Journal of the Physical Society of Japan
Online ISSN : 1347-4073
Print ISSN : 0031-9015
ISSN-L : 0031-9015
Volume 74, Issue 12
Displaying 1-46 of 46 articles from this issue
  • Akinori Awazu
    2005 Volume 74 Issue 12 Pages 3127-3130
    Published: December 15, 2005
    Released on J-STAGE: February 07, 2008
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    The drift motions of particles in a nonequilibrium lattice gas system are investigated. We consider a system that consists of two particles interacting repulsively and the potential forces acting on these particles. When only one particle is driven by an external driving field, the other particle shows the following two types of drift motions on the average, depending on the field strength, under certain conditions: I) The particle drifts in the same direction as the external field (forward drift) if the external field is sufficiently strong. II) The particle drifts in the opposite direction to the external field (backward drift) if the external field is of a certain strength. We explain the mechanisms of this phenomenon by considering the transition diagrams.
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  • Akihito Ishizaki, Yoshitaka Tanimura
    2005 Volume 74 Issue 12 Pages 3131-3134
    Published: December 15, 2005
    Released on J-STAGE: February 07, 2008
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    Reduced equations of motion for a two-level system strongly coupled to a harmonic oscillators bath are constructed by extending the hierarchy of equations introduced by Tanimura and Kubo [J. Phys. Soc. Jpn. 58 (1989) 101]. The set of equations treats the bath in a nonperturbative manner and is applicable to a low-temperature system with taking into account the correlation time of noise. By numerically calculating linear absorption spectra for different temperatures, we demonstrate that the present theory is not afflicted with the dynamical positivity problem that occurs at low temperatures without the rotating wave approximation. Remarkable changes are found in the spectra when the temperature is lower than the resonant energy of the two-level system.
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  • Kazumasa Hattori
    2005 Volume 74 Issue 12 Pages 3135-3138
    Published: December 15, 2005
    Released on J-STAGE: February 07, 2008
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    A multipolar Kondo model of an impurity spin SI=3⁄2 interacting with conduction electrons with spin sc=3⁄2 is investigated using boundary conformal field theory. A two-channel Kondo (2CK)-like non-Fermi liquid (NFL) under the particle-hole symmetry is derived explicitly using a “superspin absorption” in the sector of a hidden symmetry, SO(5). We discuss the difference between the usual spin-1⁄2 2CK NFL fixed point and the present one. In particular, we find that, unlike the usual 2CK model, the low temperature impurity specific heat is proportional to temperature.
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  • Hiroaki Kusunose, Yoshio Kuramoto
    2005 Volume 74 Issue 12 Pages 3139-3142
    Published: December 15, 2005
    Released on J-STAGE: February 07, 2008
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    The azimuthal angle dependence observed in the resonant X-ray scattering in phase IV of Ce0.7La0.3B6 is analyzed theoretically. It is shown that the peculiar angle dependence observed in the E2 channel is consistent with the Γ5u-type octupole order with principal axis along [111] and equivalent directions. Under the assumption that the four equivalent octupole domains are nearly equally populated in the sample, the observed angle dependences are reproduced by calculation for both σσ′ and σπ′ polarizations. The calculation for various symmetries of order parameters unambiguously excludes order parameters other than the Γ5u-type octupole.
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  • Yasumasa Takagi, Yoshihide Yoshimoto, Kan Nakatsuji, Fumio Komori
    2005 Volume 74 Issue 12 Pages 3143-3146
    Published: December 15, 2005
    Released on J-STAGE: February 07, 2008
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    Nonlocal one-dimensional motions of a topological defect are induced by electron tunneling through the dangling-bond states on the clean Ge(001) surface using scanning tunneling microscopy below 80 K. The direction of the motion depends both on the energy of the carriers in the surface state and on the distance between the defect and the tunneling point. The results are interpreted using an electronic excitation model by hot carriers injected into the surface states. The critical distance of the motion is anisotropic and consistent with the band structure of the surface states.
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  • Hiroto Ohta, Chishiro Michioka, Yutaka Itoh, Kazuyoshi Yoshimura
    2005 Volume 74 Issue 12 Pages 3147-3150
    Published: December 15, 2005
    Released on J-STAGE: February 07, 2008
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    We succeeded in synthesizing powder samples of bilayer hydrate sodium cobalt oxide superconductors NaxCoO2·yH2O with Tc=0–4.6 K by systematically changing the duration in a 75% relative humidity atmosphere after intercalation of water molecules. From magnetic measurements, we found that a sample kept for one day in the atmosphere does not show any superconductivity down to 1.8 K, and that samples kept for 2–7 days show superconductivity, in which Tc increases up to 4.6 K with increasing duration. Tc and the superconducting volume fraction are almost invariant between 7-day and 1-month durations. The 59Co nuclear quadrupole resonance (NQR) spectra indicate a systematic change in the local charge distribution on the CoO2 plane with a change in duration.
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  • Makoto Isoda, Shigeyoshi Mori, Seiji Masuda
    2005 Volume 74 Issue 12 Pages 3151-3154
    Published: December 15, 2005
    Released on J-STAGE: February 07, 2008
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    The emergence of ferrimagnetism caused by the charge ordering of commensurately doped charged Ising spins is proposed in the extended Ising model, equivalent to the Blume–Emery–Griffiths model. The stability of the ferrimagnetic state is discussed on the basis of the energy at zero temperature, the sublattice magnetizations from mean field approximation, and Monte Carlo simulation, as examples on triangular and square lattices. The magnitude of the ferrimagnetic moment is suggested in connection with the dimensionality of the lattice.
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  • H. Kageyama, J. Yasuda, T. Kitano, K. Totsuka, Y. Narumi, M. Hagiwara, ...
    2005 Volume 74 Issue 12 Pages 3155-3158
    Published: December 15, 2005
    Released on J-STAGE: February 07, 2008
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    High-field magnetization measurements have been performed up to 56 T for a two-dimensional S=1⁄2 frustrated square-lattice antiferromagnet (CuCl)LaNb2O7, a recently discovered spin gap system (Δ⁄kB=26.7 K). It is found that the spin gap closes at a surprisingly low field Hc1=10.3 T compared with that expected from the zero-field spin gap (Δ⁄gμB=18.4 T). For H>Hc1, the magnetization exhibits a linear increase without any trace of anomalies such as fractional plateaus until it saturates at Hc2=30.1 T. This means that the gapless phase, where the field-induced magnetic ordering is expected to occur at low temperatures, is stable over a wide field region. These results suggest strong correlations of triplet excitations in the layer and the proximity of the spin-liquid phase to the magnetically ordered phase.
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  • Yuki Fuseya, Masahisa Tsuchiizu, Yoshikazu Suzumura, Claude Bourbonnai ...
    2005 Volume 74 Issue 12 Pages 3159-3162
    Published: December 15, 2005
    Released on J-STAGE: February 07, 2008
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    The temperature dependence of magnetic susceptibility, χ(T), is investigated for one-dimensional interacting electron systems at quarter filling within the Kadanoff–Wilson renormalization-group method. The forward scattering on the same branch (the g4-process) is examined together with the backward (g1) and forward (g2) scattering amplitudes on opposite branches. In connection with lattice models, we show that χ(T) is strongly enhanced by the nearest-neighbor interaction, an enhancement which surpasses that of the next-nearest-neighbor interaction. A connection between our predictions for χ(T) and experimental results for χ(T) in quasi-one-dimensional organic conductors is presented.
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  • Nariyuki Nakagiri, Kei-ichi Tainaka, Jin Yoshimura
    2005 Volume 74 Issue 12 Pages 3163-3166
    Published: December 15, 2005
    Released on J-STAGE: February 07, 2008
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    Habitat destruction is one of the primary causes of species extinction. In the present article, we apply bond and site destructions to a prey–predator system. Predator reproduction is disturbed by these destructions, while prey sustains no direct damage. It is found for both bond and site destructions that the number of predators increases in spite of the increase in destruction. However, if the destruction is too great, the predators decreases and eventually goes extinct. The mean-field theories for both type of destruction predict the same extinction threshold values. In contrast, the simulations for bond and site destructions reveal that extinction thresholds are much smaller than the mean-field theory predicts. This may be the result of the fragmentation of habitat via the percolation of habitat destruction.
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  • Masataka Iwao
    2005 Volume 74 Issue 12 Pages 3167-3178
    Published: December 15, 2005
    Released on J-STAGE: February 07, 2008
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    The method of the ultradiscrete limit is applied to a class of discrete Hamiltonian systems, where each discrete system, for some time shift, is satisfied by the general solution of a corresponding continuous Hamiltonian system parametrized with a lattice polygon. Each polar set of the lattice polygon gives a representation of the general solution of the ultradiscrete system.
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  • Ippei Danshita, Kyota Egawa, Nobuhiko Yokoshi, Susumu Kurihara
    2005 Volume 74 Issue 12 Pages 3179-3185
    Published: December 15, 2005
    Released on J-STAGE: February 07, 2008
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    We investigate collective excitations of Bose–Einstein condensates at absolute zero in a double-well trap. We solve the Bogoliubov equations with a double-well trap, and show that the crossover from the dipole mode to the Josephson plasma mode occurs in the lowest energy excitation. It is found that the anomalous tunneling property of low energy excitations is crucial to the crossover.
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  • Kouichi Okunishi
    2005 Volume 74 Issue 12 Pages 3186-3192
    Published: December 15, 2005
    Released on J-STAGE: February 07, 2008
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    We present a real-space renormalization group approach for the corner Hamiltonian, which is relevant to the reduced density matrix in the density matrix renormalization group. A set of self-consistent equations that the renormalized Hamiltonian should satisfy in the thermodynamic limit is also derived from the fixed point of the recursion relation for the corner Hamiltonian. We demonstrate the renormalization group algorithm for the S=1⁄2 XXZ spin chain and show that the results are consistent with the exact solution. We further examine the renormalization group for the S=1 Heisenberg spin chain and then discuss the nature of the eigenvalue spectrum of the corner Hamiltonian for the nonintegrable model.
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  • Satoshi Tsuge, Akiko Shimano, Yuko Tohyama, Emi Kayama, Satoshi Obara, ...
    2005 Volume 74 Issue 12 Pages 3193-3201
    Published: December 15, 2005
    Released on J-STAGE: February 07, 2008
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    Electron impact ionization of La, Pr, Ho, Tm, and Lu Atoms has been studied through measurements of absolute total (apparent σa and counting σc) and charge-separated partial cross sections σq+ (q=1–4) from the single ionization thresholds to 900 eV. The absolute and partial measurements were done using an electron–atom crossed beam apparatus and a magnetic deflection mass spectrometer, respectively. After a brief discussion on the present results, an overall discussion is made in more compact form on the cross-section results for 13 lanthanide-atom species including those for the 8 species treated in our previous studies. It is confirmed that the atoms having a 5d electron (La, Gd, and Lu) provide larger single-ionization cross sections and thereby larger σc values and larger population of singly-charged ions. It is also confirmed that resonance-like feature starting around the 4d limits is observed in the σ3+ curves for lighter lanthanide atoms. This phenomenon, observed for the first time for a neutral-atom series, is explained as the shape resonance occurring in the scattered-electron channel.
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  • Tomohiro Aoyama, Takashi Ishihara, Yukio Kaneda, Mitsuo Yokokawa, Ken& ...
    2005 Volume 74 Issue 12 Pages 3202-3212
    Published: December 15, 2005
    Released on J-STAGE: February 07, 2008
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    The statistics of energy transfer is studied by using the data of a series of high-resolution direct numerical simulations of incompressible homogeneous turbulence in a periodic box with the Taylor micro-scale Reynolds number Rλ and grid points up to approximately 1130 and 40963, respectively. The data show that the energy transfer T across the wave number k is highly intermittent and the skewness S and flatness F of T increase with k approximately as S∝(kL)αS, F∝(kL)αF in the inertial subrange, where αS∼2⁄3, αF∼1 and L the characteristic length scale of energy containing eddies. The comparison between the statistics of T, the energy dissipation rate ε and its average εr over a domain of scale r shows that T is less intermittent than ε, while there is a certain similarity between the probability distribution functions of T and εr.
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  • Kenji Maruyama, Hirohisa Endo, Hideoki Hoshino
    2005 Volume 74 Issue 12 Pages 3213-3220
    Published: December 15, 2005
    Released on J-STAGE: February 07, 2008
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    Extended X-ray absorption fine structure (EXAFS) and neutron diffraction measurements, and the detailed structural modeling by reverse Monte Carlo (RMC) simulation have been performed in order to study the short- and intermediate-range structures of liquid Rb–Se mixtures. The Se chains in the liquid mixture are strongly bent to form horseshoe-like Se chains with Rb atoms at the chain ends, creating a large amount of voids. The interaction between Rb and Se atoms is very weak and Rb atoms come close together. Near the boundary of the miscibility gap at low temperature the short Se chains link up to form a large cluster, and Rb atoms sit around it. The structure factor S(Q) in the liquid mixture has a small pre-peak at ∼1.3 Å−1. The computed partial Sij(Q) for the RMC model indicates that the pre-peak is associated with the Se–Se interchain component of S(Q). The voids in the structure play an important role in the appearance of the pre-peak in S(Q). From the void analysis using Delaunay tessellation it has been revealed that the observed pre-peak corresponds to a pre-peak in the concentration–concentration structure factor due to the chemically ordered packing of the voids and Se chains in the structure.
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  • Ching Tarng Liang, Klaus-Dieter Schotte
    2005 Volume 74 Issue 12 Pages 3221-3226
    Published: December 15, 2005
    Released on J-STAGE: February 07, 2008
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    It is shown that with a numerical analysis, based on band structure calculations, using standard local spin density approximations the structural details of K2CuF4 can be reproduced. We compare with Ishizuka et al.’s pressure dependence measured up to 14 GPa with synchrotron radiation. Corrections have to be made on the results of the local density calculations, however, like the “over-binding” which gives too small sizes for the lattice constants. Using the Wien code one can predict Jahn–Teller distortions in the low and in the high pressure phase of K2CuF4 in fair accord with the observation.
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  • S. Uma Maheswari, Hitose Nagara, Koichi Kusakabe, Naoshi Suzuki
    2005 Volume 74 Issue 12 Pages 3227-3235
    Published: December 15, 2005
    Released on J-STAGE: February 07, 2008
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    We present the calculations of the phonon frequency and its line width over the Brillouin zone for simple substances based on ab-initio linear response theory and the evaluation of superconducting transition temperature. The substances we report on are FCC iodine, FCC lithium, and BCC tellurium at high pressures. In iodine the phonon dispersion reveals a phonon softening along the Σ-line (Γ–K direction) near the lower pressure boundary of the FCC phase. In lithium, the frequency softening is striking along the entire Λ-line (Γ–L direction) and along the Σ-line (Γ–K direction) in the upper pressure boundary of the FCC phase. The FCC structure shows a phonon instability around 40 GPa and a turnover of the Tc before reaching this pressure. Similar phonon anomaly has been observed in BCC tellurium under high pressure. We discuss the origins of the soft phonon modes. The soft modes have much bigger line width than the other modes and contribute more to the electron phonon coupling constants. We have discussed the superconducting transition temperature on the basis of the Allen–Dynes formula, assuming phonon mediated superconductivity in those materials. The increasing phonon anomalies strongly dictate the direction of increasing Tc in these materials. Calculated values of Tc themselves show good agreement with experiments.
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  • T. Kanaya, K. Kakurai, I. Tsukushi, R. Inoue, H. Watanabe, M. Nishi, K ...
    2005 Volume 74 Issue 12 Pages 3236-3240
    Published: December 15, 2005
    Released on J-STAGE: February 07, 2008
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    We performed thermal neutron spin echo measurements on a glass-forming polymer, deuterated polybutadiene (–[CD2–CD=CD–CD2]n–; PB-d6), in a high Q range up to 3.5 Å−1 covering the first and second peaks of the structure factor S(Q), and evaluated the decay rate Γ(Q) of the coherent intermediate scattering function as a function of Q. In contrast to the previous experimental findings on the first peak of S(Q) at Q=1.5 Å−1, no ‘de Gennes’ type narrowing was observed on the second peak at Q=2.9 Å−1. This novel finding indicates that the narrowing is hidden by the distinct motions of the soft –CD2–CD2– and =CD–CD2– units and the self-motions of the rigid and soft units in the Q range around the second peak. The temperature dependence of the relaxation rate Γ(Q) suggests that in the high Q range beyond the first peak of S(Q) the conformational changes in a deutrated PB chain are mainly observed.
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  • Shunsuke Furukawa, Dai Ikeda, Kazumitsu Sakai
    2005 Volume 74 Issue 12 Pages 3241-3247
    Published: December 15, 2005
    Released on J-STAGE: February 07, 2008
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    Transport properties in the presence of magnetic fields are numerically studied for the spin-1/2 Heisenberg XXZ chain. The breakdown of the spin-reversal symmetry due to the magnetic field induces the magnetothermal effect. In analogy with the thermoelectric effect in electron systems, the thermomagnetic power (magnetic Seebeck coefficient) is provided, and is numerically evaluated by the exact diagonalization for wide ranges of temperatures and various magnetic fields. For the antiferromagnetic regime, we find the magnetic Seebeck coefficient changes sign at certain temperatures, which is interpreted as an effect of strong correlations. We also compute the thermomagnetic figure of merit determining the efficiency of the thermomagnetic devices for cooling or power generation.
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  • Michikazu Kobayashi, Makoto Tsubota
    2005 Volume 74 Issue 12 Pages 3248-3258
    Published: December 15, 2005
    Released on J-STAGE: February 07, 2008
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    There is a growing interest in the relation between classical turbulence and quantum turbulence. Classical turbulence arises from complicated dynamics of eddies in a classical fluid. In contrast, quantum turbulence consists of a tangle of stable topological defects called quantized vortices, and thus quantum turbulence provides a simpler prototype of turbulence than classical turbulence. In this paper, we investigate the dynamics and statistics of quantized vortices in quantum turbulence by numerically solving a modified Gross–Pitaevskii equation. First, to make decaying turbulence, we introduce a dissipation term that works only at scales below the healing length. Second, to obtain steady turbulence through the balance between injection and decay, we add energy injection at large scales. The energy spectrum is quantitatively consistent with the Kolmogorov law in both decaying and steady turbulence. Consequently, this is the first study that confirms the inertial range of quantum turbulence.
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  • Masami Tsubota, Fumitoshi Iga, Kazuyuki Uchihira, Toshihiro Nakano, So ...
    2005 Volume 74 Issue 12 Pages 3259-3266
    Published: December 15, 2005
    Released on J-STAGE: February 07, 2008
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    We have studied the orbitally ordered states in Y1−xCaxTiO3 (0<x≤0.75) by resonant X-ray scattering (RXS) near the Ti K-edge (E∼5 keV) and by powder X-ray diffraction measurements. The RXS intensities at the 1s→4p transition energy (main-edge) gradually decrease with increasing x and remain finite even in the metallic phase for x>0.4. In contrast, the intensities at the 1s→3d transition energy (pre-edge) decrease rapidly with increasing x up to 0.15 and disappear at x∼0.4. The x dependences of the Jahn–Teller distortion is consistent with those of the RXS intensities at pre-edge. Namely, the RXS intensity at the pre-edge energy reflects the orbital ordered state. From our results, we conclude that the magnetic order in Y1−xCaxTiO3 becomes unstable at x∼0.15 when the orbital order is weakened, and the metallic phase appears in x>0.4 when the order of orbitals melts.
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  • Ryousuke Shiina
    2005 Volume 74 Issue 12 Pages 3267-3275
    Published: December 15, 2005
    Released on J-STAGE: February 07, 2008
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    A generalized periodic Anderson model with stable f2 configuration is examined through a Gutzwiller-type variational method (GM). In particular, we focus on the effect of the f2 crystal-field (CF) level scheme with singlet ground and triplet low-lying excited states. It is demonstrated that valence fluctuation from the f2 states is slightly enhanced by a small singlet–triplet CF splitting whereas it becomes strongly suppressed as the splitting increases. The GM predicts that this valence change caused by the CF is discontinuous in the case of small hybridization. The influence of the CF on magnetic properties is studied in terms of the Landau parameter of magnetic susceptibility.
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  • Tatsuma D. Matsuda, Yoshinori Haga, Shugo Ikeda, Hiroaki Shishido, Rik ...
    2005 Volume 74 Issue 12 Pages 3276-3282
    Published: December 15, 2005
    Released on J-STAGE: February 07, 2008
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    We have succeeded in growing a high-quality single crystal of ThIn3 with the cubic structure by the In-flux method and measured the electrical resistivity, magnetic susceptibility and de Haas–van Alphen (dHvA) effect. Several dHvA branches were observed, ranging from 5.2×106 to 1.7×108 Oe. The Fermi surface consists of a nearly spherical Fermi surface and a multiply-connected Fermi surface. The corresponding cyclotron effective masses are small, ranging from 0.31 to 1.4 m0. These Fermi surface properties are well explained by the energy band calculations based on the FLAPW method.
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  • Yasuhiro Tanaka, Masao Ogata
    2005 Volume 74 Issue 12 Pages 3283-3287
    Published: December 15, 2005
    Released on J-STAGE: February 07, 2008
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    The effects of charge ordering on the spin degrees of freedom is studied by using one-dimensional extended Hubbard model. The ground state property is investigated in the U→∞ limit using spin-charge factorized wave function. The effective exchange coupling Jeff and spin susceptibility χ are calculated as a function of nearest neighbor Coulomb interaction V for several electron densities. It is found that Jeff is suppressed by the effect of V through charge fluctuation and, as a result, χ increases with increasing V. Furthermore, χ at T=0 has no detectable anomaly at the transition point where a charge ordering occurs, because of the Berezinskii–Kosterlitz–Thouless (BKT) type transition of charge ordering. We also calculate χ by exact diagonalization on small clusters in realistic parameter range and obtained qualitatively the same results. These results mean that the charge fluctuation play important roles around the transition point and the charge ordering has little effect on the spin degrees of freedom. The relevance to experiments on (DI-DCNQI)2Ag is briefly discussed.
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  • Ko Furukawa, Toshifumi Hara, Toshikazu Nakamura
    2005 Volume 74 Issue 12 Pages 3288-3294
    Published: December 15, 2005
    Released on J-STAGE: February 07, 2008
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    ESR, NMR and X-ray measurements were performed for pristine and fully perdeuterio-TMTTF, TMTTF-d12 salts. Significant enhancement by deuteration of the charge-order phase transition temperature, TCO, was observed in ESR measurements for all (TMTTF)2X salts measured. No obvious relation between the SbF6 anion motion and the TMTTF charge-order was found by 19F NMR. We also performed single crystal X-ray measurements to understand the deuteration effects and temperature dependence of the crystal structure. A possible relationship between the TCO’s and crystallographical parameters is proposed. The deuteration effects and possible origin of the charge-ordering transition of TMTTF salts are discussed.
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  • Motoki Endo, Noriaki Kimura, Haruyoshi Aoki
    2005 Volume 74 Issue 12 Pages 3295-3305
    Published: December 15, 2005
    Released on J-STAGE: February 07, 2008
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    We have studied the dHvA effect in CeIn3 with particular attention to magnetic filed and spin dependences of the effective mass. We have observed several new frequency branches with effective masses up to 52m0. The results are discussed in comparison with those of LaIn3 and the band structure calculations based on localized f electron model. The effective mass of d oscillation is found to depend on magnetic field as well as on the direction of spin of the conduction electrons. The difference in the effective masses between the up and down spin electrons is larger for fields parallel to [001] and [111] than [110]. The difference is attributed to the characters of the orbits.
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  • Kazumasa Hattori, Yosuke Hirayama, Kazumasa Miyake
    2005 Volume 74 Issue 12 Pages 3306-3313
    Published: December 15, 2005
    Released on J-STAGE: February 07, 2008
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    An impurity four-level Kondo model, in which an ion is tunneling among 4-stable points and interacting with surrounding conduction electrons, is investigated using both perturbative and numerical renormalization group methods. The results of numerical renormalization group studies show that it is possible to construct the ground state wavefunction including the excited ion states if we take into account the interaction between the conduction electrons and the ion. The resultant effective mass of quasiparticles is moderately enhanced. This result offers a good explanation for the enhanced and magnetically robust Sommerfeld coefficient observed in SmOs4Sb12, some other filled-skutterudites, and clathrate compounds.
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  • Sota Ukai, Hiroshi Ito, Kazuhiro Marumoto, Shin-ichi Kuroda
    2005 Volume 74 Issue 12 Pages 3314-3319
    Published: December 15, 2005
    Released on J-STAGE: February 07, 2008
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    The electrical conduction of regioregular poly(3-hexylthiophene) (RR-P3HT) and regiorandom poly(3-hexylthiophene) (RRa-P3HT) doped with iodine is studied as a function of doping level. The electrical conductivity shows the thermally-activated behavior at low doping levels below 10% for RR-P3HT and 18% for RRa-P3HT. At high doping levels higher than 10% for RR-P3HT and 20% for RRa-P3HT, the electrical conductivity shows the three-dimensional variable-range hopping. The change in the conduction mechanism is explained qualitatively in terms of the growth of the density of states at the Fermi level and the dimensional crossover of the conduction path. The difference in the doping levels where the change occurs in RR-P3HT and RRa-P3HT is understood in terms of the carrier localization length, that is, the spatial extent of polaronic excitations in these polymers.
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  • Nguyen Van Hieu, Hiroaki Shishido, Arumugam Thamizhavel, Rikio Settai, ...
    2005 Volume 74 Issue 12 Pages 3320-3328
    Published: December 15, 2005
    Released on J-STAGE: February 07, 2008
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    We grew single crystals of PrCoIn5, PrRhIn5, and PrIrIn5 with the tetragonal crystal structure and measured the electrical resistivity, specific heat, magnetic susceptibility, magnetization and de Haas–van Alphen effect. These Pr compounds reveal no magnetic ordering. The topology of the Fermi surfaces is the same as that of a non-4f reference compound LaRhIn5. The cyclotron mass and/or the electronic specific heat coefficient are also approximately the same as those of LaRhIn5. The magnetic susceptibility and magnetization are anisotropic, reflecting the crystal structure, which are well explained by the tetragonal crystalline electric field scheme with the singlet ground state.
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  • Tetsuya Sasakawa, Kaori Mine, Keisuke Shigetoh, Toshiro Takabatake
    2005 Volume 74 Issue 12 Pages 3329-3333
    Published: December 15, 2005
    Released on J-STAGE: February 07, 2008
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    Magnetic, transport and specific-heat measurements of Ce1−xLaxRhAs (x≤0.1) have been performed. The host compound CeRhAs undergoes successive phase transitions with formation of superlattices at T1=360, T2=235, and T3=165 K, respectively. The transitions at T1 and T3 are associated with the formation of a wide gap of Eg1kB=2200 K and a narrow one of Eg2kB=310 K, respectively. All anomalies at T1, which are a jump in the specific heat C, a drop in the magnetic susceptibility χ and the activation-type behavior in the Hall coefficient, remain until x is increased up to 0.10, at which T1 is depressed to 297 K. These observations indicate that both the phase transition at T1 and the gap of Eg1 remain up to x=0.10. Anomalies in C and χ at T2 and T3, on the other hand, vanish at a small concentration x=0.01. The semiconducting behavior in both the electrical resistivity and thermopower below T3 also disappears at x=0.02. These facts corroborate that the narrow gap of Eg2 is quenched when the phase transition at T3 disappears. The distinct effects on the phase transitions in Ce1−xLaxRhAs and CeRhAs1−ySby indicate that coherent hybridization between Rh 4d and As 4p states is important for the formation of Eg1 below T1.
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  • Hiroshi Ito, Masaki Hanada, Hisaaki Tanaka, Shin-ichi Kuroda, Minoru M ...
    2005 Volume 74 Issue 12 Pages 3334-3339
    Published: December 15, 2005
    Released on J-STAGE: February 07, 2008
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    Resistivity anisotropy between parallel and perpendicular direction to the one-dimensional chain (ρ⁄ρ||) is measured for the quasi-one-dimensional iodo-bridged diplatinum complex (MMX-chains) Pt2(n-butylCS2)4I between 100–360 K. In order to measure the resistivity anisotropy of one single crystal in one thermal process, we used a method with six terminals of the geometry proposed by Safar et al. and Aouaroun et al. In the highly conductive semiconductive phase with the average valence (AV) state above 213 K, the resistivity anisotropy is as high as 104 and is almost temperature-independent. No anisotropy change is observed at the phase transition at 323 K, at which the valence of Pt does not change. At the phase transition to the low temperature alternate-charge-polarization (ACP) state at 210 K, the resistivity anisotropy abruptly decreases down to 103. In the ACP state, the resistivity anisotropy further decreases with lowewing the temperature. The difference in the behavior of the resistivity anisotopy in the two valence states indicates that the different conduction mechanisms dominates in each state.
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  • Fusayoshi J. Ohkawa
    2005 Volume 74 Issue 12 Pages 3340-3350
    Published: December 15, 2005
    Released on J-STAGE: February 07, 2008
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    A Kondo-lattice theory is applied to the tJ model on a quasi-two dimensional lattice. The Kondo temperature TK or kBTK is defined as an energy scale of local quantum spin fluctuations, with kB the Boltzmann constant. The bandwidth W* of quasiparticles, which is approximately given by W*\\simeq4kBTK, is renormalized by the Fock-type term of the superexchange interaction. When the lifetime width γ of quasiparticles is so small and temperature T is so low that γ⁄W*\\lesssim1 and kBTW*\\lesssim1, the renormalization is large. Even in the limit of the half filling, for example, the bandwidth W* is nonzero and of the order of |J|, with J the superexchange interaction constant between nearest neighbors. The Kondo temperature kBTK, which also gives a measure of the strength of the quenching of magnetic moments by local quantum spin fluctuations, increases away from the half filling; it is smaller for larger γ. Therefore, local-moment magnetism, which is characterized by TN>>TK, with TN the Néel temperature, appears for almost half fillings, and itinerant-electron magnetism, which is characterized by TN\\lesssimTK, appears for fillings away from the half filling; TN is higher for larger γ. The antiferromagnetic region as a function of electron fillings is wider for larger γ; this result implies that it is wider in more disordered systems than it is in less disordered ones. The difference or asymmetry of disorder between electron-doped and hole-doped cuprate oxide superconductors must be, at least partly, responsible for that of antiferromagnetic phases between them.
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  • Youichi Yanase, Masahito Mochizuki, Masao Ogata
    2005 Volume 74 Issue 12 Pages 3351-3364
    Published: December 15, 2005
    Released on J-STAGE: February 07, 2008
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    The possibility of multiple phase diagram in the novel superconductor NaxCoO2·yH2O is analyzed on the basis of the multi-orbital Hubbard model including the atomic spin–orbit coupling. We have shown that the spin triplet pairing state is stable in this model. The p-wave (f-wave) state is stabilized when the Hund’s rule coupling is large (small). In the precedent paper, we have determined the direction of d-vector at T=Tc and H=0 within the linearized Dyson–Gorkov equation. In this paper, the pairing state below Tc and under the magnetic field is determined within the weak coupling approximation including the paramagnetic effect. We find that the p+f coexistent state is stabilized at low temperatures in a part of parameter range. We point out that the phase diagram in the HT plane is quite different between the p-wave, f-wave and p+f-wave superconductivities. The characteristics of each phase are clarified by showing the magnetic susceptibility and specific heat. We discuss the comparison with experimental results and suggest some future experiments to detect the multiple phase transition.
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  • Seiya Haraguchi, Tomoyuki Naito, Hideo Iwasaki
    2005 Volume 74 Issue 12 Pages 3365-3369
    Published: December 15, 2005
    Released on J-STAGE: February 07, 2008
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    In-plane anisotropy of the resistivity and phase transition of the Josephson-vortex system have been studied in YBCO crystals with different oxygen-contents. Angular dependences of the resistivity are represented by superposition of four-fold anisotropy with a sharps dip for H||a- and b-axes and two-fold one in under-doped and over-doped crystals. Only two-fold in-plane anisotropy appears in optimally-doped ones. The anisotropic behaviors are described by the superconducting fluctuation and the Josephson-vortex pinning effect. The resistive transition for H||a- and b-axes shows sharp drop to zero resistivity accompanied with the first-order phase transition in the optimally-doped crystals. It is characterized by the second-order vortex-glass transition in over-doped and under-doped ones. It is indicated that the Josephson-vortex pinning is important in the determination of the in-plane anisotropy of the resistivity and the phase transition.
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  • Yusuke Nakai, Kenji Ishida, Daisuke Kikuchi, Hitoshi Sugawara, Hideyuk ...
    2005 Volume 74 Issue 12 Pages 3370-3374
    Published: December 15, 2005
    Released on J-STAGE: February 07, 2008
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    We have performed 139La,31P-NMR studies on a filled skutterudite superconductor LaFe4P12 with the critical temperature Tc=4.1 K. In the normal state, the presence of antiferromagnetic (AFM) fluctuations at finite wave vectors is suggested from the relation between the nuclear spin-lattice relaxation rate 1⁄T1 and the Knight shift. In the superconducting (SC) state, the distinct coherence peak is observed just below Tc, and is easily suppressed by applied fields. An exponential decrease of 1⁄T1 is observed, suggestive of the isotropic SC gap with 2Δ⁄(kBTc)=3.8. Besides, we observed the decrease of the Knight shift, indicative of the singlet-pair formation below Tc. These results are clear evidence that LaFe4P12 is a rare s-wave superconductor with significant AFM fluctuations.
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  • Jun’ichiro Hara
    2005 Volume 74 Issue 12 Pages 3375-3381
    Published: December 15, 2005
    Released on J-STAGE: February 07, 2008
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    Boundary conditions for the quasi-classical Green’s function at rough surfaces are studied on the basis of the thin dirty layer model. We construct a formal solution of the quasi-classical Green’s function in semi-infinite superconductors with rough surface which is simulated by a specular wall coated by a thin layer containing random impurities. Using the current conservation in the thin dirty layer, we propose a new boundary condition for the quasi-classical Green’s function at rough surfaces, which is available to treat rough surface effects from the diffusive limit to the specular limit. It is shown that our boundary condition is equivalent to the Ovchinnikov boundary condition and the random S-matrix model in the diffusive limit.
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  • Kaihei Ido, Aya Tobo, Koji Kaneko, Kenji Ohoyama, Hideya Onodera
    2005 Volume 74 Issue 12 Pages 3382-3386
    Published: December 15, 2005
    Released on J-STAGE: February 07, 2008
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    The field-direction dependence of the magnetic phase diagram was examined for the compound TbB2C2 with field-induced antiferroquadrupolar-ordering, in order to elucidate anisotropy in the magnetic phase diagrams for H||[100] and H||[110]. The field-induced phase for H||[100] (phase III), which is a phase in which antiferromagnetic (AFM) and antiferroquadrupolar (AFQ) orders coexist, seems to change continuously into the other (AFQ + AFM) phase (phase II) for H||[110]. The result implies that both III and II phases have some similarity in their magnetic structures or they are possibly the same as each other.
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  • Masao Nakamura, Makoto Izumi, Kenjiro Miyano
    2005 Volume 74 Issue 12 Pages 3387-3390
    Published: December 15, 2005
    Released on J-STAGE: February 07, 2008
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    We have investigated the effect of Jahn–Teller-type distortion in manganite thin films with finely controlled lattice distortion by exploiting epitaxial strain effect and tuning A-site ionic radius. The magnetic and transport properties of these films indicate the existence of the dimensional crossover in conduction as the lattice distortion changes. We also found a universal relationship between magnetization and resistivity irrespective of the sample compositions.
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  • Yousuke Takeuchi, Hiroyuki Mori
    2005 Volume 74 Issue 12 Pages 3391-3392
    Published: December 15, 2005
    Released on J-STAGE: February 07, 2008
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  • Taiki Ueda, Miho Nakashima, Masato Hedo, Yoshiya Uwatoko, Hiroshi Naka ...
    2005 Volume 74 Issue 12 Pages 3393-3394
    Published: December 15, 2005
    Released on J-STAGE: February 07, 2008
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  • Chihiro Sekine, Yosuke Shimaya, Ichimin Shirotani, Pierre Haen
    2005 Volume 74 Issue 12 Pages 3395-3396
    Published: December 15, 2005
    Released on J-STAGE: February 07, 2008
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  • Takafumi Kita
    2005 Volume 74 Issue 12 Pages 3397
    Published: December 15, 2005
    Released on J-STAGE: February 07, 2008
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  • Taka H. Nishino, Hisao Hayakawa
    2005 Volume 74 Issue 12 Pages 3398
    Published: December 15, 2005
    Released on J-STAGE: February 07, 2008
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  • Zenji Hiroi, Shigeki Yonezawa, Yuji Muraoka
    2005 Volume 74 Issue 12 Pages 3399
    Published: December 15, 2005
    Released on J-STAGE: February 07, 2008
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  • Zenji Hiroi, Shigeki Yonezawa, Jun-Ichi Yamaura, Takaki Muramatsu, Yos ...
    2005 Volume 74 Issue 12 Pages 3400
    Published: December 15, 2005
    Released on J-STAGE: February 07, 2008
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