Journal of the Physical Society of Japan
Online ISSN : 1347-4073
Print ISSN : 0031-9015
ISSN-L : 0031-9015
Volume 76, Issue 6
Displaying 1-49 of 49 articles from this issue
  • Kouichi Okunishi
    2007 Volume 76 Issue 6 Pages 063001
    Published: June 15, 2007
    Released on J-STAGE: August 12, 2010
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    We present a novel real-space renormalization group (RG) for the one-dimensional XXZ model in the critical regime, reconsidering the role of the cutoff parameter in Wilson’s RG for the Kondo impurity problem. We then demonstrate the RG calculation for the XXZ chain with the free boundary. Comparing the hierarchical structure of the obtained low-energy spectrum with the Bethe ansatz result, we find that the proper scaling dimension is reproduced as a fixed point of the RG transformation.
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  • Akinori Nishino, Naomichi Hatano
    2007 Volume 76 Issue 6 Pages 063002
    Published: June 15, 2007
    Released on J-STAGE: August 12, 2010
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    An open quantum system consisting of a quantum dot with a Coulomb interaction and two leads without interactions is studied. The many-body scattering states are constructed with the Bethe-ansatz approach. The expectation value of the electric current is exactly calculated for the scattering states to observe resonance peaks due to many-body scattering.
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  • Dai Aoki, Yoshinori Haga, Tatsuma D. Matsuda, Naoyuki Tateiwa, Shugo I ...
    2007 Volume 76 Issue 6 Pages 063701
    Published: June 15, 2007
    Released on J-STAGE: August 12, 2010
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    We succeeded in growing a new transuranium compound NpPd5Al2 with the tetragonal crystal structure by the Pb-flux method, and measured the electrical resistivity, specific heat, magnetic susceptibility and magnetization. NpPd5Al2 is found to be a paramagnetic heavy-fermion superconductor with strong coupling ΔC⁄γTc=2.33 [Tc=4.9 K and γ=200 mJ/(K2·mol)]. The upper critical field Hc2 at 0 K is large and highly anisotropic: Hc2(0)=37 kOe for H||[100] and Hc2(0)=143 kOe for H||[001]. Hc2 is found to be strongly suppressed by the magnetic field, and the magnetization curve indicates a step-like increase at Hc2, which are due to the paramagnetic effect. The low-temperature electronic specific heat approximately follows the T3-dependence, indicating the existence of point nodes in the energy gap. The d-wave superconductivity with point nodes is most likely realized in this compound.
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  • Youhei Yamaji, Takahiro Misawa, Masatoshi Imada
    2007 Volume 76 Issue 6 Pages 063702
    Published: June 15, 2007
    Released on J-STAGE: August 12, 2010
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    We clarify that metamagnetic transitions in three dimensions show unusual properties as quantum phase transitions if they are accompanied by changes in Fermi-surface topology. An unconventional universality deeply affected by the topological nature of Lifshitz-type transitions emerges around the marginal quantum critical point (MQCP). Here, the MQCP is defined by the meeting point of the finite temperature critical line and a quantum critical line running on the zero temperature plane. The MQCP offers a marked contrast with the Ising universality and the gas–liquid-type criticality satisfied for conventional metamagnetic transitions. At the MQCP, the inverse magnetic susceptibility χ−1 has a diverging slope as a function of the magnetization m (namely, |dχ−1dm|→∞) in one side of the transition, which should not occur in any conventional quantum critical phenomena. The exponent of the divergence can be estimated even at finite temperatures. We propose that such an unconventional universality indeed accounts for the metamagnetic transition in ZrZn2.
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  • Akihiro Koda, Ryosuke Kadono, Kazuki Ohishi, Shanta R. Saha, Wataru Hi ...
    2007 Volume 76 Issue 6 Pages 063703
    Published: June 15, 2007
    Released on J-STAGE: August 12, 2010
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    We report on the muon spin rotation/relaxation study of a pyrochlore oxide, Cd2Os2O7, which exhibits a metal–insulator (MI) transition at TMI\\simeq225 K without structural phase transition. It reveals strong spin fluctuation (≥108 s−1) below the MI transition, suggesting a predominant role of geometrical spin frustration amongst Os5+ ions. Meanwhile, upon further cooling, an incommensurate spin density wave discontinuously develops below TSDW\\simeq150 K. These observations strongly suggest the occurrence of an anomalous magnetic transition and associated change in the local spin dynamics in undistorted pyrochlore antiferromagnet.
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  • Ken Matsuba, Shunsuke Yoshizawa, Yugo Mochizuki, Takashi Mochiku, Kazu ...
    2007 Volume 76 Issue 6 Pages 063704
    Published: June 15, 2007
    Released on J-STAGE: August 12, 2010
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    In the vortex core of slightly overdoped Bi2Sr2CaCu2Ox, the electron- and hole-like states have been found to exhibit spatial modulations in anti-phase with each other along the Cu–O bonding direction. Some kind of one-dimensionality has been observed in the vortex core, and it is more clearly seen in differential conductance maps at lower biases below ±9 mV.
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  • Daisuke Yoshizumi, Yuji Muraoka, Yoshihiko Okamoto, Yoko Kiuchi, Jun-I ...
    2007 Volume 76 Issue 6 Pages 063705
    Published: June 15, 2007
    Released on J-STAGE: August 12, 2010
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    Electronic properties of the sodium cobaltate NaxCoO2 are systematically studied through a precise control of band filling. Resistivity, magnetic susceptibility and specific heat measurements are carried out on a series of high-quality polycrystalline samples prepared at 200 °C with Na content in a wide range of 0.35≤x≤0.70. It is found that dramatic changes in electronic properties take place at a critical Na concentration x* that lies between 0.58 and 0.59, which separates a Pauli paramagnetic and a Curie–Weiss metals. It is suggested that at x* the Fermi level touches the bottom of the a1g band at the Γ point, leading to a crucial change in the density of states across x* and the emergence of a small electron pocket around the Γ point for x>x*.
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  • Rieko Morisaki, Toshio Ono, Hidekazu Tanaka, Hiroyuki Nojiri
    2007 Volume 76 Issue 6 Pages 063706
    Published: June 15, 2007
    Released on J-STAGE: August 12, 2010
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    Thermodynamic properties and elementary excitations in S=1⁄2 one-dimensional Heisenberg antiferromagnet KCuGaF6 were investigated by magnetic susceptibility, specific heat and ESR measurements. Due to the Dzyaloshinsky–Moriya interaction with alternating D-vectors and/or the staggered g-tensor, the staggered magnetic field is induced when subjected to external magnetic field. Specific heat in magnetic field clearly shows the formation of excitation gap, which is attributed to the staggered magnetic field. The specific heat data was analyzed on the basis of the quantum sine-Gordon (SG) model. We observed many ESR modes including one soliton and three breather excitations characteristic of the quantum SG model.
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  • Nao Takeshita, Chieko Terakura, Yoshinori Tokura, Ayako Yamamoto, Hide ...
    2007 Volume 76 Issue 6 Pages 063707
    Published: June 15, 2007
    Released on J-STAGE: August 12, 2010
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    Recently discovered pyrochlore oxide, Hg2Ru2O7, shows a first order metal–insulator transition at T∼107 K. The effect of hydrostatic pressure on the M–I transition was studied by measuring the temperature dependent resistivity ρ(T) up to 12 GPa. The application of pressure suppressed the low temperature insulating state and eventually induced a transition from a correlated insulator to a metal at around 5 GPa. With decreasing temperature, ρ(T) in the metallic phase showed a rapid decrease at around T*∼40 K, likely representing the onset of a coherent–incoherent crossover, and eventually a well defined T2-dependence at low temperatures, indicative of the presence of coherent quasi-particles. All these results point the formation of a Fermi liquid with an enhanced mass in the metallic state of this geometrically frustrated system, located close proximity to the correlation driven metal–insulator transition.
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  • Kaoru Iwano, Yukihiro Shimoi
    2007 Volume 76 Issue 6 Pages 063708
    Published: June 15, 2007
    Released on J-STAGE: August 12, 2010
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    Novel halogen-bridged platinum complexes, namely, their two-leg ladder versions, have been synthesized for the first time and their basic properties including optical spectra are now available. Motivated by this progress, we investigate chlorine-bridged systems by density-functional-theory calculations. Our scope is over various geometrical types such as a monomer, a single chain, and ladders. We treat not only ground states but also excited states, calculating optical conductivity spectra, which show features specific to the ladder systems. As a result of a comparison with the experimental spectra, an overall agreement is at least qualitatively attained and a new mechanism of hole photo-doping is proposed.
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  • Aya Yamamoto, Shinji Wada, John L. Sarrao
    2007 Volume 76 Issue 6 Pages 063709
    Published: June 15, 2007
    Released on J-STAGE: August 12, 2010
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    We have investigated evolution of transport and low-energy spin fluctuation properties of the heavy fermion compound YbAuCu4 with the application of magnetic field, and found that the material can be driven from the originally antiferromagnetically (AFM) ordered ground state (Néel temperature TN∼0.8 K) to a nonmagnetic Fermi liquid one through the field-tuned quantum critical point (QCP) at Hcr\\simeq13 kOe. The electrical resistivity measurement down to 55 mK in the vicinity of Hcr (TN→0) provides evidence for the increase in the inelastic scattering of heavy electrons, and the 63Cu spin-lattice relaxation rate 1⁄T1T measurement down to 1.35 K near Hcr exhibits the occurrence of the AFM order instability. Temperature and field participating in the non-Fermi liquid (NFL) phenomena in the vicinity of Hcr are about one order higher in energy than those in YbRh2Si2 that has been intensively investigated as only one NFL material among the stoichiometric Yb-based compounds. It is mentioned that in both compound, the quasiparticle mass does not diverge but remains finite in the field-tuned QCP. An additional new information provided in this study is that the Kondo temperature TK derived from the resisitivity maximum and/or the 1⁄T1T maximum monotonically increases with increasing field, contrary to the increase in the localization character of f electrons.
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  • Hiroshi Kohno, Junya Shibata
    2007 Volume 76 Issue 6 Pages 063710
    Published: June 15, 2007
    Released on J-STAGE: August 12, 2010
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    Previous calculation of spin torques for small-amplitude magnetization dynamics around a uniformly magnetized state [J. Phys. Soc. Jpn. 75 (2006) 113706] is extended here to the case of finite-amplitude dynamics. This is achieved by introducing an “adiabatic” spin frame for conduction electrons, and the associated SU(2) gauge field. In particular, the Gilbert damping is shown to arise from the time variation of the spin-relaxation source terms in this new frame, giving a new physical picture of the damping. The present method will allow a “first-principle” derivation of spin torques without any assumptions such as rotational symmetry in spin space.
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  • Yoshihiro Tsujimoto, Yoichi Baba, Noriaki Oba, Hiroshi Kageyama, Tomoy ...
    2007 Volume 76 Issue 6 Pages 063711
    Published: June 15, 2007
    Released on J-STAGE: August 12, 2010
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    A new triple-layered perovskite (CuBr)Sr2Nb3O10 with the S=1⁄2 square lattice has been prepared through a chimie douce route. Presence of strong spin frustration is inferred from zero-field specific heat measurements which exhibit successive phase transitions at 9.3 and 7.5 K. Application of magnetic fields merges the transition temperatures at 3 T, suggesting that the intermediate phase is of magnetic origin with fluctuating spin–spin correlation. Despite the square geometry, magnetization curves have revealed a metamagnetic transition to a novel phase characterized by a 1/3 plateau of the saturated magnetization.
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  • Mitsusada M. Sano, Yuichi Yatsuyanagi, Takeshi Yoshida, Hiroyuki Tomit ...
    2007 Volume 76 Issue 6 Pages 064001
    Published: June 15, 2007
    Released on J-STAGE: August 12, 2010
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    A statistical mechanical theory of the energy spectrum for two-dimensional N-point vortex systems is developed. The system in an infinite plane is considered. We focus our attention on the energy spectrum of the system “in equilibrium” and “in a transient state”. For like-sign point vortex systems in an infinite plane, we have succeeded in deriving a scaling law of the energy spectrum E(k)∼k−α for the intermediate k regime, via the 2-point correlation function R2(r). However, the applicability of the derived scaling law is limited by the validity of the asymptotic expansion used. By a direct numerical simulation, we obtain various powers α=2.11–3.19 for transient states. Using the Monte Carlo simulation, for equilibrium states we find that the energy spectrum in the intermediate regime does not obey a power law. It is concluded that for point vortex systems in an infinite plane, the scaling law of the energy spectrum in equilibrium and in the transient state depends on the system parameters, and is thus not universal.
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  • Satoshi Morita, Hidetoshi Nishimori
    2007 Volume 76 Issue 6 Pages 064002
    Published: June 15, 2007
    Released on J-STAGE: August 12, 2010
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    Convergence conditions for quantum annealing are derived for optimization problems represented by the Ising model of a general form. Quantum fluctuations are introduced as a transverse field and/or transverse ferromagnetic interactions, and the time evolution follows the real-time Schrödinger equation. It is shown that the system stays arbitrarily close to the instantaneous ground state, finally reaching the target optimal state, if the strength of quantum fluctuations decreases sufficiently slowly, in particular inversely proportionally to the power of time in the asymptotic region. This is the same condition as the other implementations of quantum annealing, quantum Monte Carlo and Green’s function Monte Carlo simulations, in spite of the essential difference in the type of dynamics. The method of analysis is an application of the adiabatic theorem in conjunction with an estimate of a lower bound of the energy gap based on the recently proposed idea of Somma et al. for the analysis of classical simulated annealing using a classical-quantum correspondence.
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  • Shohei Watabe, Tetsuro Nikuni, Nicolai Nygaard, James E. Williams, Cha ...
    2007 Volume 76 Issue 6 Pages 064003
    Published: June 15, 2007
    Released on J-STAGE: August 12, 2010
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    We determine the adiabatic phase diagram of a resonantly-coupled system of Fermi atoms and Bose molecules confined in a harmonic trap by using the local density approximation. The adiabatic phase diagram shows the fermionic condensate fraction composed of condensed molecules and Cooper paired atoms. The key idea of our work is conservation of entropy through the adiabatic process, extending the study of Williams et al. [New J. Phys. 6 (2004) 123] for an ideal gas mixture to include the resonant interaction in a mean-field theory. We also calculate the molecular conversion efficiency as a function of initial temperature. Our work helps to understand recent experiments on the BCS–BEC crossover, in terms of the initial temperature measured before a sweep of the magnetic field.
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  • Kaito Umemura, Kuniyoshi Ebina
    2007 Volume 76 Issue 6 Pages 064004
    Published: June 15, 2007
    Released on J-STAGE: August 12, 2010
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    We introduce an energy dissipation model for traffic flow based on the optimal velocity model (OV model). In this model, vehicles are defined as moving under the rule of the OV model, and energy dissipation rate is defined as the product of the velocity of a vehicle and resistant force which works to it. According to the results of numerical simulation on the periodic boundary condition, the energy dissipation depends on traffic conditions, such as congestion (traffic jam), and therefore depends on parameters and initial conditions of the system. The results of simulation indicate that, although the flux of vehicular transportation is not so different between at a state of free flow and that of congestion, the energy dissipation reveals a burst at a state of congestion. Additionally, how the burst behaves depends on how congestion appears.
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  • Takeya Tsurumi
    2007 Volume 76 Issue 6 Pages 064005
    Published: June 15, 2007
    Released on J-STAGE: August 12, 2010
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    Surface polariton propagation between a gyrotropic medium with arbitrary magnetization direction and an isotropic medium is investigated. Assuming that both the permittivity and the permeability of the gyrotropic medium are anisotropic, the dispersion relation equation for the surface polaritons is derived, which is applied to specific configurations of the propagation direction of the surface polaritons, the magnetization and the interface. When the gyrotropic effect is sufficiently weak, which means that the permittivity and the permeability of the gyrotropic medium are nearly isotropic, the influence of the magnetization direction on the propagation characteristics of the surface polaritons, such as the emergence of nonreciprocity, is investigated in detail.
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  • Takafumi Kita
    2007 Volume 76 Issue 6 Pages 064006
    Published: June 15, 2007
    Released on J-STAGE: August 12, 2010
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    The previous investigation on Rayleigh–Bénard convection of a dilute classical gas [T. Kita: J. Phys. Soc. Jpn. 75 (2006) 124005] is extended to calculate entropy change of the convective transition with the rigid boundaries. We obtain results qualitatively similar to those of the stress-free boundaries. Above the critical Rayleigh number, the roll convection is realized among possible steady states with periodic structures, carrying the highest entropy as a function of macroscopic mechanical variables.
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  • S. Strokov, V. Biryukov, Yu. Chesnokov, I. Endo, M. Iinuma, H. Kuroiwa ...
    2007 Volume 76 Issue 6 Pages 064007
    Published: June 15, 2007
    Released on J-STAGE: August 12, 2010
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    Two experiments on the deflection of electron and proton beams using silicon crystals were performed to study the channeling effect. An experiment on deflection of a 150-MeV electron beam by a crystal with the thickness of 16 μm was conducted at the REFER ring (Relativistic Electron Facility for Education and Research, Hiroshima University). The maximum deflection angle of 0.2 mrad was achieved. A 12-GeV proton beam was deflected by an 1-cm long crystal, which was bent at an angle of 32.6 mrad, at the KEK Proton Synchrotron. Results of these experiments are presented in this article. As for application, a possibility to create a deflection system for the J-PARC (Japan Proton Accelerator Complex) and a collimator for the ILC (International Linear Collider) are discussed as well.
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  • Kaoru Taketani, Yoshichika Seki, Haruhiko Funahashi, Masahiro Hino, Ma ...
    2007 Volume 76 Issue 6 Pages 064008
    Published: June 15, 2007
    Released on J-STAGE: August 12, 2010
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    We have revealed the criterion to observe moiré fringes in a neutron spin interferometry. In former studies using wave front division, neutron beam had to be collimated by fine slits. On the other hand, we have succeeded to observe moiré fringes with divergence angle of 8.3 mrad using spin polarization division. A model based on partial coherence theory has been developed and verified experimentally. These results will be the basis for neutron wave front manipulation technique using magnetic birefringence.
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  • Ryo Maezono, Hirofumi Watanabe, Shigenori Tanaka, M. D. Towler, R. J. ...
    2007 Volume 76 Issue 6 Pages 064301
    Published: June 15, 2007
    Released on J-STAGE: August 12, 2010
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    The total energy of a small polypeptide system is calculated by combining the quantum Monte Carlo (QMC) and fragment molecular orbital (FMO) methods. Electronic correlation is taken into account using Slater–Jastrow wave functions and the variational quantum Monte Carlo (VMC) method. We calculate the energy of the whole system directly and by using the FMO method, finding that the combined QMC–FMO approach works very well.
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  • Youhei Fujitani
    2007 Volume 76 Issue 6 Pages 064401
    Published: June 15, 2007
    Released on J-STAGE: August 12, 2010
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    Unlike in conventional hydrodynamics, the viscosity is assumed to smoothly change across a thin interfacial region between two fluid-phases in the fluid particle dynamics (FPD) method, which was proposed to facilitate the numerical study of colloidal dynamics. We study how the pressure and velocity fields are connected in the limit of the thin interfacial region by use of the steady Stokes approximation. We obtain connection formulas to calculate the fields in and around a droplet, far from which the uniform flow or the linear shear flow is imposed. We also show, around a spherical rigid particle in a steady state where the particle center moves uniformly, that the FPD method yields the flow consistent with that of conventional hydrodynamics.
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  • Seiya Nishimura, Masatoshi Yagi, Sanae-I. Itoh, Masahumi Azumi, Kimita ...
    2007 Volume 76 Issue 6 Pages 064501
    Published: June 15, 2007
    Released on J-STAGE: August 12, 2010
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    The parameter dependence of the linear growth rate of collisional drift-tearing mode is investigated numerically and analytically using reduced two-fluid equations. Especially, the effect of parallel thermal transport on the growth rate is clarified. It is newly found that the thermal transport parallel to the ambient magnetic field line destabilizes the collisional drift-tearing mode and the diamagnetic drift frequency acts as an instability source in some parameter regime. With large parallel thermal transport coefficient, the collisional drift-tearing mode could be unstable even if the classical tearing mode is stable.
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  • Kazuyuki Matsubayashi, Keiichiro Imura, Hiroyuki S. Suzuki, Takafumi M ...
    2007 Volume 76 Issue 6 Pages 064601
    Published: June 15, 2007
    Released on J-STAGE: August 12, 2010
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    We have grown single crystals of SmS and investigated effects of nominal composition on the electrical resistivity, optical reflectivity, magnetoresistance, dc magnetization, and specific heat. We report that nominally stoichiometric and S-excess samples have an energy gap (Eg) of about 950 (±100) K while Sm-excess samples possess Eg of about 1500 (±100) K, and further that these values of Eg correlate with the lattice constant. These findings were interpreted as the chemical pressure effect. As an external magnetic field is increased, Eg monotonically decreases albeit in the nonmagnetic black phase, which can be an origin of reported negative magnetoresistance. The low-temperature specific heat under pressure shows the presence of an intrinsic γ-term in the golden phase in addition to a spurious
    γ-coefficient arising from secondary phases such as Sm3S4.
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  • Kenta Ikawa, Masahide Sato, Makio Uwaha
    2007 Volume 76 Issue 6 Pages 064602
    Published: June 15, 2007
    Released on J-STAGE: August 12, 2010
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    A Si(111) vicinal face near 860 °C consists of the 1×1 structure and the 7×7 structure. The 1×1 structure is on the lower side and the 7×7 structure is on the upper side of steps. The diffusion coefficient on the 1×1 structure is larger than that on the 7×7 structure. We study drift-induced step instabilities with two different diffusion coefficients. Irrespective of the drift direction, step bunching occurs with the drift. The ratio of the width of the two regions changes with the drift: the structure with fast diffusion is dominant with step-down drift and that with slow diffusion is dominant with step-up drift. Bunches with step-up drift are more straight than that with step-down drift. If the repulsive interaction between a step and a structural boundary is strong enough to suppress the step bunching, the inphase step wandering occurs and grooves perpendicular to the steps appear with step-up drift.
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  • Tadao Ishii
    2007 Volume 76 Issue 6 Pages 064603
    Published: June 15, 2007
    Released on J-STAGE: August 12, 2010
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    In one- through three-dimensional (1D–3D) simple lattices equipped with a uniform distribution of symmetric activation energies, effective medium approximation (EMA) is examined to see how it accurately reproduces the exact dynamic behavior of ion-hopping conduction obtained by the relaxation mode theory (RMT). Without introducing any other approximations, dc conductivity is derived and compared with RMT results. It is found that the activation energies are quite consistent with RMT and percolation results in the 1D and 2D systems, but deviate from those in the 3D system. On the other hand, the ac conductivity formulas are carefully obtained at low frequencies, and the accompanying scaling properties are investigated and compared in terms of RMT behavior; again, 2D- and 3D-EMAs do not well reproduce RMT results. The ac part of EMA conductivity is also clarified in the lowest-frequency regime, giving rise to another power law as has already been discussed in RMT.
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  • Hidekazu Sato, Toshiro Sakakibara, Takashi Tayama, Takahiro Onimaru, H ...
    2007 Volume 76 Issue 6 Pages 064701
    Published: June 15, 2007
    Released on J-STAGE: August 12, 2010
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    Field-orientation dependences of the magnetization M(H,θ) and the ordering temperature TA(H,θ) of the low-field phase (A-phase) of the filled skutterudite compound PrFe4P12 have been studied in detail at low temperatures down to 0.3 K, by means of angle-resolved magnetization measurements. Both M(H,θ) deep inside the A-phase and TA(H,θ) show a smooth angular variation with a cubic anisotropy when H is rotated within the (001) and (1\\bar10) planes. The results strongly suggest that the order parameter of the A-phase is of scalar (Γ1+) type which, together with the (1,0,0) ordering vector, preserves the cubic symmetry. The magnitude of the cubic anisotropy term in the magnetization in the ordered state at low temperatures is found to vary with H and exhibits a sign reversal at ∼2.3 T.
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  • Nguyen Van Hieu, Tetsuya Takeuchi, Hiroaki Shishido, Chie Tonohiro, Ts ...
    2007 Volume 76 Issue 6 Pages 064702
    Published: June 15, 2007
    Released on J-STAGE: August 12, 2010
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    A series of ternary compounds RRhIn5 (R: rare earth) has been grown in the single crystalline form by means of the flux method. The magnetic properties of these compounds were investigated by measuring the lattice parameter, electrical resistivity, specific heat, magnetic susceptibility and magnetization. All the compounds crystallize in the tetragonal HoCoGa5-type structure. Most of these compounds order antiferromagnetically at low temperatures, except when R=Y, La, Pr, and Yb. The observed temperature dependence of the specific heat and the anisotropic features in the magnetic susceptibility and magnetization have been analyzed on the basis of the crystalline electric field (CEF) model. The overall energy splitting of the CEF scheme in RRhIn5 is estimated to be in the range from 44 to 330 K. The magnetic properties are discussed on the basis of the sign of the CEF parameter.
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  • Naoki Ishimatsu, Hiroshi Maruyama, Naomi Kawamura, Motohiro Suzuki, Ya ...
    2007 Volume 76 Issue 6 Pages 064703
    Published: June 15, 2007
    Released on J-STAGE: August 12, 2010
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    The stability of the ferromagnetic state in Fe, Co, and Ni metals under high pressure is studied using X-ray magnetic circular dichroism (XMCD) at the K-edge and X-ray powder diffraction. It is found that the ferromagnetic state under pressure is very different for Fe, Co, and Ni metals, and is closely associated with the crystal structure. In the case of Fe, the XMCD spectrum disappears with increasing pressure from 14.2 to 17.8 GPa, indicating the transition from a ferromagnetic to a nonmagnetic state. This transition results in the bcc→hcp martensitic transformation accompanied by a decrease in the ca ratio of the hcp phase. In contrast to Fe, the dichroic amplitude in Co and Ni decreases slightly under the applied pressure. The ferromagnetic states in Co and Ni metals are maintained even at 39 and 48 GPa, respectively. The stability of ferromagnetism is interpreted from the viewpoint of electronic states.
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  • Hirofumi Mino, Ayumu Kobayashi, Grzegorz Karczewski, Tomasz Wojtowicz, ...
    2007 Volume 76 Issue 6 Pages 064704
    Published: June 15, 2007
    Released on J-STAGE: August 12, 2010
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    Exciton and biexciton states in a CdMnTe/CdTe/CdMgTe quantum well were investigated by means of polarization-dependent four-wave mixing (FWM) measurements in magnetic fields up to 7 T. In co-linear and cross-linear polarization geometry, the FWM signals were strongly modified by the magnetic field, which was directed normal to the quantum-well plane. Very clear beat structures due to giant Zeeman splitting of the excitons were observed. In the co-circular (σ+,σ+) configuration, a high magnetic field induced a beat-like structure in an early delay-time region. Spectrally resolved FWM signals indicating an additional transition appeared at the 1.1 meV higher energy side of the exciton resonance. According to the spin selection rule, the oscillator strength of the triplet biexciton that consisted of two σ+ excitons was found to increase in magnetic fields.
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  • Kenjiro Hashi, Naohito Tsujii, Tadashi Shimizu, Atsushi Goto, Shinobu ...
    2007 Volume 76 Issue 6 Pages 064705
    Published: June 15, 2007
    Released on J-STAGE: August 12, 2010
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    51V-NMR measurements of the Haldane compound PbNi2V2O8 at 30 T have been performed by using a hybrid magnet installed at National Institute for Materials Science. The NMR spectrum begins to split at 12 K with decreasing temperature. The temperature at which the NMR spectrum begins to split well agrees with the temperature at which the magnetization takes the minimum. The splitting of the NMR spectrum gives microscopic evidence for the presence of the field-induced antiferromagnetic ordering. The splitting has grown uniformly with decreasing temperature, suggesting that the transition is of second order and the magnitude of the ordered moment is uniform. The upper limit of the magnitude of the ordered moment was estimated from dipole field calculations.
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  • Keishi Kanada, Takehiro Saito, Akira Oosawa, Takayuki Goto, Takao Suzu ...
    2007 Volume 76 Issue 6 Pages 064706
    Published: June 15, 2007
    Released on J-STAGE: August 12, 2010
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    The antiferromagnetic ordering in the solid-solution of the two spin-gap systems (CH3)2CHNH3CuCl3 and (CH3)2CHNH3CuBr3 has been investigated by 1H-NMR. The sample with the Cl-content ratio x=0.85 showed a clear splitting in spectra below TN=13.5 K, where the spin–lattice relaxation rate T1−1 showed a diverging behavior. The critical exponent of the temperature dependence of the hyperfine field is found to be 0.33.
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  • Junya Otsuki
    2007 Volume 76 Issue 6 Pages 064707
    Published: June 15, 2007
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    The Anderson model with the Coulomb interaction between the local and conduction electrons is studied in the semiconducting phase. Based on a perturbation theory from the atomic limit, leading contributions for the c–f Coulomb interaction are incorporated as a vertex correction to hybridization. An analytical solution shows that the effective attraction in the intermediate states leads to a bound state localized at the local electron site. Self-consistent equations are constructed as an extension of the non-crossing approximation (NCA) to include the vertex part yielding the bound state. A numerical calculation demonstrates the excitonic bound state inside the semiconducting gap for single-particle excitations, and a discontinuity at the gap edge for magnetic excitations.
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  • Hiroto Adachi, Predrag Miranovic, Masanori Ichioka, Kazushige Machida
    2007 Volume 76 Issue 6 Pages 064708
    Published: June 15, 2007
    Released on J-STAGE: August 12, 2010
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    To see how superconducting gap structures affect the longitudinal component of mixed-state thermal conductivity κxx(B), the magnetic-field dependences of κxx(B) in s- and d-wave superconductors are investigated. Calculations are performed on the basis of the quasi-classical theory of superconductivity by fully taking account of the spatial variation of the normal Green’s function, neglected in previous works, by the Brandt–Pesch–Tewordt approximation. On the basis of our result, we discuss the possibility of κxx(B) measurement as a method of probing the gap structure.
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  • Ryusuke Ikeda
    2007 Volume 76 Issue 6 Pages 064709
    Published: June 15, 2007
    Released on J-STAGE: August 12, 2010
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    The electric conductivities in glass phases of three-dimensional (3D) granular superconductors in magnetic fields are examined based on a disordered quantum Josephson-junction array. Contrary to a recent argument of a glass phase with metallic response, a correct inclusion of an Ohmic dissipative dynamics always leads to a glass phase with divergent dc conductivity. With no dissipative term, a metallic glass phase is obtained irrespective of the range of correlation of quenched disorder, i.e., even in the so-called Bose-glass phase with experimentally vanishing resistivity.
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  • Isao Kagomiya, Yoshiaki Hata, Daisuke Eto, Hideto Yanagihara, Eiji Kit ...
    2007 Volume 76 Issue 6 Pages 064710
    Published: June 15, 2007
    Released on J-STAGE: August 12, 2010
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    It was disclosed that both magnetic field along the ⟨111⟩ and pressure along the ⟨100⟩, applied during cooling of a ZnCr2O4 single crystal through TN, affect the intensities of magnetic peaks of neutron diffraction below TN. Magnetic field along the ⟨100⟩ axis have no effect on the magnetic intensities. This fact indicates that the magnetic symmetry of the low temperature phase of ZnCr2O4 is monoclinic or lower.
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  • Yasunori Kubo, Yoshiharu Sakurai, Masayoshi Ito, Akihisa Koizumi, Kazu ...
    2007 Volume 76 Issue 6 Pages 064711
    Published: June 15, 2007
    Released on J-STAGE: August 12, 2010
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    The electron momentum densities of the layered transition metal trichalcogenide ZrTe3 have been studied by high-resolution Compton profiles (CPs) along the a*, b*, and c* directions, together with the theoretical CPs calculated using the local-density approximation based full-potential linearized augmented plane wave method. A fairly good accord between theory and experiment is found with respect to the overall shapes of the CPs and the anisotropies in the CPs defined as differences between pairs of various CPs. The observed anisotropy between b* and c* directions is much smaller compared with the others, in agreement with the theoretical result. It is shown that the Fermi surface geometry plays an effective role to reproduce the anisotropies. The characteristics of the Fermi surfces and bonding conditions in the ZrTe3 are examined, and insights of the features in the CPs are gained.
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  • Tatsuma D. Matsuda, Yoshinori Haga, Etsuji Yamamoto, Shugo Ikeda, Hiro ...
    2007 Volume 76 Issue 6 Pages 064712
    Published: June 15, 2007
    Released on J-STAGE: August 12, 2010
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    We succeeded in growing a high-quality single crystal of ThRhIn5 with the HoCoGa5-type tetragonal crystal structure by the In-flux method. The lattice parameters, positional parameters and thermal parameters were determined from single-crystal x-ray diffraction measurements. We also measured the electrical resistivity and de Haas–van Alphen (dHvA) effect. Main dHvA branches are very similar to those of the 4f-itinerant heavy fermion superconductor CeCoIn5, but the cyclotron effective masses are by one to two orders of magnitude smaller than those of CeCoIn5. These Fermi surface properties are well explained by the FLAPW energy band calculations.
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  • Hideki Kumazaki, Dai S. Hirashima
    2007 Volume 76 Issue 6 Pages 064713
    Published: June 15, 2007
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    It is shown that a strong impurity potential induces short-range antiferromagnetic (ferrimagnetic) order around itself in a Hubbard model on a half-filled honeycomb lattice. This implies that short-range magnetic order is induced in monolayer graphene by a nonmagnetic defect such as a vacancy with full hydrogen termination or a chemisorption defect.
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  • Yusuke Nishikayama, Tatsuya Shishidou, Tamio Oguchi
    2007 Volume 76 Issue 6 Pages 064714
    Published: June 15, 2007
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    The electronic and structural properties of Y2C3 are studied from first principles. We optimize all the structural parameters, the lattice constant and internal atomic positions, assuming the observed crystal structure symmetry. We also examine the lattice-constant and the C dimer bond length dependences of the electronic properties of Y2C3. It is found that there is a peak structure in close vicinity to the Fermi energy in the density of states for the optimized structure at all the lattice constants studied. This peak structure comes from a flat band along ΓN line.
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  • Toshikazu Nakamura, Ko Furukawa, Toshifumi Hara
    2007 Volume 76 Issue 6 Pages 064715
    Published: June 15, 2007
    Released on J-STAGE: August 12, 2010
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    13C nuclear magnetic resonance (NMR) investigations were carried out for a one-dimensional organic conductor, (TMTTF)2PF6, to determine the charge dynamics and configuration in the proximity of the spin-Peierls phase-transition temperature, TsP. Although no obvious NMR line splitting associated with the charge-ordering transitions in the intermediate paramagnetic states was observed, the charge separation amplitude was estimated to be ρCO∼0.14 using the 13C NMR spin–lattice relaxation rates for the distinct lines. The abrupt decrease in the NMR linewidth below 25 K and the small anisotropy of the NMR linewidth in the spin-Peierls phase indicate the possible redistribution of the charge separation in the proximity of TsP. The low-temperature electronic states of (TMTTF)2PF6 are discussed from a microscopic point of view.
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  • Suguru Ikeda, Masafumi Sera, Shingo Hane, Yoshiya Uwatoko, Masashi Kos ...
    2007 Volume 76 Issue 6 Pages 064716
    Published: June 15, 2007
    Released on J-STAGE: August 12, 2010
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    The effect of pressure on CeB6 was investigated by the measurement of the magnetization (M) under pressure, and we obtained the following results. The effect of pressure on M in phase I is very small. By applying pressure, TQ is enhanced, but TN and the critical field from the antiferromagnetic (AFM) phase III to the antiferro-quadrupole (AFQ) phase II (HcIII–II) are suppressed, as previously reported. The magnetization curve in phase III shows the characteristic shoulder at HHcIII–II⁄2 at ambient pressure. This shoulder becomes much more pronounced by applying pressure. Both HcIII–II and the magnetic field, where a shoulder is seen in the magnetization curve in phase III, are largely suppressed by pressure. In phase II, the MT curve at a low magnetic field exhibits an unusual concave temperature dependence below TQ down to TN. Thus, we found that the lower the magnetic field, the larger the enhancement of M in both phases III and II. To clarify the origin of the unusual pressure effect of M, we performed a mean-field calculation for the 4-sublattice model using the experimental results of dTQdP>0 and dTNdP<0 and assuming the positive pressure dependence of the Txyz-antiferro-octupole (AFO) interaction. The characteristic features of the pressure effect of M obtained by the experiments could be reproduced well by the mean-field calculation. We found that the origin of the characteristic effect of pressure on CeB6 is the change in the subtle balance between the AFM interaction and the magnetic field-induced-effective FM interaction induced by the coexistence of the Oxy–AFQ and Txyz–AFO interactions under pressure.
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  • Hiroshi Isoda, Akira Sakai, Riki Kawashima
    2007 Volume 76 Issue 6 Pages 065001
    Published: June 15, 2007
    Released on J-STAGE: August 12, 2010
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  • Shun Tonooka, Hiroki Nakano, Koichi Kusakabe, Naoshi Suzuki
    2007 Volume 76 Issue 6 Pages 065002
    Published: June 15, 2007
    Released on J-STAGE: August 12, 2010
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  • Satoshi Tsutsui, Yoshitaka Yoda, Hisao Kobayashi
    2007 Volume 76 Issue 6 Pages 065003
    Published: June 15, 2007
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  • Ichiro Tamura, Tsuyoshi Ikeno, Toshio Mizushima, Yosikazu Isikawa
    2007 Volume 76 Issue 6 Pages 065004
    Published: June 15, 2007
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  • Takafumi Kita
    2007 Volume 76 Issue 6 Pages 067001
    Published: June 15, 2007
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  • Noriki Terada, Yoshikazu Tanaka, Yoshikazu Tabata, Koichi Katsumata, A ...
    2007 Volume 76 Issue 6 Pages 068001
    Published: June 15, 2007
    Released on J-STAGE: August 12, 2010
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