Tc exhibits sharp peak as a function of εf, simulating the effect of pressure, for the d-wave pairing channel.
    Download PDF (240K)
  • Takahiro Yamamoto, Masanari Asano, Chikara Ishii
    Article type: General Physics
    Subject area: Mathematical methods in physics.
    2000 Volume 69 Issue 12 Pages 3965-3971
    Published: 2000
    Released on J-STAGE: April 25, 2003
    JOURNAL RESTRICTED ACCESS
    The magnetization process of S=1/2 XXZ chain, exposed to a periodic field, have been studied with use of density matrix renormalization group (DMRG) method and Jordan-Wigner fermion mean field approximation. In this study, the DMRG calculation has been performed mainly in case of periodic field with a period four times the lattice spacing. The magnetization curves for various values of Ising anisotropy Δ and amplitude of periodic field λ are obtained, exhibiting a plateau for a suitable set of values of Δ and λ. A phase diagram on the plane of Δ and the uniform field h, or on the plane of Δ and λ, has been constructed to show the condition for the `plateau phase' to appear. These results are well interpreted in terms of the renormalized energy band of JW-fermions, moving in a self-consistent periodic field.
    Download PDF (206K)
  • Taira Kato, Masaru Kato
    Article type: General Physics
    Subject area: Mathematical methods in physics.
    2000 Volume 69 Issue 12 Pages 3972-3979
    Published: 2000
    Released on J-STAGE: April 25, 2003
    JOURNAL RESTRICTED ACCESS
    We study stripe orders of charge and spin density waves in the extended Hubbard model with the nearest-neighbor Coulomb repulsion V within the mean field approximation. We obtain V vs. T (temperature) phase diagram for the on-site Coulomb interaction U/t=8.0 and the filling n=0.8, where t is a nearest-neighbor transfer energy. Our result shows that the diagonal stripe spin density wave state (SDW) is stable for small V, but for large V the most stable state changes to a charge density wave-antiferromagnetic (CDW-AF) state. Especially we find at low temperature and for a certain range of value of V, a vertical stripe CDW-AF state becomes stable.
    Download PDF (2349K)
  • Kazuko Zenmyo, Hidenori Kubo, Hiroyuki Deguchi, Kensuke Konishi, Kazuy ...
    Article type: General Physics
    Subject area: Mathematical methods in physics.
    2000 Volume 69 Issue 12 Pages 3980-3982
    Published: 2000
    Released on J-STAGE: April 25, 2003
    JOURNAL RESTRICTED ACCESS
    In the specific heat measurements of Fe1-xMnxCl2·2H2O with competing exchange interactions and anisotropies, two peaks are observed in Fe-rich region and one sharp peak is observed in Mn-rich region. In the ac susceptibility measurements at a lower temperature than Néel point TN, no anomalies are observed in Fe-rich region and a broad maximum is observed in Mn-rich region. These results imply the existence of “intermediate” phase at the low temperature region.
    Download PDF (168K)
  • Rikio Settai, Kiyohiro Sugiyama, Akinobu Yamaguchi, Shingo Araki, Kous ...
    Article type: General Physics
    Subject area: Mathematical methods in physics.
    2000 Volume 69 Issue 12 Pages 3983-3995
    Published: 2000
    Released on J-STAGE: April 25, 2003
    JOURNAL RESTRICTED ACCESS
    We measured the specific heat, thermal expansion coefficient, magnetization, electrical resistivity, magnetoresistance and de Haas-van Alphen (dHvA) effect in PrSn3. The dense Kondo effect was confirmed from a negative magnetoresistance and the presence of heavy electrons with the cyclotron effective mass of 8–9 m0 for the main Fermi surface. The magnetic phase diagram was also clarified by the high-field magnetization measurement.
    Download PDF (642K)
  • Yutaka Uekusa, Akihide Oguchi
    Article type: General Physics
    Subject area: Mathematical methods in physics.
    2000 Volume 69 Issue 12 Pages 3996-4002
    Published: 2000
    Released on J-STAGE: April 25, 2003
    JOURNAL RESTRICTED ACCESS
    We treat the organic system mMPYNN-BF4 as a network of hexagons. Each hexagon contains six S=1/2 spins coupled alternately with ferro- and antiferromagnetic interactions. The antiferromagnetic coupling between hexagons is treated as a perturbation term. We obtain the ferro- and antiferromagnetic coupling constants in the hexagon and the antiferromagnetic coupling constant between hexagons. The susceptibility calculated by the second-order perturbation method for mMPYNN-BF4 agrees well with the experimental results. The ground state energy is also calculated.
    Download PDF (360K)
  • Kazuo Hida
    Article type: General Physics
    Subject area: Mathematical methods in physics.
    2000 Volume 69 Issue 12 Pages 4003-4007
    Published: 2000
    Released on J-STAGE: April 25, 2003
    JOURNAL RESTRICTED ACCESS
    Low energy spectrum of the S=1 kagomé Heisenberg antiferromagnet (KHAF) is studied by means of exact diagonalization and the cluster expansion. The magnitude of the energy gap of the magnetic excitation is consistent with the recent experimental observation for m-MPYNN·BF4. In contrast to the S=1/2 KHAF, the non-magnetic excitations have finite energy gap comparable to the magnetic excitation. As a physical picture of the ground state, the hexagon singlet solid state is proposed and verified by variational analysis.
    Download PDF (171K)
  • Mohamed Tlemçani, Khadija Benbachir, Salaheddine Sayouri, K. Me ...
    Article type: General Physics
    Subject area: Mathematical methods in physics.
    2000 Volume 69 Issue 12 Pages 4008-4012
    Published: 2000
    Released on J-STAGE: April 25, 2003
    JOURNAL RESTRICTED ACCESS
    We have studied the magnetization of melt spun amorphous Fe100-x-yCrx(PCSi)y alloys with 4 ≤ x ≤ 11 and 19 ≤ y ≤ 22 under magnetic fields up to 18 kOe, and have analyzed the results at 10 K in the framework of the phenomenological model of Chudnovsky and Serota. Behaviour of magnetic moment and exchange and anisotropy constants has been compared to that of the same parameters in amorphous FeNi(BSi), FeNiCr(BSi) and FeV(BSi).
    Download PDF (167K)
  • Kohki Hayashi, Keisuke Tajima, Hidekazu Saito, Kazuaki Fukamichi
    Article type: General Physics
    Subject area: Mathematical methods in physics.
    2000 Volume 69 Issue 12 Pages 4013-4017
    Published: 2000
    Released on J-STAGE: April 25, 2003
    JOURNAL RESTRICTED ACCESS
    The magneto-volume effect in Laves phase compound Lu(Co1-xGax)2 has been studied by an X-ray diffraction technique. The temperature dependence of the volume change for the samples with 0.10 ≤ x ≤ 0.15 has been found to be proportional to the square of magnetization with the same coefficient of the magneto-volume coupling constant. For the sample with x = 0.10, the temperature induced first order transition from the cubic to the tetragonal structure has been observed. Above the Curie temperature, a discontinuous change of the lattice parameter is also observed by applying magnetic field. The results can be described by a spin fluctuation theory for itinerant electron metamagnets. The temperature and magnetic field induced first order phase transitions observed in the sample with x = 0.10 are characterized by the coexistence of two phases in a wide temperature or magnetic field range without an appreciable hysteresis.
    Download PDF (185K)
  • Yoshinori Takahashi, Takeshi Kanomata, Ryunosuke Note, Tomohiro Nakaga ...
    Article type: General Physics
    Subject area: Mathematical methods in physics.
    2000 Volume 69 Issue 12 Pages 4018-4025
    Published: 2000
    Released on J-STAGE: April 25, 2003
    JOURNAL RESTRICTED ACCESS
    The precise measurements of the specific heat have been done on high-quality samples of FeSi and CoSi with the B20 crystal structure. The magnetic and electronic contributions are extracted by explicitly subtracting phonon contributions. The results are discussed based on the spin fluctuation theory for itinerant electron magnets.
    Download PDF (170K)
  • Toshikazu Nakamura
    Article type: General Physics
    Subject area: Mathematical methods in physics.
    2000 Volume 69 Issue 12 Pages 4026-4033
    Published: 2000
    Released on J-STAGE: April 25, 2003
    JOURNAL RESTRICTED ACCESS
    The low temperature magnetic properties in the quasi-one-dimensional system, (EDT-TTF)2AuBr2, were investigated by using 1H-NMR and ESR techniques. (EDT-TTF)2AuBr2 undergoes an SDW transition at 16 K. At 6 K, an anomalous second-peak of 1H-NMR spin-lattice relaxation rate, 1H-T1-1, in the SDW phase has been observed. An additional increase of 1H-NMR absorption line and gradual decrease of spin-spin relaxation rate, 1H-T2-1, were observed below 6 K. The magnetic properties of the SDW phase observed in the present salt are discussed from microscopic points of view.
    Download PDF (224K)
  • Yoshihiro Koike, Naoto Metoki, Yukio Morii, Tatsuo Kobayashi, Tomohiko ...
    Article type: General Physics
    Subject area: Mathematical methods in physics.
    2000 Volume 69 Issue 12 Pages 4034-4042
    Published: 2000
    Released on J-STAGE: April 25, 2003
    JOURNAL RESTRICTED ACCESS
    Neutron scattering experiments were carried out in order to investigate the field-induced antiferromagnetic long-range order and spin dynamics for the new Haldane compounds Ni(C5H14N2)2N3(ClO4) (NDMAZ) and Ni(C5H14N2)2N3(PF6) (NDMAP). We observed the energy gaps corresponding to the excited triplet, Δ x = 1.61 meV, Δ y = 1.76 meV, Δ z = 3.2 meV for NDMAZ and Δ x = 0.48 meV, Δ y = 0.64 meV for NDMAP. The dispersion in NDMAZ was well explained by the theoretical curve with the intra-chain interaction J = 50 K. The field dependence of the gap energy below critical field (Hc), was observed for NDMAZ and NDMAP as applying the field perpendicular to the chain direction. The field dependence of the excitation levels in NDMAZ was well explained by the fermionic field-theory treatment of the one-dimensional Heisenberg antiferromagnetic Hamiltonian with these gap energies and g-value, 2.3. In NDMAP, we found that the excitation peaks at Q = (0 0 0.5) became unobservably weak above Hc. This result would indicate a level crossing between the ground and the excited level at Hc and the change of the ground state above Hc. No trace of the magnetic Bragg peak due to the field induced ordering could be observed in the present study with our non-deuterated single crystal sample.
    Download PDF (332K)
  • Akira Ogasahara, Seiji Miyashita
    Article type: General Physics
    Subject area: Mathematical methods in physics.
    2000 Volume 69 Issue 12 Pages 4043-4048
    Published: 2000
    Released on J-STAGE: April 25, 2003
    JOURNAL RESTRICTED ACCESS
    Electron spin resonance in an antiferromagnetic cluster is studied by a direct numerical method to obtain the dynamical susceptibility χ”(ω) expressed by the Kubo formula. Temperature dependence of the dipolar broadening is investigated in the isotropic Heisenberg model. The width decreases monotonically as the temperature decreases in the case of high frequency. In the case of low frequency, however it is found to show non-monotonic dependence. The frequency- and temperature-dependence of the resonant field of Ising-like Heisenberg model is studied, and it is compared with the conventional antiferromagnetic resonance (AFMR). It is found that the paramagnetic resonance (PMR) coexists with the antiferromagnetic resonance in the wide range of the temperature when the field is applied parallel to the easy axis. A branch of the conventional AFMR is found to split into double peaks. In the case of the field perpendicular to the easy axis, PMR is very broad and disappears at low temperature.
    Download PDF (237K)
  • Rie Haruki, Makoto Seto, Shinji Kitao, Yoshitaka Yoda, Yutaka Maeda
    Article type: General Physics
    Subject area: Mathematical methods in physics.
    2000 Volume 69 Issue 12 Pages 4049-4054
    Published: 2000
    Released on J-STAGE: April 25, 2003
    JOURNAL RESTRICTED ACCESS
    Nuclear resonant quasielastic scattering from ferrous cations in ion-exchange Nafion membranes was measured at room temperature, and the intrinsic dynamics of the cations inside the spherical regions surrounded by the sulfonic groups of Nafion was studied. For the analysis, the formula of nuclear resonant absorption for a particle diffusing in a sphere with an impermeable surface was derived. The formula indicates that the effect of the surface upon the diffusive motion is small if the radius of the sphere is larger than a critical value; in the case of 57Fe ions, the value is about 2 Å. As the radius of the spherical regions in our Nafion samples is estimated to be about 5 Å, the existence of the surface can be ignored and the intrinsic dynamics of Fe cations can be extracted. The diffusion coefficient estimated from the least squares fit was (1.12±0.13)×10-5 cm2/s for 15 wt% water content. This value is in good agreement with that of Fe cations in an HCl solution. As a result, Fe cations in Nafion diffuse as freely as those in solutions.
    Download PDF (166K)
  • Fuminao Shimizu, Toshihisa Yamaguchi, Masaaki Takashige
    Article type: General Physics
    Subject area: Mathematical methods in physics.
    2000 Volume 69 Issue 12 Pages 4055-4059
    Published: 2000
    Released on J-STAGE: April 25, 2003
    JOURNAL RESTRICTED ACCESS
    Dielectric properties of ferroelectric Rb2CdI4 were investigated. Since it is well known that the crystal surface reacts chemically with silver paste electrode and it makes dielectric quantities unstable, we reexamined dielectric properties using the sample with evaporated gold electrode. As the result, we obtained the stable results of the temperature dependence of the dielectric constant and pyroelectric charge. The experimental data established that ferroelectric Curie point of Rb2CdI4 is 211 K and the spontaneous polarization Ps is about 0.4 μC/cm2 around 4 K. The frequency dispersion of the dielectric constant was also observed below the Curie point but its origin is still open.
    Download PDF (211K)
  • Young-Tak Chough, Hyunchul Nha, Kyungwon An
    Article type: General Physics
    Subject area: Mathematical methods in physics.
    2000 Volume 69 Issue 12 Pages 4060-4065
    Published: 2000
    Released on J-STAGE: April 25, 2003
    JOURNAL RESTRICTED ACCESS
    We review a non-resonant Jaynes-Cummings system where the two-state atom is driven by an external field of arbitrary frequency. We identify the multiphoton resonances in the Jaynes-Cummings Ladder (JCL) system, and thereby explain all the “resonance” peaks at far-off resonant frequencies.
    Download PDF (215K)
  • Tadashi Kawamoto, Takehiko Mori, Takashi Yamamoto, Hiroyuki Tajima, Yo ...
    Article type: General Physics
    Subject area: Mathematical methods in physics.
    2000 Volume 69 Issue 12 Pages 4066-4070
    Published: 2000
    Released on J-STAGE: April 25, 2003
    JOURNAL RESTRICTED ACCESS
    (TTM-TTP)AuI2 (TTM-TTP: 2,5-bis[4,5-bis(methylthio)-1,3-dithiol-2-ylidene]-1,3,4,6-tetra-thiapentalene) has a dimerized structure along the donor stacking direction, and shows semiconducting behavior below room temperature. ESR, static magnetic susceptibility, and optical reflectance of this salt have been measured to investigate the spin state and the electronic correlation. The ESR signal has been observed from room temperature to 3 K, and the spin susceptibility shows paramagnetic behavior with a rapid decrease below 10 K. The static magnetic susceptibility is paramagnetic and has an anomaly around 10 K in agreement with the ESR result. The chain axis optical reflectance spectra show clear optical gap in the mid-infrared region. An attempt is undertaken to analyze the optical spectrum by means of the one-dimensional dimerized Hubbard model, which suggests that the on-site Coulomb repulsion, U, is small and the spin polarization is located at the marginal paramagnetic boundary. These results indicate that this compound is not a band-insulator but the Mott insulator with a small spin gap.
    Download PDF (172K)
  • Makoto Nakazawa, Haruhiko Ogasawara, Akio Kotani
    Article type: General Physics
    Subject area: Mathematical methods in physics.
    2000 Volume 69 Issue 12 Pages 4071-4077
    Published: 2000
    Released on J-STAGE: April 25, 2003
    JOURNAL RESTRICTED ACCESS
    We calculate the Ce 4ƒ → 3d resonant X-ray emission spectroscopy (4ƒ → 3d RXES) of Ce compounds, CeF3 and CeO2, by means of ionic and impurity Anderson model with full multiplet effects, respectively. The calculation is based on the second-order optical formula, and the effect of the X-ray polarization is taken into account. The calculated results of 4ƒ → 3d RXES show the strong dependence on the X-ray polarization, as well as on the scattering angle. Using the selection rule of the dipole transition with polarized X-rays, the calculated spectral features are explained.
    Download PDF (300K)
  • Aleksandra B. Djurišic, E. Herbert Li
    Article type: General Physics
    Subject area: Mathematical methods in physics.
    2000 Volume 69 Issue 12 Pages 4078-4086
    Published: 2000
    Released on J-STAGE: April 25, 2003
    JOURNAL RESTRICTED ACCESS
    We have modeled the dielectric function of wurtzite AlxGa1-xN alloys for normal polarization in the energy range up to 10 eV and for all compositions 0 ≤ x ≤ 1. The employed model takes into account one-electron contributions to the dielectric function at E0, E1A, E1B, and E1C critical points, as well as excitonic contributions at those critical points. The model is very flexible, due to the use of adjustable broadening function instead of the conventional Lorentzian one. Model parameters are determined by acceptance-probability-controlled simulated annealing. We obtain excellent agreement with the experimental data for all available compositions.
    Download PDF (339K)
  • Jun-ichi Igarashi, Manabu Takahashi
    Article type: General Physics
    Subject area: Mathematical methods in physics.
    2000 Volume 69 Issue 12 Pages 4087-4094
    Published: 2000
    Released on J-STAGE: April 25, 2003
    JOURNAL RESTRICTED ACCESS
    We analyze the recent experiment [W. Neubeck et al.: Phys. Rev. B 60 (1999) R9912] for the resonant x-ray magnetic scattering (RXMS) around the K edge of Co in the antiferromagnet CoO. We propose a mechanism of the RXMS that makes the 4p states couple to the magnetic order: the intraatomic exchange interaction between the 4p and the 3d states and the p-d mixing to the 3d states of neighboring Co atoms. These couplings induce the orbital moment in the 4p states and make the scattering tensor antisymmetric. Using a cluster model, we demonstrate that this modification gives rise to a large RXMS intensity in the dipole process, in good agreement with the experiment. We also find that the pre-edge peak is generated by the transition to the 3d states in the quadrupole process, with negligible contribution of the dipole process. We also discuss the azimuthal angle dependence of the intensity.
    Download PDF (290K)
  • Yoshitaka Tanimura, Thomas Steffen
    Article type: General Physics
    Subject area: Mathematical methods in physics.
    2000 Volume 69 Issue 12 Pages 4095-4106
    Published: 2000
    Released on J-STAGE: April 25, 2003
    JOURNAL RESTRICTED ACCESS
    The relaxation processes in a quantum system nonlinearly coupled to a harmonic Gaussian-Markovian heat bath are investigated by the quantum Fokker-Planck equation in the hierarchy form. This model describes frequency fluctuations in the quantum system with an arbitrary correlation time and thus bridges the gap between the Brownian oscillator model and the stochastic model by Anderson and Kubo. The effects of the finite correlation time and the system-bath coupling strength are studied for a harmonic model system by numerically integrating the equation of motion. The one-time correlation function of the system coordinate, which is measured in conventional Raman and infrared absorption experiments, already reflects the inhomogeneous character of the relaxation process. The finite correlation time of the frequency fluctuations, however, is directly evident only in the two- and three-time correlation function as probed by multidimensional spectroscopic techniques such as the Raman echo and the fifth-order 2D Raman experiment.
    Download PDF (365K)
  • Feng Liu, YuGuo Yu, Wei Wang
    Article type: General Physics
    Subject area: Mathematical methods in physics.
    2000 Volume 69 Issue 12 Pages 4107-4111
    Published: 2000
    Released on J-STAGE: April 25, 2003
    JOURNAL RESTRICTED ACCESS
    Many studies have recently focused on the temporal encoding scheme, wherein information about a stimulus is carried in temporal firing patterns of neurons. We first show how to quantify the information conveyed in the spike train of an individual neuron and that in the temporal firing patterns of an ensemble of neurons, respectively, in terms of the entropy. We further apply both the information representations to the context of stochastic resonance. It is demonstrated that the neurons can transmit more information about the signals with frequencies within the range of 22–70 Hz. These enable us to well interpret the experimental observations.
    Download PDF (230K)
  • Masami Kanazawa, Nobuo Tsuda
    Article type: General Physics
    Subject area: Mathematical methods in physics.
    2000 Volume 69 Issue 12 Pages 4112-4113
    Published: 2000
    Released on J-STAGE: April 25, 2003
    JOURNAL RESTRICTED ACCESS
    Download PDF (93K)
  • Yosuke Higuchi, Hitoshi Sugawara, Yuji Aoki, Hideyuki Sato
    Article type: General Physics
    Subject area: Mathematical methods in physics.
    2000 Volume 69 Issue 12 Pages 4114-4115
    Published: 2000
    Released on J-STAGE: April 25, 2003
    JOURNAL RESTRICTED ACCESS
    Download PDF (93K)
feedback
Top