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Ruihong Yue, Ryu Sasaki
Subject area: Mathematical methods in physics.
1998 Volume 67 Issue 9 Pages
2967-2969
Published: September 01, 1998
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For a one-dimensional SU(n) Hubbard model, a pair of Lax operators arederived, which give a set of fundamental equations for the quantum inversescattering method under both periodic and open boundary conditions. Thisprovides another proof of the integrability of the model under theperiodic boundary condition.
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Yoshihiro Yamazaki
Subject area: Statistical physics and thermodynamics.
1998 Volume 67 Issue 9 Pages
2970-2973
Published: September 01, 1998
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We performed numerical simulationsfor pattern formations in cubic-tetragonal structural transitions.Our model can reproduce a series of patterns which are quite similar to morphologies observed in experiments.And the evolution of patterns is consistentwith the results of the interface dynamics.The mechanism of pattern formations is discussedfrom an elastic point of view.
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Tsuyoshi Hondou, Fumiko Takagi
Subject area: Statistical physics and thermodynamics.
1998 Volume 67 Issue 9 Pages
2974-2976
Published: September 01, 1998
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We consider the Langevin dynamics which describes the transducerof thermal fluctuation into mechanical work.In the frame of Feynman's ratchet, we prove that irreversiblityis unavoidable in operating the transducer if the system is described by the conventional Langevin equation with two degrees of freedom, where the degrees correspond to two heat baths of different temperatures.
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Sadao Masamune, Motomi Iida, Katsumi Ohta, Hiroshi Oshiyama
Subject area: The physics of plasmas and electric discharges.
1998 Volume 67 Issue 9 Pages
2977-2980
Published: September 01, 1998
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An analytical formula has been derived for the magnetic island width in a helically perturbed force-free equilibrium with uniform force-free parameters.In this calculation, the effect of the nonlinear plasma response to the resultant field configuration has been self-consistentlytaken into account up to the first order. The radial magnetic field at the resonant surface is amplifiedas a result of the nonlinear plasma response, or, themagnetohydrodynamic (MHD) relaxation.Typical width of the core island is 10% of the plasma radius for the perturbation level of 1% at the edge, and the inner island is larger than the outer one when compared at the sameperturbation level at the edge.Usefulness of the formula is demonstrated by comparing theexperimental results with the theoretical calculation.
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Jun–ichiro Suda, Tomoo Nakayama, Mitsugu Matsushita
Subject area: Structure of liquids and solids; crystallography.
1998 Volume 67 Issue 9 Pages
2981-2983
Published: September 01, 1998
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We have studied the effect of salts, adenosine triphosphate (ATP) and glycoprotein on the growth of huge right-handed spiral crystals of potassium dichromate (K
2Cr
2O
7) in gelatin gel. These materials are known to induce, respectively, amorphous, short-range and long-range arrangements of collagen macromolecules that constitute the gelatin-gel network. It was revealed that both salts and ATP have a clear tendency to reduce the spiral growth of K
2Cr
2O
7, while glycoprotein strongly enhances it. These results suggest that not only the existence of collagen macromolecules with right-handed triple helix structure but also their long-range arrangement is essential for the spiral growth of K
2Cr
2O
7.
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Takashi Onozuka, Komajiro Niizeki
Subject area: Structure of liquids and solids; crystallography.
1998 Volume 67 Issue 9 Pages
2984-2987
Published: September 01, 1998
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Variation of the lattice-modulation period p
a of the “incommensurate” phase Bi
2Br
2(Ca
1-xPr
x)Cu
2O
8+δ (0≤ x≤ 0.72) with Pr-concentration x was examined by electron diffraction. The plot of p
a versus x exhibits roughly a linear decrease but it has a staircase structure. The period of each stair, p
a, agrees with a value expected for a commensurate structure. We observed nine stairs which are symmetrically arranged; the central stair corresponds to the primary structure with a simple modulation, and a stair on the left (or right) corresponds to a structure which is derived from the primary structure by introducing an advanced (or delayed) discommensuration. The observed structures cover a full range of commensurate structures predicted theoretically.
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Akira Shimizu, Jun–ichi Inoue
Subject area: Quantum fuids and solids: liquid and solid helium.
1998 Volume 67 Issue 9 Pages
2988-2991
Published: September 01, 1998
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We analyze the condensation of interacting bosonsconfined in a finite volume V, by evaluating the time evolution of the density operator \hat{ρ}(t) in the case where the number of bosons is exactly fixed for t < 0and a small leakage occurs for t ≥q 0.We identify a “natural coordinate” \hat{b}
0 of interacting bosons, using which many physical properties can be simply described.In particular, the time evolution of \hat{ρ}(t) can be simply described as the evolution from the number state, to a phase-randomized mixture (PRM) of “number-phase squeezed states”, and finally to the PRM of coherent states, of \hat{b}
0.The order parameter, defined as the expectation value of the boson field, of each element of the PRM grows rapidly from zero to the full value.
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Shunji Sugai, Nobumasa Kitamori, Syoichi Hosoya, Kazuyoshi Yamada
Subject area: Electron states in condensed matter.
1998 Volume 67 Issue 9 Pages
2992-2995
Published: September 01, 1998
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Separation of spin and charge densities in La
2NiO
4+δ was investigated using Raman scattering. Magnetic and electronic Raman scattering in La
2NiO
4+δ with δ=0.02 and δ=0.15 has a large continuum below 1500 cm
-1. As temperature decreases to below 250 K at δ=0.15, the scattering intensity below 650 cm
-1 moves into the high-energy range and simultaneously the intensity at the energy of the undoped two-magnon peak increases, as expected from the separation of spin and charge densities. Similar effects are also observed even at the low carrier concentration of δ=0.02 below 150 K. This indicates that the spin and charge densities separate even at the low carrier concentration of δ=0.02.
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Satoshi Nishimoto, Yukinori Ohta
Subject area: Electron states in condensed matter.
1998 Volume 67 Issue 9 Pages
2996-2999
Published: September 01, 1998
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Based on recent experimental evidences that the electronic charge degrees of freedom play an essential role in the spin-Peierls--like phase transition of NaV
2O
5, we first make the mapping of low-energy electronic states of the d-p model for NaV
2O
5 to the quarter-filled t-J ladder with anisotropic parameter values between legs and rungs, and then show that this anisotropic t-J ladder is in the Mott insulating state, the lowest-energy states of which can be modeled by the antiferromagnetic Heisenberg chain with the effective exchange interaction J
eff whose value is consistent with experimental estimates. We furthermore examine the coupling between the ladders as the trellis lattice model and show that the nearest-neighbor Coulomb repulsion on the zigzag-chain bonds can lead to the instability in the charge degrees of freedom of the ladders.
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Fangzhun Guo, Keizo Murata, Harukazu Yoshino, Suguru Maki, Satoru Tana ...
Subject area: Electronic transport in condensed matter.
1998 Volume 67 Issue 9 Pages
3000-3002
Published: September 01, 1998
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The anion ordering in (TMTSF)
2ClO
4 as a function of pressure was examined up to 1.1 GPa by detecting the anomaly in the temperature dependence of resistance under pressure. It turned out that the anion ordering transition was observed up to at least 1.1 GPa by means of an extremely careful control of the rate of slow cooling (< 5 K/h). It is remarkable that the temperature of anion ordering was found to increase up to 41 K, while the strength of the transition determined by the magnitude of resistivity anomaly was reduced.
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Yositake Takane
Subject area: Electronic transport in condensed matter.
1998 Volume 67 Issue 9 Pages
3003-3005
Published: September 01, 1998
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Phase relaxation time τ
φ due to Coulomb interactions is studied semiclassically for electrons in open chaotic billiards with two leads of width W. When W is much larger than the Fermi wavelength λ
F, the phase relaxation time at temperature T is shown to be τ
φ-1=c(λ
F/W)T, where c is a numerical constant of the order of unity. The behavior τ
φ∝ T
-1, similar to that in two-dimensional diffusive systems, is in agreement with the experimental results.
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Jun Goryo, Kenzo Ishikawa
Subject area: Superconductivity.
1998 Volume 67 Issue 9 Pages
3006-3009
Published: September 01, 1998
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We analyze time-reversal-violating processes of the p-wavesuperconductor.The Landau-Ginzburg effective action has an induced T-violating term of electromagnetic potentials which resembles the Chern-Simons term and causes mixing between the electric and magnetic fields. Several T-violating electromagnetic phenomena caused by this term, such as an unusualMeissner effect, the Hall effect without a magnetic field, and Faraday rotation without a magnetic field are investigated.
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Aya Tobo, Atsuko Ito
Subject area: Magnetic properties and materials.
1998 Volume 67 Issue 9 Pages
3010-3013
Published: September 01, 1998
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The field-cooled magnetization M
FC of the cluster-glassFe
0.25Mg
0.75TiO
3 clearly changes with time below the peaktemperature of the zero-field-cooled magnetization M
ZFC, althoughM
FC of most spin-glass systems is almost time-independent andreversible with regard to temperature change across the freezingtemperature. We have examined the aging phenomena of M
FC ofFe
0.25Mg
0.75TiO
3 by investigating the effect of thetemperature cycle on the relaxation of M
FC. After the negativetemperature cycle, the spin system is restored to the configuration beforethe temperature cycle. On the other hand, the spin configuration after thepositive temperature cycle is completely different from that before thetemperature cycle. These results are explained by the hierarchicalorganization in phase space.
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Yoshitaka Murata, Keiji Takeda, Taketoshi Sekine, Masao Ogata, Kunio A ...
Subject area: Magnetic properties and materials.
1998 Volume 67 Issue 9 Pages
3014-3017
Published: September 01, 1998
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The effect of high pressure on the quantum tunneling of magnetization (QTM) in the single-molecule magnet, Mn
12 acetate (Mn
12O
12(O
2CCH
3)
16(H
2O)
4), was studied at 2.4K. As the pressure is increased, the QTM is suppressed significantly with a slight high-field shift of the resonance field that indicates an increase in the height of the potential barrier between the up- and down-spin states. At a maximum pressure of 1.0, GPa, the QTM rate decreases by 50%, while the resonance field increases by 3.5%. The observed pressure dependence can be quantitatively interpreted in terms of the thermally-activated QTM mechanism.
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Yutaka Itoh, Masahiro Matsumura, Hideki Yamagata
Subject area: Magnetics resonances and relaxations in condensed matter; MÖssbauer effect.
1998 Volume 67 Issue 9 Pages
3018-3020
Published: September 01, 1998
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We found a nearly √ {T} dependence of the planar
63Cu nuclear spin-lattice relaxation rate 1/T
1 for the
63Cu-enriched overdoped La
2-xSr
xCuO
4 (x=0.23; T
c-- 20, K), using the
63Cu NMR spin-echo technique. Considering both the transport and the magnetic properties, we conclude that the overdoped compound with x=0.23 is a three-dimensional nearly antiferromagnetic metal. The results indicate that a crossover in the antiferromagnetic spin fluctuation spectrum from two to three dimensions occurs as the Sr content increases beyond x-- 0.20. This is consistent with the dimensional crossover in conduction suggested from the results of electrical resistivity measurements.
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Toshihiko Ono
Subject area: Mathematical methods in physics.
1998 Volume 67 Issue 9 Pages
3021-3025
Published: September 01, 1998
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This paper presents a generalizedRiemannian-geometric method that describes the Lie-Poissonequations of motion for several Hamiltonian systems as the geodesic equations on corresponding Lie groups endowed with theinduced Riemannian structures to investigate instability andto predict some global properties of these systems.
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Kiyoshi Sogo, Shigeki Ichimura
Subject area: Mathematical methods in physics.
1998 Volume 67 Issue 9 Pages
3026-3030
Published: September 01, 1998
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Metastable state is found in nematic liquid crystals under magnetic field. The solution is expressed exactly by Jacobi's elliptic functions. Methods to realize such state experimentally are proposed.
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Kazuaki Nakayama
Subject area: Mathematical methods in physics.
1998 Volume 67 Issue 9 Pages
3031-3037
Published: September 01, 1998
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A formulation on the motion of curves in hyperboloids in the 4-dimensional Minkowski space is presented. It includes many equations integrable by means of the (1+1)-dimensional AKNS inverse scattering scheme. Examples are: the Nonlinear Schrödinger equation of defocusing type, the KdV equation, the Regge-Lund equation and its hyperbolic type.
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Masato Hisakado
Subject area: Mathematical methods in physics.
1998 Volume 67 Issue 9 Pages
3038-3043
Published: September 01, 1998
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We consider (coupled) Davey-Stewartson (DS) system and its Bäcklund transformations (BT). Relations among the DS system, the double Kadomtsev-Petviashvili (KP) system and the Ablowitz-Ladik hierarchy (ALH) are established. The DS system and the double KP system are equivalent. The ALH is the BT of the DS system in a certain reduction. {From} the BT of coupled DS system we can obtain new coupled derivative nonlinear Schrödinger equations.
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Biswanath Rath
Subject area: Mathematical methods in physics.
1998 Volume 67 Issue 9 Pages
3044-3049
Published: September 01, 1998
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A new approach to non-relativistic large order perturbation theory for constructing energy and wave function correction up to Kth order has been developed. Convergent argument of this series has been demonstrated for the ground state of second order and fourth order Schroedinger equation. Further a comparison with the Bender and Wu computational work reflects that the present series is not the same as Rayleigh-Schroedinger perturbation series.
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Yasushi Ishii
Subject area: Statistical physics and thermodynamics.
1998 Volume 67 Issue 9 Pages
3050-3054
Published: September 01, 1998
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A system of spherical particleswith dipoles moving in a plane is studied by Monte-Carlo simulation. The particles interact with each other through the long-range dipole interaction and an appropriate core repulsive potential.The anisotropy in the dipole interaction favors a chain-likestructure of particles with the dipoles oriented along the chain.Growth of chain-like aggregates and the uniaxial (nematic) ordering of the system as well as the ordering of dipolesare investigated as functions of temperature.It is concluded that neither the dipolar ordering nor the uniaxial bond-orientational one can be long-ranged in a thermodynamical system.
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Daisuke Katsuragi
Subject area: Statistical physics and thermodynamics.
1998 Volume 67 Issue 9 Pages
3055-3060
Published: September 01, 1998
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We study the onset of a coherent state in coupled map lattices with global couplings among the mixture of two kinds of oscillators; the logistic oscillator g(x) = rx(1-x) and the tent oscillator g(x) = \frac{r}{4} - \frac{r}{2} | x-½ |. The number of logistic oscillators is kept fixed, and that of tent oscillators is varied by changing the total number of oscillators. It is shown that for certain values of r investigated, the onset of a coherent state among the logistic oscillators in the heterogeneous systems occurs with a smaller coupling strength than that in the homogeneous system.
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Hiroyasu Toyoki
Subject area: Statistical physics and thermodynamics.
1998 Volume 67 Issue 9 Pages
3061-3065
Published: September 01, 1998
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Macroscopic director patterns in the phase ordering process andequilibrium state of nematic liquid crystals under a hybrid boundaryconditions are numerically studied. A new cell-dynamics model fornematic liquid crystals including anisotropic elastic constants is used. Competition between bulk and surface elastic energies yields periodicmodulated equilibrium structures. String-like deformation betweenboojums is found when uniaxial anisotropy is present on a boundary.
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Tomotoshi Nishino, Kouichi Okunishi
Subject area: Statistical physics and thermodynamics.
1998 Volume 67 Issue 9 Pages
3066-3072
Published: September 01, 1998
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We generalize the corner transfer matrix renormalization group, whichconsists of White's density matrix algorithm and Baxter'smethod of the corner transfer matrix, to three dimensional (3D) classicalmodels. The renormalization group transformation is obtained through the diagonalization of density matrices for a cubic cluster.A trial application to 3D Ising model with m = 2 is shown as thesimplest case.
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Kunihiro Okada, Michiharu Wada, Takashi Nakamura, Ryoichi Iida, Shunsu ...
Subject area: Experimentally derived information on atoms and molecules: instrumentation and techniques.
1998 Volume 67 Issue 9 Pages
3073-3081
Published: September 01, 1998
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Laser-microwave double-resonance spectroscopy of laser-cooled
9Be
+ ions in a linear Paul trap has been performed aiming at the development of both highly sensitive and precise methods to be applied to the unstable isotopes.By the alternative irradiation of laser and microwave radiation (pulsed-wavemethod), high accuracy of 4× 10
-7 was obtained in the measurement of the ground-statemagnetic-dipole hyperfine constant (A) of
9Be
+ ionin a weak magnetic field. By the continuous-wave method, high sensitive detection of the microwave resonance was demonstrated. These methods can becomplementarily applied to the measurements of unknown hyperfine constants of the unstable isotopes for studying the hyperfine anomaly.
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Takasi Endo, Eitaro Morimoto, Yutaka Hirayoshi, Kouichi Toyoshima
Subject area: Optics.
1998 Volume 67 Issue 9 Pages
3082-3085
Published: September 01, 1998
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Two LEDs (light emitting diodes) were drived by a constant-current source.Photocurrents from the two LEDs were measured and found to be anticorrelated owing to the shot-noise suppression due to the high impedance of the source.The correlations of the photocurrents are explained by a simple equivalent circuit.
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Behzad Haghighi, Ali Maghari, Mohsen Najafi
Subject area: Kinetic and transport theory of fluids; physical properties of gases.
1998 Volume 67 Issue 9 Pages
3086-3089
Published: September 01, 1998
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An inversion procedure has been used to obtain, from the extended law of corresponding states, the intermolecular potential energy functions for SF
6-Ar, SF
6-Kr and SF
6-Xe over a range of reduced temperature extending from 1 to 100. These directly determined potentials are in good agreement with HFD-type potentials proposed by Taylor et al.
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Masayasu Sato, Nobuaki Isei, Shinichi Ishida, Akihiko Isayama
Subject area: The physics of plasmas and electric discharges.
1998 Volume 67 Issue 9 Pages
3090-3099
Published: September 01, 1998
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The importance of the relativistic frequency down-shift and the optical thickness is pointed out in the determination of the electron temperature profile from electron cyclotron emission (ECE) measurement in the medium electron temperature region. These effects cause a pseudo radial displacement (Δr) of the obtained electron temperature profile. The pseudo displacement depends on only three parameters (the electron temperature, T
e, the optical depth, τ, and the major radius, R). In order to correct the radial position in any tokamak, a scaling law of the displacement is derived as Δr (m)=0.0009 R (m) T
e (keV) (1+40/(5τ )). This scaling law is applicable to the plasma with τ >5 where the error is less than 0.5% of the major radius.
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Tetsuyuki Kubota, Sanae–I. Itoh, Masatoshi Yagi, Kimitaka Itoh
Subject area: The physics of plasmas and electric discharges.
1998 Volume 67 Issue 9 Pages
3100-3106
Published: September 01, 1998
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Dynamics of collapse in a giant ELM (Edge Localized Mode) is presented. A model of transport bifurcation between the H-mode and the magnetic braiding mode (M-mode) is applied to the simulational study of edge plasma dynamics. The bifurcation contains the hysteresis characteristics. The pressure profile development, the propagation of the bifurcation (transition) fronts and the resultant bursting fluxes are obtained. The appearance of a pivot point in the pressure profile, an avalanche followed to the transition front propagation, and the structure of the burst are shown.
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Seishu Lee, Harukazu Iguchi, Akihide Fujisawa, Thomas P. Crowley, Yasu ...
Subject area: The physics of plasmas and electric discharges.
1998 Volume 67 Issue 9 Pages
3107-3113
Published: September 01, 1998
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A heavy ion beam probe (HIBP) is a unique diagnostic instrument which can measure local plasma potential and its fluctuations. However, in the presence of MHD activities, acceleration or deceleration of both primary and secondary beams are caused by the fluctuating vector potential ∂ A/∂ t along the beam trajectories (path integral effect). Such effect possibly induces a contamination to space potential measurement. We have evaluated those effects during a bursting MHD instability in the Compact Helical System (CHS), which is considered to be an m/n=2/1 interchange instability. In this procedure, the vector potential profile is estimated both theoretically and experimentally. Contribution from path effect is found to be less than several percent to the measured space potential fluctuation. Then space potential fluctuation is found to be localized around q=2 magnetic surface, which is consistent with a model for the interchange mode.
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Jun Kokubun, Tugumi Nagano, Masaru Kuribayashi, Kohtaro Ishida
Subject area: Structure of liquids and solids; crystallography.
1998 Volume 67 Issue 9 Pages
3114-3118
Published: September 01, 1998
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The “forbidden reflection” intensity excited due to the ATS (anisotropy of tensor of susceptibility) in a FeS
2 (pyrite) crystal was measured for X-ray energy near the Fe, K-absorption edge from 15, eV below the edge to 65, eV above the edge. In the region above the edge, the ATS intensities for (001), (003) and (011) reflections showed essentially the same energy dependence, two sharp peaks and one broad peak. But below the edge, the energy spectra of the ATS intensity depend on the reflection plane. The azimuthal angle dependence of the intensity cannot be explained by the calculation based on only the dipole transition. Therefore, the scattering is affected by quadrupole transition.
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Masaaki Isobe, Eiji Takayama–Muromachi
Subject area: Structure of liquids and solids; crystallography.
1998 Volume 67 Issue 9 Pages
3119-3124
Published: September 01, 1998
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In order to find the most stable distribution of hole carriers, the bond-valence-sum (BVS) and the electrostatic energy for a composite crystal Ca
13.6Sr
0.4Cu
24+yO
41+z (y=-0.017 and z=-0.035) were calculated using modulated structure data at ambient pressure and room temperature. The BVS calculation suggests that at least four holes per molecule stay in the 1-D chain. The lowest Madelung energy was given from a hole distribution in which all of the self doped holes occupy the sites in the 1-D chain. However, transfer of one hole to the ladder per molecule costs only about 0.7, eV/mol. Considering experimental uncertainties in the structural parameters or contribution of other terms such as kinetic energy to the total energy, it is implied that a small number of holes can be transferred into the ladder. In the 1-D chain, the hole tend to be localized in every other copper site or its adjacent oxygen sites by the structural modulation reflecting the Coulomb interaction between them.
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Susumu Isida, Masaru Suzuki, Sakae Todo, Nobuo Mori, Kiiti Siratori
Subject area: Mechanical and acoustical properties of condesed matter.
1998 Volume 67 Issue 9 Pages
3125-3129
Published: September 01, 1998
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We carried out ultrasonic measurements of the high temperature phase of Fe
3O
4 under two experimental conditions: (1) applying hydrostatic pressure up to 1.2 GPa and (2) controlling the magnetization direction. In the former experiment, the anomaly of C
44 wassuppressed by the application of pressure, while C
11 was enhanced. However, the normalized pressure dependence of C
11 and C
44 were the same. In the latter, C
11 showed dependence on the relative direction between the magnetization and the sound propagation.We found that the temperature dependence of the extraordinary part of both C
11 and C
44 is well explained by the existence of a deformation unit, which remains up to room temperature. In addition, the observed magnetization direction dependence of C
11suggests that the deformation of a unit depends on the relative direction between the main axis of a unit and the magnetization direction.
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Makoto Iwata, Hiroshi Orihara, Yoshihiro Ishibashi
Subject area: Equations of state, phase equilibria, and phase transitions.
1998 Volume 67 Issue 9 Pages
3130-3136
Published: September 01, 1998
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The linear and third-order nonlinear dielectric susceptibilities in the type-II incommensurate phase were investigated on the basis of the Landau-type thermodynamic potential. The expression for the frequency dependence of the third-order susceptibility in the incommensurate phase, for which the thermodynamic potential includes no Lifshitz invariant, was obtained. It was found that the third-order nonlinear susceptibility shows a jump with the change of its sign at the incommensurate transition point even in the second order transition, which is caused by the contribution from the amplitude mode of the modulated structure. We found that the third-order susceptibility reflects the behavior of the amplitude mode in the incommensurate phase. As a result, it has turned out that the measurement of third-order nonlinear dielectric susceptibility becomes a powerful method as a probe for the amplitude mode in the modulated structure.
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Kazuya Saito
Subject area: Equations of state, phase equilibria, and phase transitions.
1998 Volume 67 Issue 9 Pages
3137-3140
Published: September 01, 1998
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Effect of impurities on structural phase transition of displacive typewas examined through molecular dynamics simulation.Anharmonic oscillators were arranged on a two-dimensional square lattice with harmonic nearest-neighbor interaction.Local order parameters were calculated with impurities of different strength.Weak impurities affect more strongly than strong inpurities inrelative magnitude.
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Masaaki Geshi, Tatsuki Oda, Yasuaki Hiwatari
Subject area: Equations of state, phase equilibria, and phase transitions.
1998 Volume 67 Issue 9 Pages
3141-3146
Published: September 01, 1998
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We studied the structural phase transition of Se under highpressure by means of a full-potential linearized-augmented-plane-wavemethod. We calculated the electronic structure and the total energy at various volumes for the β-Po type rhombohedral and the bcc structure, from which we estimated the transition pressure. It was found that a first-order phase transition appears at a much lower pressure than the observed value with a small volume reduction.The structural properties calculated were discussed and compared with theavailable experimental data.
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Tomohiro Adachi, Ichiro Hatta, Hironobu Ikeda
Subject area: Thermal properties of condensed matter.
1998 Volume 67 Issue 9 Pages
3147-3150
Published: September 01, 1998
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The effects of halogenated alcohol on the phase transitions of dipalmitoylphosphatidylcholine (DPPC) were investigated. Differential scanning calorimetry (DSC) was used to study the gel-to-liquid-crystalline phase transitions. A biphasic behavior takes place in DPPC with halogenated alcohol. The transition temperature from the gel to a liquid-crystalline phase (T
m) decreases with increasing concentration of halogenated alcohol in aqueous solution. Above the threshold concentration, T
m increases with increasing the concentration in the solution. Except for bromopropanol, the transition temperature decreases again at a much higher concentration and a third-phase region is formed. The biphasic or triphasic behavior of DPPC with halogenated alcohol is as follows: bromoalcohol gives rise to a larger shift of T
m at the threshold concentration than chloroalcohol. The curvature of T
m at the threshold concentration was larger in the case of longer-chain halogenated alcohol.
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Katsurou Hanzawa
Subject area: Electron states in condensed matter.
1998 Volume 67 Issue 9 Pages
3151-3158
Published: September 01, 1998
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The intermediate-valence states of SmB
6 and SmSare described in terms of the periodic Anderson model comprised ofthe localized 4f multiplet states
6H
5/2 and
7F
0 oftwo adjacent configurations 4f
5 and 4f
6, the wide conduction band states represented by the plane wave functions, and the hybridizations between the 4f and the conduction states.We take hole picture and introduce fermi operators representingthe states of
6H
5/2 and a bose operator for the
7F
0 singlet for each Sm site.At low temperatures, the bosons form a condensate, and consequently the fermion states hybridize with the conduction-band statesto become itinerant, accompanied with an anisotropic gap structure. The susceptibility is dominated by the Van Vleck contribution fromthe excited
7F
1 level of 4f
6, while the
6H
5/2 states of 4f
5gives a small Pauli-type contribution, in good agreement with experimental results.
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Ken–ichi Hino
Subject area: Electron states in condensed matter.
1998 Volume 67 Issue 9 Pages
3159-3170
Published: September 01, 1998
Released on J-STAGE: October 01, 1999
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The adiabatic-expansion method is applied to problems for Wannier excitons in GaAs/Al
xGa
1-xAs quantum wells.Adiabatic-potential curves with respect to an exciton radius projectedonto the layer-plane are calculated and theadvantages and effectiveness of employing the present method are discussed.Bound-state energies are computed and compared with those of other references as illustrations.Further discussion is made on applicability of the method to the scattering problems for Fano-resonance states.
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Etsuji Yamamoto, Yoshinori Haga, Tetsuo Honma, Yoshihiko Inada, Dai Ao ...
Subject area: Electron states in condensed matter.
1998 Volume 67 Issue 9 Pages
3171-3175
Published: September 01, 1998
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We grew a single crystal of UB
2 with the hexagonal structure andobserved the de Haas-van Alphen (dHvA) oscillation.All of the dHvA branches, which are about seven in number, aredetected in the limited angle regions.They are well explained by the 5f-itinerant relativistic band theorywith an exchange and correlation potential in a local density approximation.Namely, UB
2 is a compensated metal with an equal number of electron and hole.The Fermi surface consists of two closed but corrugated Fermi surfaces.The cyclotron masses are moderately heavy, ranging from 1.2 to 7.7m
0.
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Hiroshi Yamagami
Subject area: Electron states in condensed matter.
1998 Volume 67 Issue 9 Pages
3176-3190
Published: September 01, 1998
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The linearized-augmented-plane-wave (LAPW) method isgeneralized to case of an all-electron fully-relativisticspin-polarized self-consistent band calculation based onthe relativistic spin-density functional theory.Inside spheres around nuclei, the Bloch function is expandedby spherical-symmetry bases and their energy-derivatives, each of which is solved by the corresponding spin-polarized coupledDirac equation (SPCDE) including a coupling of j =
l - 1/2 with j =
l + 1/2 partial state through the magnetic field.In the interstitial region, the relativistic plane waveis used as a conventional basis function.The core states inside the spheres are treated on the samefooting of the SPCDE in all iterative processes.This band theory is applied to BCC Fe, HCP Gd and uranium monochalcogenidesUS, USe and UTe as an interesting example of the ferromagnetic 3d, 4f and 5f systems, respectively. The electronic band structures are shown together with the spin and orbital moments.
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Jianyong Ouyang, Kyuya Yakushi, Yoji Misaki, Kazuyoshi Tanaka
Subject area: Electron states in condensed matter.
1998 Volume 67 Issue 9 Pages
3191-3198
Published: September 01, 1998
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Polarized reflectance spectra were measured on the conductive (010) plane of metallic (BDT-TTP)
2X (X=SbF
6, AsF
6) single crystals at room and low temperatures. Well-defined plasma edges appeared in both directions parallel (//a) and perpendicular (⊥ a) to the molecular stack, indicating two-dimensional band structures with a significant anisotropy. The intra- and inter-stack transfer integrals were estimated from the plasma frequencies in the framework of tight-binding model. Based on these transfer integrals, the energy dispersion, density of state, and Fermi surface were calculated. The Fermi surfaces of both compounds were open in the k
c direction. The temperature dependence of the transfer integrals was determined by analyzing the low-temperature spectra. The intra-stack transfer integral increased by about 30\ he enhancement of inter-stack transfer integral was very weak. So the system became more anisotropic at low temperatures. The strongly appeared CH stretching mode in the ⊥ a spectra suggested that the conjugated π -electrons were extended over the hydrogen atoms of BDT-TTP molecule.
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Yukitoshi Motome, Masatoshi Imada
Subject area: Electron states in condensed matter.
1998 Volume 67 Issue 9 Pages
3199-3215
Published: September 01, 1998
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Ground state properties of multi-orbital Hubbard models areinvestigated by the auxiliary field quantum Monte Carlo method.A Monte Carlo technique generalizedto the multi-orbital systems is introduced and examined in detail.The algorithm contains non-trivial cases wherethe negative sign problem does not exist.We investigate one-dimensional systemswith doubly degenerate orbitals by this new technique.Properties of the Mott insulating state are quantitativelyclarified as the strongly correlated insulator, where the charge gap amplitude is much larger than the spin gap.The insulator-metal transitions drivenby the chemical potential shows a universality classwith the correlation length exponent ν=1/2, which is consistent with the scaling arguments.Increasing level split between two orbitals drives crossoverfrom the Mott insulator with high spin state tothe band insulator with low spin state, where the spin gap amplitude increases and becomes closer to the charge gap.Experimental relevance of our resultsespecially to Haldane materials is discussed.
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Hiroshi Harashina, Hisashi Sasaki, Katsuaki Kodama, Masatoshi Sato, Sh ...
Subject area: Superconductivity.
1998 Volume 67 Issue 9 Pages
3216-3223
Published: September 01, 1998
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Neutron scattering studies on a c-axis polarized B
2u phonon havebeen carried out by using single crystals ofYBa
2Cu
3O
7, YBa
2Cu
3O
6.7 andYBa
2Cu
2.9Zn
0.1O
6.75.For YBa
2Cu
3O
7, sharp decreases in the energy and width ofthe phonon mode have been observed with decreasing temperature T at aroundthe superconducting transition temperature T
c.For the underdoped samples, the gradual downward deviations of thesequantities from the ordinary T-dependence begin far above T
cwith decreasing T, which is considered to be associated with the formationof the pseudo gap with the same symmetry as that of the superconducting orderparameter, i.e., the (x
2-y
2)-like one.These deviations become significant, with decreasing T, at temperatureshigher than the so-called spin-gap temperatureT
SG of YBa
2Cu
3O
6.7 (-- 150 K).Observed insensitive nature of the anomaly above T
c to theZn-doping can be explained by considering the wave vector (q)dependence of the pseudo gap and the coupling strength of the B
2umode to the gap, and also by considering that randomness effectsintroduced by the doping are more significant in the q-region withthe smaller energy gap.
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Masashi Yamashiro, Yukio Tanaka, Yasunari Tanuma, Satoshi Kashiwaya
Subject area: Superconductivity.
1998 Volume 67 Issue 9 Pages
3224-3233
Published: September 01, 1998
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Tunneling conductance spectra of normal metal/insulator/triplet superconductor junctions are investigated theoretically. As triplet paring states we select several types of symmetriesthat are promising candidatesfor the superconducting states in UPt
3 and in Sr
2RuO
4. The calculated conductance spectra aresensitive to the orientation of the junctionwhich reflects the anisotropy of the pairing states.They show either zero-bias conductance peaks or gap-like structures depending on the orientation of the junctions. The existence of a residual density of states, peculiar to nonunitarystates, is shown to have a significant influence on the properties of the conductance spectra.Present results serve as a guide for the experimental determination of the symmetry of the pair potentials in UPt
3 and Sr
2RuO
4.
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Fumiaki Hayashi, Eiji Ueda, Masatoshi Sato, Kenji Kurahashi, Kazuyoshi ...
Subject area: Superconductivity.
1998 Volume 67 Issue 9 Pages
3234-3239
Published: September 01, 1998
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STM/STS studies have been carried out on single crystals of the electron-doped high-T
c oxide Nd
2-xCe
xCuO
4 (x--0.15, T
c--20.5 K) to clarify the symmetry of its superconducting order parameter Δ. The observed gap structure of the quasi-particle excitation is found to depend on the distance between the tip and the sample surface and its characteristics indicate that the in-plane anisotropy of Δ is basically similar to that reported previously for hole-doped high-T
c oxides: It is, at first sight, xy-like but can be explained by the (x
2-y
2) symmetry by applyinga model proposed previously [J. Phys. Soc. Jpn. 64 (1995) 1476], which takes account of the electron wave vector dependenceof the tunneling probability.The zero bias conductance peak has also been observed.
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Keiji Itoh, Takeshi Usuki, Shigeru Tamaki
Subject area: Magnetic properties and materials.
1998 Volume 67 Issue 9 Pages
3240-3243
Published: September 01, 1998
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The magnetic susceptibility of the liquid In
1-xSe
x system have been measured as functions of concentration and temperature. The magnetic susceptibility of the system shows a broad diamagnetic maximum near x=0.58. This behaviour corresponds to the concentration variation of electronic conductivity reported previously and supports our previous suggestion of the valence fluctuation of In ions. By using the data of magnetic susceptibility with known electronic conductivity and thermoelectric power data, the density of state N(E) have been determined and the diamagnetic susceptibility due to ion core, χ
d, has also been obtained. The obtained value of χ
d suggests the occurrence of monovalent In ion near the composition x=0.58.
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Kiyohiro Sugiyama, Miho Nakashima, Yoshiyuki Yoshida, Yasushi Kimura, ...
Subject area: Magnetic properties and materials.
1998 Volume 67 Issue 9 Pages
3244-3250
Published: September 01, 1998
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We measured the electrical resistivity, specific heat, magnetic susceptibility and high-field magnetization in TbCu
2 with the orthorhombic structure.The metamagnetic transtion was found in a wide temperature range of 4.2 to 150 K for the magnetic field along the c-axis.This transition is similar to those of DyCu
2 and PrCu
2, which are due to the magnetic-axis conversion between easy (a-) and hard (c-) axes in magnetization.The metamagnetic transition was, however, not found in HoCu
2 with the same crystal structure and similar magnetic anisotropy.
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Takashi Ooshima, Masayasu Ishikawa
Subject area: Magnetic properties and materials.
1998 Volume 67 Issue 9 Pages
3251-3255
Published: September 01, 1998
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We have investigated low-temperature magnetic properties of Ce(Rh
1-xCo
x)
2Ge
2 (0≤ x≤ 1) by the measurements of the specific heat, the magnetic susceptibility and the magnetization, and obtained an anomalous magnetic phase diagram: CeRh
2Ge
2 exhibited two magnetic transitions at 14.5 and 8.9, K. Both transition temperatures almost linearly decrease with the Co substitution up to x-- 0.3 and finally disappear at x-- 0.75 following a little hump centered around x-- 0.5. This interesting phase diagram is discussed in the framework of Doniach's model.
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Teruhiko Akazawa, Takashi Suzuki, Hiroshi Goshima, Tomohiro Tahara, To ...
Subject area: Magnetic properties and materials.
1998 Volume 67 Issue 9 Pages
3256-3260
Published: September 01, 1998
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UNiSn undergoes a multiplex transition from a paramagnetic semiconductor (Phase I) to an antiferromagnetic metal with ferroquadrupolar order (Phase III) at T
N-- 43, K in zero field. We have measured elastic moduli, thermal expansion, magnetization and electrical resistivity of UNiSn in magnetic field. Magnetic field raises the quadrupole-ordering temperature T
Q, which was found to be identical to the semiconductor-metal transition temperature T
SM, while T
N is nearly field-independent. We observed a separation of T
N and T
Q in high magnetic field above -- 4, T, and we found a new phase (Phase II) between T
N and T
Q, which has been identified as a paramagnetic metal with ferroquadrupolar order. The coincidence of T
Q and T
SM strongly suggests that the ferroquadrupolar order is responsible for a change in electronic structure, leading to metallic conduction.
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