Journal of the Physical Society of Japan
Online ISSN : 1347-4073
Print ISSN : 0031-9015
ISSN-L : 0031-9015
Volume 74, Issue 10
Displaying 1-42 of 42 articles from this issue
  • Katsuhiro Nakamura, Naofumi Nakazono, Taro Ando
    2005 Volume 74 Issue 10 Pages 2647-2650
    Published: October 15, 2005
    Released on J-STAGE: February 07, 2008
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    Using the nonlinear Schrödinger equation (Gross–Pitaevskii equation), the dynamics of a macroscopic wave packet for Bose–Einstein condensates falling through double slits is analyzed. This problem is identified with a search for the fate of a soliton showing a head-on collision with a hard-walled obstacle of finite size. We explore the splitting of the wave packet and its reorganization to form an interference pattern. Particular attention is paid to the role of gravity (g) and repulsive nonlinearity (u0) in the fringe pattern. The peak-to-peak distance in the fringe pattern and the number of interference peaks are found to be proportional to g−1⁄2 and u01⁄2g1⁄4, respectively. We suggest a way of designing an experiment under controlled gravity and nonlinearity.
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  • Katsuyoshi Matsushita, Ryoko Sugano, Akiyoshi Kuroda, Yusuke Tomita, H ...
    2005 Volume 74 Issue 10 Pages 2651-2654
    Published: October 15, 2005
    Released on J-STAGE: February 07, 2008
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    By molecular dynamics simulation, we have investigated classical Heisenberg spins, which are arrayed on a finite simple cubic lattice and interact with each other only by the dipole–dipole interaction, and have found its peculiar from-edge-to-interior freezing process. As the temperature is decreased, spins on each edge predominantly start to freeze in a ferromagnetic alignment parallel to the edge around the corresponding bulk transition temperature, then from each edge grow domains with short-ranged orders similar to the corresponding bulk orders, and finally the system is expected to end up with a unique multidomain ground state at the lowest temperature. We infer that these freezing characteristics are attributed to the anisotropic and long-range nature of the dipole–dipole interaction combined with a finite-size effect.
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  • Taka H. Nishino, Hisao Hayakawa
    2005 Volume 74 Issue 10 Pages 2655-2658
    Published: October 15, 2005
    Released on J-STAGE: February 07, 2008
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    From the molecular dynamics simulation of a system of hard-core disks in which an equilibrium cell is connected with a nonequilibrium cell, it is confirmed that the pressure difference between two cells depends on the direction of the heat flux. From the boundary layer analysis, the velocity distribution function in the boundary layer is obtained. The agreement between the theoretical result and the numerical result is fairly good.
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  • Yoji Ohashi
    2005 Volume 74 Issue 10 Pages 2659-2662
    Published: October 15, 2005
    Released on J-STAGE: February 07, 2008
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    We investigate the effective interaction between Cooper-pair molecules in the strong-coupling BEC regime of a superfluid Fermi gas with a Feshbach resonance. Our work uses a path integral formulation and a renormalization group (RG) analysis of fluctuations in a single-channel model. We show that a physical cutoff energy ωc originating from the finite molecular binding energy is the key to understanding the interaction between molecules in the BEC regime. Our work thus clarifies recent results by showing that aM=2aF is a bare molecular scattering length while aM=(0.6–0.75)aF is the low-energy molecular scattering length renormalized to include high-energy scattering up to ωc (here, aF is the scattering length between Fermi atoms). We also include many-body effects at finite temperatures. We find that aM is strongly dependent on temperature, vanishing at Tc, consistent with the earlier Bose gas results of Bijlsma and Stoof.
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  • Hisashi Mitani, Seigi Mizuno, Hiroshi Tochihara, Tohru Hayashi
    2005 Volume 74 Issue 10 Pages 2663-2666
    Published: October 15, 2005
    Released on J-STAGE: February 07, 2008
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    The coverage dependence of arced streak intensities observed in LEED pattern, for Li on Cu(001) surface at low coverage, (0–0.50), is studied theoretically. The streaks essentially originate from the deviation of numbers of adatoms on sublattice sites. In a lattice gas adsorption model, we can see two sublattices in terms of a phase on a wave number ky=2π⁄2a, which corresponds to the streaks. Then we calculate an expectation value for the deviation of numbers of adatoms on the two sublattice sites, for a given coverage. This deviation brings an atomic density wave and also gives an intensity of the streak. The calculated coverage dependence of the intensity is similar to the experiment. In the real experimental system, the streaks are expanded and deformed in diffraction space. It means inclined or incommensurate atomic density wave. Even in such a case, we show that the above two sublattice model is essentially sufficient.
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  • Shinji Uemura, Gaku Motoyama, Yasukage Oda, Takashi Nishioka, Noriaki ...
    2005 Volume 74 Issue 10 Pages 2667-2670
    Published: October 15, 2005
    Released on J-STAGE: February 07, 2008
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    We present a pressure-temperature phase diagram of URu2Si2 consisting of four states; i.e., a superconducting state, a hidden ordered (HO) state, a large-moment antiferromagnetically (LMAF) ordered state induced under pressure, and a ferromagnetic state that is presumably due to crystal imperfections. Our major observation is that the superconductivity does not coexist with the LMAF state. Provided that the ferromagnetism is associated with a tiny-moment antiferromagnetically ordered state, we argue that the hidden order parameter has a different symmetry from that of the antiferromagnetic states, which implies that there is no critical end point in a first-order phase line separating HO from LMAF in the phase diagram.
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  • Nobuya Maeshima, Kenji Yonemitsu
    2005 Volume 74 Issue 10 Pages 2671-2674
    Published: October 15, 2005
    Released on J-STAGE: February 07, 2008
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    We study photoinduced optical responses of one-dimensional strongly correlated electron systems. Optical conductivity spectra are calculated for the ground and photoexcited states in a one-dimensional Hubbard model at half filling by the exact diagonalization method. It is found that, in the Mott insulator phase, the photoexcited state has large spectral weights including the Drude weight below the optical gap. As a consequence, the spectral weight above the optical gap is markedly reduced. These results imply that a metallic state is induced by photoexcitation. A comparison between the photoexcited and hole-doped states shows that photoexcitation is similar to chemical doping.
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  • A. Harada, S. Kawasaki, H. Kotegawa, Y. Kitaoka, Y. Haga, E. Yamamoto, ...
    2005 Volume 74 Issue 10 Pages 2675-2678
    Published: October 15, 2005
    Released on J-STAGE: February 07, 2008
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    We report on a cooperative phenomenon of ferromagnetism and unconventional superconductivity (SC) in UGe2 through the measurements of 73Ge nuclear-quadrupole-resonance (NQR) under pressure (P). The NQR spectra evidenced phase separation into ferromagnetic and paramagnetic phases in the vicinity of Pc∼1.5 GPa, pointing to a first-order transition. The measurements of nuclear-spin–lattice-relaxation-rate 1⁄T1 revealed that SC emerges under the background of ferromagnetism, but not of the paramagnetic phase.
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  • Kengo Hoshihara, Kazumasa Miyake
    2005 Volume 74 Issue 10 Pages 2679-2682
    Published: October 15, 2005
    Released on J-STAGE: February 07, 2008
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    The microscopic origin of triplet superconductivity in Sr2RuO4 is discussed, paying attention to the role of Coulomb interaction, Upp, at the O site. It is shown on the dp model that Upp induces a ferromagnetic exchange interaction between “d-electrons” (molecular orbital with dxy-symmetry) at adjacent Ru sites, leading to short-range ferromagnetic correlations and promoting Cooper pairing with (sinpx±isinpy)-symmetry on the γ-band. The reason why such ferromagnetic correlations work effectively may be traced back to the fact that the level of 4d-electrons at Ru sites is relatively low and located near that of 2p-electrons at O sites.
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  • Yuji Inagaki, Atsushi Kobayashi, Takayuki Asano, Takuo Sakon, Hiroshi ...
    2005 Volume 74 Issue 10 Pages 2683-2686
    Published: October 15, 2005
    Released on J-STAGE: February 07, 2008
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    The ground-state properties of an S=1⁄2 quasi-one-dimensional quantum spin system (CH3)2NH2CuCl3 were investigated by X-ray structure analyses and high-field magnetization measurements. X-ray studies confirmed that the structural phase transition from monoclinic to triclinic phases occurs between 300 and 200 K. The magnetic chain realized at low temperatures involves three types of chlorine-bridged pathways that result in bond alternation with n=4, where n is the period of the spatial structure. High-field magnetization measurements at the lowest temperature of 0.5 K revealed a unique magnetization process with an initial rapid increase in a low field and a relatively gradual increase in a high field, separated by the magnetization plateau with half of the saturation moment. On the basis of these experimental facts, a novel quantum chain model, which is characterized by the alternation of an S=1 triplet dimer and an S=0 singlet dimer is proposed for the ground state of the present system.
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  • Akiko Kikkawa, Koichi Katsumata, Zentaro Honda, Koji Yamada
    2005 Volume 74 Issue 10 Pages 2687-2690
    Published: October 15, 2005
    Released on J-STAGE: February 07, 2008
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    Magnetic susceptibility, magnetization and heat capacity measurements are made on a single crystal sample of a spin–ladder material, Na2Fe2(C2O4)3(H2O)2. The susceptibilities show a broad maximum at a temperature of about 25 K and 20 K parallel (χ||) and perpendicular (χ) to the ladder direction, respectively. The maximum value of χ|| is about three times larger than that of χ. Both χ|| and χ decrease steeply at low temperatures down to about 5 K, at which χ|| shows an upturn. We find a broad peak in the temperature dependence of the heat capacity. Susceptibility, magnetization and heat capacity data are used to construct the magnetic field versus temperature phase diagram of this compound. Quantum fluctuations are not strong enough to form a singlet ground-state, probably due to the presence of Ising anisotropy. The actual ground state is expected to be close to the quantum critical-point between the spin-gapped and a Néel ordered phases with the help of the inter-ladder interaction.
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  • Masafumi Sera, Shinya Goto, Tatsurou Koshikawa, Moo-Sung Kim, Hideki T ...
    2005 Volume 74 Issue 10 Pages 2691-2694
    Published: October 15, 2005
    Released on J-STAGE: February 07, 2008
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    We have studied the magnetization, electrical resistivity and magnetic phase diagram of PrxLa1−xB6. The x dependence of the incommensurate (IC) magnetic ordering temperature, TIC1, is similar to that of NdxLa1−xB6. The noncollinear commensurate magnetic ordering is rapidly suppressed by La doping. These suggest that the IC magnetic ordering originates from the long-range RKKY-type exchange interaction and that the short-range Oxy-type AFQ interaction, which is easily affected by the local disturbance, is associated with the formation of the commensurate magnetic ordering in the C phase. The magnetic phase diagram of Pr0.8La0.2B6 is very different from those of PrB6 and Pr0.9La0.1B6. Although there exists the C and IC1 phases at H=0 in the latter two compounds, there exists only the IC1 phase at H=0 in Pr0.8La0.2B6. However, the C phase appears above 6 T only for H||⟨111⟩. The unusual magnetic phase diagram for H||⟨111⟩ is explained as a result of the competition between the exchange, quadrupolar and Zeeman interactions by taking into account the domain distribution, that depends on the applied magnetic field direction.
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  • Hideki Tou, Masahiro Doi, Masafumi Sera, Mamoru Yogi, Hitoshi Sugawara ...
    2005 Volume 74 Issue 10 Pages 2695-2698
    Published: October 15, 2005
    Released on J-STAGE: February 07, 2008
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    We report 121,123Sb nuclear quadrupole resonance (NQR) measurements in the filled-skutterudite superconductor PrOs4Sb12 in the temperature range of 0.05–30 K. The electric field gradients (EFG), Vzz and VxxVyy, at the Sb site exhibit unusual temperature dependence below 30 K. To explain these features, we discuss the coupling between the Sb nuclear quadrupole moment and Pr 4f2-derived multipole moments. The observed T dependence of EFG is well explained by the CEF pseudo-quartet consisting of Γ1 singlet and Γ4(2) triplet states in the cubic point group Th. These results, in turn, are indicative of the importance of the coupling between the 121,123Sb quadrupole moments and the hexadecapole moment caused by the pseudo-quartet.
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  • J. H. Li, B. X. Liu
    2005 Volume 74 Issue 10 Pages 2699-2702
    Published: October 15, 2005
    Released on J-STAGE: February 07, 2008
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    Applying proven realistic Ni–Hf and Ni–Ti potentials, molecular dynamics simulations are performed on the Ni–Hf and Ni–Ti solid solution models, respectively. Simulations reveal that the supersaturated Hf-based and Ti-based lattices upon dissolving about 18 and 7 at. % of Ni, respectively, would turn into a face-centered orthorhombic (fco) phase through an hcp-to-fco martensitic phase transformation. The invariant crystalline plane in the transformation is identified to be (01\\bar10)hcp and the orientation relationships are deduced to be (0001)hcp||(001)fco and [1000]hcp||[1\\bar10]fco, respectively. It is proposed that the observed phase transformation is accomplished through four simultaneous actions, i.e., sliding, shearing, stretching and lattice constant readjusting. In addition, the correlations between the initial hcp and final fco structures as well as the lattice point correspondence are also deduced.
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  • Hidetsugu Sakaguchi
    2005 Volume 74 Issue 10 Pages 2703-2707
    Published: October 15, 2005
    Released on J-STAGE: February 07, 2008
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    We study numerically a dynamic scaling of a diffusion process involving the Langmuir type adsorption. We find dynamic scaling functions in one and two dimensions and compare them with direct numerical simulations. We study further the dynamic scaling law on fractal surfaces. The adsorption–diffusion process obeys the slow fracton dynamics on the fractal surfaces.
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  • Masahiro Agu, Hideo Akabane
    2005 Volume 74 Issue 10 Pages 2708-2711
    Published: October 15, 2005
    Released on J-STAGE: February 07, 2008
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    The nonequilibrium phonon number dynamics of three-phonon processes are studied for 1⁄f current fluctuation in solid-state materials. It is shown that the excitation of a nonequilibrium acoustic phonon diffuses to thermalize in a wave-number space with a t−1⁄2 long-time tail when the excited phonon interacts with a thermal phonon of nearly zero wave number.
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  • Naoki Kobayashi, Kazuaki Saito, Tatsuya Ozawa, Yoshihiro Yamazaki, Kat ...
    2005 Volume 74 Issue 10 Pages 2712-2715
    Published: October 15, 2005
    Released on J-STAGE: February 07, 2008
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    We have extended dynamic scaling hypothesis to describe the wide range of experiments on growing rough interfaces. An alternative approach of original Family–Vicsek scaling hypothesis was not successfully applied to the growing interfaces of paper wetting in that we obtained unphysical values of roughness exponents. Since very nice data collapse suggested the existence of some kind of dynamic scaling, we have tried to extend the dynamic scaling hypothesis. It was found that the extended dynamic scaling hypothesis can be nicely applied to the growing rough interfaces in paper wetting, yielding values of roughness and growth exponents α\\simeq0.73, β\\simeq0.60, respectively.
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  • Noriko Nakajima, Hitoshi Miyata, Allister Levi Sanchez, Hiroaki Ono, S ...
    2005 Volume 74 Issue 10 Pages 2716-2727
    Published: October 15, 2005
    Released on J-STAGE: February 07, 2008
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    We studied electromagnetic and hadronic longitudinal cascade shower fluctuations created by electron and pion beams with energies of 1, 2, 3, and 4 GeV at KEK. A prototype sampling calorimeter of lead and scintillator sandwich was constructed for future application in a linear collider and used for observing cascade showers. We investigated and formulated the behavior of fluctuations of electromagnetic and hadron showers using a correlation matrix with which we were able to separate the π0 component in the hadron shower fluctuation. As an application, the relation between shower fluctuations and the energy resolution of the calorimeter has been studied.
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  • Mitsuhiro Shibayama, Michihiro Nagao, Satoshi Okabe, Takeshi Karino
    2005 Volume 74 Issue 10 Pages 2728-2736
    Published: October 15, 2005
    Released on J-STAGE: February 07, 2008
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    An evaluation method of incoherent small-angle neutron scattering from softmatter in a parallel-plate shape is proposed. Both transmission and incoherent scattering intensity are uniquely determined as a function of the cross-sections and the sample thickness by taking account of multiple scattering from hydrogen. The validity of the method is examined for mixtures of H2O and D2O, polyethylene having various sample thicknesses, and polymer solutions in D2O.
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  • Hisashi Okamoto, Koji Ohkitani
    2005 Volume 74 Issue 10 Pages 2737-2742
    Published: October 15, 2005
    Released on J-STAGE: February 07, 2008
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    We consider the equations of motion of incompressible fluid. Several examples of blow-up for model equations are studied in order to suggest that the existence of the convection term plays a crucial role in the global existence of smooth solutions of some equations including the two-dimensional Euler equations. If we may say so, the convection term suppresses the blow-up of solutions.
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  • Hideshi Fujishita, Yuya Ishikawa, Akira Ogawaguchi, Kenichi Kato, Eiji ...
    2005 Volume 74 Issue 10 Pages 2743-2747
    Published: October 15, 2005
    Released on J-STAGE: February 07, 2008
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    We present structures of PbHfO3 between 100 and 525 K analyzed by a Rietveld method using synchrotron radiation. Spontaneous strain of a perovskite sublattice could be excellently expressed by a conventional phenomenological theory in a room-temperature antiferroelectric phase. Pb shifts along the a-axis and the square root of the spontaneous strain showed similar dependence on temperature as expected from the theory below 200 K, while one of the shifts showed a slight deviation at high temperature. Disordered arrangement of Pb atoms in the cubic phase was found as in the cubic phase of PbZrO3, though the direction of the disorder in PbHfO3 was not so obvious as that in PbZrO3.
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  • Shinsuke Sawae, Terumi Nakashima, Hirotake Shigematsu, Hironobu Kasano ...
    2005 Volume 74 Issue 10 Pages 2748-2753
    Published: October 15, 2005
    Released on J-STAGE: February 07, 2008
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    In order to explain why Rb2SeO4 remains in normal phase down to 0 K while K2SeO4 transforms into the modulated phase at finite temperature, crystal structures of the mixed system have been refined at room temperature by X-ray single crystal analysis. Rb ion can be substituted for K ion with keeping the macroscopic symmetry of space group Pnam. Larger size of Rb ion occupies preferentially site 1, while smaller K ion prefers site 2. Here the atomic distance between an alkali ion and oxygen atoms is longer at site 1 than at site 2. The mean substitution ratio coincides with that from chemical analysis, however, the crystallographic structure analysis is only one method to determine the ratios at each site separately. A sublattice model is discussed to interpret the ion replacing effect on the phonon dispersion relation of the mixed crystal system. The hardening of the soft mode branch can be predicted by the change of interactions between the SeO4 tetrahedrons if the alkali ions are replaced.
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  • Akiko Nakao, Reizo Kato
    2005 Volume 74 Issue 10 Pages 2754-2763
    Published: October 15, 2005
    Released on J-STAGE: February 07, 2008
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    We have studied crystal structures of two Pd(dmit)2-based molecular conductors, Et2Me2Sb[Pd(dmit)2]2 and Cs[Pd(dmit)2]2, above and below their phase transition temperatures. The Et2Me2Sb salt undergoes a first-order transition from a Mott insulator to a non-magnetic state at ca. 70 K, while the Cs salt exhibits a metal-to-insulator (M–I) transition at ca. 56 K with decreasing temperature. These salts are composed of crystallographically equivalent dimeric units [Pd(dmit)2]2 above the transition temperatures. The low temperature structures have been revealed to have two crystallographically independent dimers arranged alternately along the b axis. The structural changes of the dimers have been analyzed by calculations of overlap integrals, to show that the degree of the dimerization changes through the phase transitions. This indicates that both of the phase transitions are characterized by the charge separation, 2dimer→dimer0+dimer2−. Crystal structure of a related compound, Et3MeSb[Pd(dmit)2]3 is also described.
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  • Tomoya Isoshima
    2005 Volume 74 Issue 10 Pages 2764-2768
    Published: October 15, 2005
    Released on J-STAGE: February 07, 2008
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    We study the Bose–Einstein condensate of atomic Boson gases trapped in a composite potential comprising a harmonic potential and an optical lattice potential. We observed a series of collective excitations that induces localized vortex oscillations with a characteristic wavelength. The oscillations can be observed experimentally when the radial confinement is tight. We present the excitation spectra of the vortex oscillation modes and propose a method to experimentally excite the modes.
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  • Kota Hanasaki, Masatoshi Imada
    2005 Volume 74 Issue 10 Pages 2769-2782
    Published: October 15, 2005
    Released on J-STAGE: February 07, 2008
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    The Hubbard model with additional intersite interaction ‘V’ (the extended Hubbard model) is investigated by the correlator projection method (CPM). CPM is a newly developed numerical method that combines the equation-of-motion approach and the dynamical mean-field theory. Using this method, properties of the extended Hubbard Model at quarter filling are discussed with special emphasis on the metal–insulator transition induced by electron–electron correlations. As we increase the interaction, a metal–insulator transition to a charge ordered insulator with antiferromagnetic order occurs at low temperatures, but a metal–insulator transition to a charge ordered insulator without magnetic symmetry breaking occurs at intermediate temperatures. Here, the magnetic order is found to be confined to low temperatures because of the smallness of the exchange coupling Jeff. The present results are in sharp contrast to the Hatree–Fock approximation whereas they are in agreement with the experimental results on quarter-filled materials with strong correlations such as organic BEDT-TTF conductors.
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  • S. Kaji, G. Oomi, M. Hedo, Y. Uwatoko, S. Mitani, K. Takanashi, S. Tak ...
    2005 Volume 74 Issue 10 Pages 2783-2790
    Published: October 15, 2005
    Released on J-STAGE: February 07, 2008
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    The tunnel magnetoresistance (TMR) and the temperature dependence of electrical resistivity ρ(T) in insulating Co–Al–O granular films have been studied under high pressure. It is found that the temperature dependence of ρ is affected significantly by applying pressure and the behavior of ρ(T) becomes close to the metallic behavior at high pressure. Furthermore, TMR at low temperatures is enhanced up to 5 GPa, while it decreases with increasing pressure above that. The results provide an evidence that the successive onset of higher-order processes in tunneling conduction at low temperatures below about 50 K is enhanced at high pressure lower than 5 GPa. On the other hand, TMR at 77 K and room temperature (RT) decreases monotonously as pressure increases. The large difference in the pressure dependence of TMR between 4.2 K and the higher temperature is consistently explained by taking into account the higher order tunneling theory and the pressure induced percolation. The metal-insulator transition and the pressure dependence of TMR at 4.2 K are also discussed on the basis of the percolation theory.
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  • Hironori Kawashima, Hiroyasu Tanaka, Shinji Kawaji
    2005 Volume 74 Issue 10 Pages 2791-2796
    Published: October 15, 2005
    Released on J-STAGE: February 07, 2008
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    Collapse of the quantized Hall resistance (QHR) RH(4) in high precision and change in the diagonal resistivity ρxx with the increase in source–drain current ISD are measured in GaAs/AlGaAs heterostructure Hall bars used for the confirmation of the sample-width independent accuracy of the RH(i) (i: an integer) by Jeanneret et al. [IEEE Trans. Instrum. Meas. 44 (1995) 254]. Compared with our butterfly-type Hall bars, the Jeanneret-type Hall bars show the same behavior in the collapse of the QHR while the change in ρxx against ISD shows significantly different behavior. Jeanneret-type Hall bars appear to show more homogeneous electronic properties than butterfly-type Hall bars. Effect of structures of the central narrow channel and voltage probes for ρxx and RH measurement in both Hall bars and correlation between the deviation of the Hall resistance ΔRH=RHRH(4) and ρxx with the increase in ISD are discussed.
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  • Akira Endo, Yasuhiro Iye
    2005 Volume 74 Issue 10 Pages 2797-2805
    Published: October 15, 2005
    Released on J-STAGE: February 07, 2008
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    Detailed analysis of the commensurability oscillation (CO) has been performed on unidirectional lateral superlattices with periods ranging from a=92 to 184 nm. Fourier analysis reveals the second (and the third) harmonics along with the fundamental oscillation for a≥138 nm (184 nm) at low-enough temperature, evincing the presence of corresponding harmonics in the profile of the potential modulation. The harmonics manifest themselves in CO with demagnified amplitude due to the low-pass filtering action of the thermal damping factor; with a suitable consideration of the damping effect, the harmonics of the modulation potential are found to have the amplitudes V2 and V3 up to roughly 30% of that of the fundamental component V1, despite the small ratio of the period a to the depth d\\simeq99 nm of the two-dimensional electron gas (2DEG) from the surface. The dependence of Vn on a indicates that the fundamental component originates at the surface, while the higher harmonics arise from the effect of the strain that penetrates down into subsurface. The manipulation of high harmonics thus provides a useful technique to introduce small length-scale modulation into high-mobility 2DEGs located deep inside the wafer.
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  • Ryosuke Kadono, Kazuki Ohishi, Akihiro Koda, Shanta R. Saha, Wataru Hi ...
    2005 Volume 74 Issue 10 Pages 2806-2812
    Published: October 15, 2005
    Released on J-STAGE: February 07, 2008
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    A strong correlation between field-induced antiferromagnetic (AF) order and superconductivity is demonstrated for an electron-doped cuprate superconductor, Pr1−xLaCexCuO4−δ (PLCCO). In addition to the specimen with x=0.11 (which is close to the AF phase boundary, x\\simeq0.10), we show that the specimen with x=0.15 (Tc\\simeq16 K at zero field) also exhibits the field-induced AF order with a reduced magnitude of the induced moment. The uniform muon Knight shift at a low magnetic field (∼102 Oe) indicates that the AF order is not localized within the cores of flux lines, which is in marked contrast to theoretical predictions for hole-doped cuprates. The presence of anomalous nondiagonal hyperfine coupling between muons and Pr ions is also demonstrated in detail.
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  • Takafumi Kita, Masao Arai
    2005 Volume 74 Issue 10 Pages 2813-2830
    Published: October 15, 2005
    Released on J-STAGE: February 07, 2008
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    We study interacting electrons in a periodic potential and a uniform magnetic field B taking the spin-orbit interaction into account. We first establish a perturbation expansion for those electrons with respect to the Bloch states in zero field. It is shown that the expansion can be performed with the zero-field Feynman diagrams of satisfying the momentum and energy conservation laws. We thereby clarify the structures of the self-energy and the thermodynamic potential in a finite magnetic field. We also provide a prescription of calculating the electronic structure in a finite magnetic field within the density functional theory starting from the zero-field energy-band structure. On the basis of these formulations, we derive explicit expressions for the magnetic susceptibility of B0 at various approximation levels on the interaction, particularly within the density functional theory, which include the result of Roth [J. Phys. Chem. Solids 23 (1962) 433] as the non-interacting limit. We finally study the de Haas–van Alphen oscillation in metals to show that quasiparticles at the Fermi level with the many-body effective mass are directly relevant to the phenomenon. The present argument may be more transparent than that by Luttinger [Phys. Rev. 121 (1961) 1251] of using the gauge invariance and has an advantage that the change of the band structure with the field may be incorporated.
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  • Yuji Inagaki, Yasuo Narumi, Koichi Kindo, Hikomitsu Kikuchi, Tomohisa ...
    2005 Volume 74 Issue 10 Pages 2831-2835
    Published: October 15, 2005
    Released on J-STAGE: February 07, 2008
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    High field magnetization processes were measured for the single crystal of an S=1⁄2 ferro-antiferromagnetic delta-chain system [Cu(bpy)(H2O)][Cu(bpy)(mal)–(H2O)](ClO4)2. At low temperatures, the observed magnetization curve shows a rapid increase to half of the saturation moment below about 1 T and then followed by a gradual increase to fully polarized state below about 7 T. Concerning this characteristic magnetization process, we discuss the ground state of the system qualitatively based on a non-interacting two sublattice model, where a delta-chain is divided into apical free spins and remaining basal spins regarded as quasi one dimensional antiferromagnetic chain. Essential effect of ferromagnetic interaction, which connects an apical spin and basal spins, is pointed out from the comparison with theoretical curve for the non-interacting two sublattice model as well as with the numerically calculated curve. Presence of the Dzyaloshinskii–Moriya interaction is also suggested from the arguments for the saturation behavior and/or saturation field itself based on the spin wave theory.
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  • Taiki Ueda, Daisuke Honda, Tomoyuki Shiromoto, Naoto Metoki, Fuminori ...
    2005 Volume 74 Issue 10 Pages 2836-2842
    Published: October 15, 2005
    Released on J-STAGE: February 07, 2008
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    We measured the electrical resistivity, specific heat, magnetic susceptibility, high-field magnetization, neutron scattering and electrical resistivity under pressure for CeRhGe. The anisotropy of the magnetic susceptibility and magnetization are very large, reflecting the orthorhombic crystal structure. The magnetic easy-axis is found to be oriented along the a-axis. From the neutron scattering experiment, the magnetic structure is, however, not simple, indicating an incommensurate antiferromagnetic structure. The magnetic susceptibility and magnetization were analyzed on the basis of the crystalline electric field scheme of localized-4f energy levels, indicating a very large splitting energy of the 4f levels.
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  • Arumugam Thamizhavel, Hiroshi Nakashima, Yoshiko Obiraki, Miho Nakashi ...
    2005 Volume 74 Issue 10 Pages 2843-2848
    Published: October 15, 2005
    Released on J-STAGE: February 07, 2008
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    Single crystals of a pressure-induced superconductor Ce2Ni3Ge5 have been successfully grown by the flux method. The anisotropic magnetic properties due to the orthorhombic crystal structure have been studied precisely by the electrical resistivity, specific heat, magnetic susceptibility, and high-field magnetization measurements. The results of these measurements confirmed two antiferromagnetic transitions at TN1=5.0 K and TN2=4.3 K. The electronic specific heat coefficient obtained from the low-temperature specific heat data amounts to 90 mJ/K2·mol Ce. The high-field magnetization for H||[100] shows four magnetic transitions at 11.8, 12.9, 17.5 and 23.9 T with a saturation moment of 0.73 μB/Ce at 1.3 K. On the other hand, two magnetic transitions are observed for H||[010] and [001], with saturation moments of 0.43 and 1.1 μB/Ce, respectively. We have also performed the crystalline electric field (CEF) analysis on the magnetic susceptibility and magnetization to understand the magnetocrystalline anisotropy, where the splitting energies of two excited doublets in the CEF scheme are estimated to be 140 and 576 K, respectively.
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  • Jun Matsui, Yasuaki Hiwatari
    2005 Volume 74 Issue 10 Pages 2849-2852
    Published: October 15, 2005
    Released on J-STAGE: February 07, 2008
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    We compute the high-frequency spectra of the intermolecular dipole moment correlation for a model polymer near the glass transition by molecular dynamics simulation without charge distribution. The dielectric properties are calculated by introducing the inherent dipoles which are virtually placed along the chains as forming the type-A polymer. The high-frequency loss peak corresponding to the local motions of molecules is observed at around 10 THz. The spectra are strongly deviated from a Lorentian distribution, which causes a large so-called tangential delta near the peak frequency as well.
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  • Norifumi L. Yamada, Hideki Seto, Takayoshi Takeda, Michihiro Nagao, Yo ...
    2005 Volume 74 Issue 10 Pages 2853-2859
    Published: October 15, 2005
    Released on J-STAGE: February 07, 2008
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    The temperature and CaCl2 concentration dependence of the lamellar repeat distance of a dipalmitoylphosphatidylcholine (DPPC) aqueous solution was investigated by small-angle X-ray and neutron scattering, and neutron spin echo. At certain CaCl2 concentrations, the repeat distance in the liquid-crystalline phase tends to increase up to infinity while that in the gel phase has an upper limit. This behavior is attributable to the fact that the steric repulsion of lipid bilayers due to the membrane undulation in the liquid-crystalline phase is larger than that in the gel phase. The free-energy calculation suggested that the cooperation of the short-range electrostatic interaction and the long-range steric interaction is the origin of the increase in the repeat distance in the liquid-crystalline phase, and it can be the origin of an “unbinding transition”.
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  • K. H. Chang, Kyungsik Kim, M.-K. Yum, J. S. Choi, T. Odagaki
    2005 Volume 74 Issue 10 Pages 2860-2861
    Published: October 15, 2005
    Released on J-STAGE: February 07, 2008
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  • Changping Yang, Masahumi Kohgi, Kazuaki Iwasa, Hitoshi Sugawara, Hidey ...
    2005 Volume 74 Issue 10 Pages 2862-2863
    Published: October 15, 2005
    Released on J-STAGE: February 07, 2008
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  • Keiji Kosaka
    2005 Volume 74 Issue 10 Pages 2864-2865
    Published: October 15, 2005
    Released on J-STAGE: February 07, 2008
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  • Joseph N. Grima, Ruben Gatt, Andrew Alderson, Kenneth E. Evans
    2005 Volume 74 Issue 10 Pages 2866-2867
    Published: October 15, 2005
    Released on J-STAGE: February 07, 2008
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  • Daiichiro Sekiba, Kan Nakatsuji, Fumio Komori
    2005 Volume 74 Issue 10 Pages 2868-2869
    Published: October 15, 2005
    Released on J-STAGE: February 07, 2008
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  • Noriaki K. Sato, Naofumi Aso
    2005 Volume 74 Issue 10 Pages 2870-2871
    Published: October 15, 2005
    Released on J-STAGE: February 07, 2008
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  • Manabu Hasegawa
    2005 Volume 74 Issue 10 Pages 2872-2873
    Published: October 15, 2005
    Released on J-STAGE: February 07, 2008
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