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Volume 73, Issue 11
Displaying 1-50 of 52 articles from this issue
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Noriko Oikawa, Yoshiki Hidaka, Shoichi Kai2004 Volume 73 Issue 11 Pages 2917-2920
Published: November 15, 2004
Released on J-STAGE: July 25, 2007
JOURNAL RESTRICTED ACCESSThe transition to turbulence in an electroconvective system of nematics separated by domain walls of the in-plane director is studied by observing the temporal change in image intensity. The measured time series are analyzed by the sonogram method. In the system where the domain structure is formed by abnormal roll instability, defect chaos appears as intermittent periodic oscillation limited by the domain walls. By increasing applied voltage, a periodic defect lattice appears. In the higher voltage region, the defect lattice collapses and changes into local turbulent states. The spatiotemporal intermittency is observed through these local turbulent domain motions.View full abstractDownload PDF (172K) -
K. Itoh, K. Hallatschek, S. Toda, H. Sanuki, S.-I. Itoh2004 Volume 73 Issue 11 Pages 2921-2923
Published: November 15, 2004
Released on J-STAGE: July 25, 2007
JOURNAL RESTRICTED ACCESSThe nonlinear structure of the zonal flow in toroidal plasma is investigated in the case that the autocorrelation times of drift waves are much shorter than the autocorrelation time of zonal flow. It is found that the turbulent drive of the zonal flow starts to decrease at a high velocity shear of the zonal flow. By this mechanism, the zonal flow evolves into a stable stationary structure in turbulent plasmas. Flow velocity and radial wavelength are obtained.View full abstractDownload PDF (88K) -
Masao Arai, Takafumi Kita2004 Volume 73 Issue 11 Pages 2924-2927
Published: November 15, 2004
Released on J-STAGE: July 25, 2007
JOURNAL RESTRICTED ACCESSWe report on the quantitative calculations of the upper critical field Hc2 for clean type-II superconductors Nb, NbSe2, and MgB2 within the weak-coupling theory. The Fermi surface anisotropy is fully taken into account by the energy band data from ab initio electronic structure calculations. The results for Nb and NbSe2 excellently reproduce both temperature and directional dependences of measured Hc2 curves without any adjustable parameters, including a marked upward curvature of NbSe2 near Tc. As for MgB2, a good fit is obtained for a π⁄σ gap ratio of ∼0.3, which is close to that from a first-principles strong-coupling theory [H. J. Choi et al: Nature 418 (2002) 758]. Our results indicate the importance of Fermi surface anisotropy in describing Hc2.View full abstractDownload PDF (107K) -
Masahiro Hara, Akira Endo, Shingo Katsumoto, Yasuhiro Iye2004 Volume 73 Issue 11 Pages 2928-2931
Published: November 15, 2004
Released on J-STAGE: July 25, 2007
JOURNAL RESTRICTED ACCESSWe have investigated universal conductance fluctuations (UCF) in a narrow channel of two-dimensional electron gas subjected to a gradient magnetic field with a vanishing average, generated from a cobalt strip deposited along the center line of the channel. We find that the fluctuation amplitude ΔG tends to be a larger value in the low-temperature limit and the characteristic field Bc is less temperature sensitive, compared with those for UCF in a uniform magnetic field.View full abstractDownload PDF (251K) -
Toyohiko Kinoshita, Takanori Wakita, HaiLin Sun, Takahide Tohyama, Ayu ...2004 Volume 73 Issue 11 Pages 2932-2935
Published: November 15, 2004
Released on J-STAGE: July 25, 2007
JOURNAL RESTRICTED ACCESSAntiferromagnetic (AFM) domain structures of a NiO(100) surface have been observed using a combined method of photoelectron emission microscopy (PEEM) and soft-X-ray linear dichroism (LD) at an O K edge. Since oxygen atoms in NiO crystal should not have any magnetic moment, this imaging result was unexpected. By evaporating the magnetic materials (Fe) on the NiO crystal, the observed domain structure of NiO at a Ni L edge was strongly affected by the exchange coupling between the magnetic thin film and the AFM substrate, whereas that at the O K edge was not. It is concluded from these results that the LD at the O K edge originates from the anisotropy due to the strong coupling with the Ni 3d orbital. The observed image at the O K edge reflects essentially the T-domain information concerning the AFM crystal distortion. In contrast, the domain structure observed at the Ni L edge seems to show both T- and S-domain patterns.View full abstractDownload PDF (149K) -
C. W. Chiu, F. L. Shyu, C. P. Chang, D. S. Chuu, M. F. Lin2004 Volume 73 Issue 11 Pages 2936-2939
Published: November 15, 2004
Released on J-STAGE: July 25, 2007
JOURNAL RESTRICTED ACCESSThe excited conduction electrons in metallic armchair carbon nanotubes can decay by inelastic electron–electron scattering. The deexcitation channels include the single-particle and collective excitations of different angular momenta. The higher conduction subbands have more deexcitation channels, or shorter electron lifetimes. Each conduction subband has certain states with very long lifetimes, and a simple relationship between the inverse electron lifetime and the state energy is absent. Such results directly reflect the characteristics of the 1D excitation spectra. The inverse electron lifetime contrasts sharply with those of semiconducting carbon nanotubes, graphite, and 2D and 3D metallic systems. Dimensionalities play an important role in the many-body effects. The predicted results could be verified by femtosecond time-resolved optical spectroscopy.View full abstractDownload PDF (257K) -
Hironori Sakai, Yo Tokunaga, Shinsaku Kambe, Kentaro Kitagawa, Hiroshi ...2004 Volume 73 Issue 11 Pages 2940-2943
Published: November 15, 2004
Released on J-STAGE: July 25, 2007
JOURNAL RESTRICTED ACCESS111Cd NMR measurements have been performed in the superconducting (SC) state of the pyrochlore Cd2Re2O7 at Tc∼1 K, and in a field of less than 3 kOe below Tc. The upper critical field at 0.1 K has been determined to be 4 kOe from in situ measurements of the ac susceptibility. A reduction of the Knight shift in the SC state is confirmed. The present results provide strong evidence that this compound has a singlet SC pairing symmetry.View full abstractDownload PDF (198K) -
Ryosuke Kadono, Kazuki Ohishi, Akihiro Koda, Wataru Higemoto, Kenji M. ...2004 Volume 73 Issue 11 Pages 2944-2947
Published: November 15, 2004
Released on J-STAGE: July 25, 2007
JOURNAL RESTRICTED ACCESSWe report the local magnetic response of an electron-doped cuprate superconductor, Pr0.89LaCe0.11CuO4−y (Tc\\simeq26 K), studied by muon spin rotation (μSR) over a field range from 200 Oe to 50 kOe. In the paramagnetic state, the muon Knight shift along the crystal c-axis (Kμz) is proportional to the in-plane susceptibility χab. More surprisingly, Kμz is strongly enhanced by the occurrence of superconductivity (below ∼40 kOe), changing its sign from positive to negative around ∼1 kOe with increasing field. This finding can be understood by considering the weak polarization of Pr ions due to the superexchange interaction with the antiferromagnetic Cu sublattice, which coexists with superconductivity.View full abstractDownload PDF (143K) -
Hiroshi N. Kono, Katsunori Kubo, Yoshio Kuramoto2004 Volume 73 Issue 11 Pages 2948-2951
Published: November 15, 2004
Released on J-STAGE: July 25, 2007
JOURNAL RESTRICTED ACCESSA minimal model for multipole orders in CeB6 shows that the degeneracy of the quadrupole order parameters and strong spin–orbit coupling lead to peculiar temperature and magnetic-field dependences of the X-ray reflection intensity at superlattice Bragg points. Furthermore, the intensity depends sensitively on the surface direction. These theoretical results explain recent X-ray experiments in phases II and III of CeB6. It is predicted that under weak magnetic fields perpendicular to the (111) surface, reflection intensity should change nonmonotonically as a function of temperature.View full abstractDownload PDF (254K) -
Kazuhide Kenmochi, Van Ann Dinh, Kazunori Sato, Akira Yanase, Hiroshi ...2004 Volume 73 Issue 11 Pages 2952-2954
Published: November 15, 2004
Released on J-STAGE: July 25, 2007
JOURNAL RESTRICTED ACCESSWe propose materials design to fabricate a new class of diluted magnetic semiconductors (DMSs) based on MgO, SrO and BaO without magnetic elements. Replacing the oxygen atoms by other atoms such as C atoms leads to the induction of a deep-impurity band. These materials show ferromagnetic behaviour if the impurity-band width (W) and the electron-correlation energy (U) satisfy the conditions of a highly correlated electron system (U>W). Based on first-principles calculations, we demonstrate that these materials could satisfy Stoner’s condition, and could be new candidates for transparent and half-metallic ferromagnetic DMSs without any magnetic elements.View full abstractDownload PDF (127K) -
Akiko Kikkawa, Koichi Katsumata, Shuji Ebisu, Shoichi Nagata2004 Volume 73 Issue 11 Pages 2955-2958
Published: November 15, 2004
Released on J-STAGE: July 25, 2007
JOURNAL RESTRICTED ACCESSMagnetic susceptibility, magnetization and heat capacity measurements are performed on a single crystal sample of α-Gd2S3. From the heat capacity measurements, we find a sharp anomaly at \\simeq10 K signaling the onset of a long-range magnetic order. We find that a large amount of heat capacity remains below the transition temperature. The magnetization along the b axis at low temperatures shows a steep increase at about 2 T followed by a second increase at about 4.5 T. From these measurements a magnetic field versus temperature phase diagram is constructed, where three magnetically ordered phases are found. These experimental results are discussed in the context of magnetic frustration.View full abstractDownload PDF (445K) -
Shigeo Hara, Yoshiyuki Yoshida, Shin-Ichi Ikeda, Naoki Shirakawa, Mich ...2004 Volume 73 Issue 11 Pages 2959-2962
Published: November 15, 2004
Released on J-STAGE: July 25, 2007
JOURNAL RESTRICTED ACCESSWe report the results of measurements of the magnetic properties of single-crystal of the normal spinel GeNi2O4 grown by a floating zone method. The crystal structure is face-centered cubic with a space group of Fd3m, which is the same structure as that of the well-known geometric frustrated heavy-mass Fermi liquid LiV2O4. Highly insulating antiferromagnetic GeNi2O4 possesses two Néel temperatures (TN1 and TN2) of 12.1 and 11.4 K without a structural phase transition. Ni2+ ions with integer spin (S=1) are located on the vertices of a three-dimensional network of corner-sharing tetrahedra. In this study, we show the magnetic susceptibility of GeNi2O4 to a magnetic field swept from the direction of ⟨100⟩ to ⟨110⟩ via ⟨111⟩. Below the transition temperatures, the field dependence of the magnetization, M(H), reveals field-induced magnetic anisotropy.View full abstractDownload PDF (270K) -
Magnetic Fluctuations in the Metallic State of Na0.7CoO2 Revealed by 23Na Nuclear Magnetic ResonanceYoshihiko Ihara, Kenji Ishida, Chishiro Michioka, Masaki Kato, Kazuyos ...2004 Volume 73 Issue 11 Pages 2963-2966
Published: November 15, 2004
Released on J-STAGE: July 25, 2007
JOURNAL RESTRICTED ACCESSNuclear magnetic resonance (NMR) studies were performed on Na0.7CoO2 to investigate its magnetic properties from the microscopic viewpoint. Na0.7CoO2 is a starting compound of the recently discovered superconductor Na0.35CoO2·1.3H2O, in which Co atoms form a triangular structure. Although 23Na NMR results show no magnetic anomaly down to 1.5 K, Knight shift (23K) and 23(1⁄T1T) of 23Na continue to increase, suggestive of the vicinity of the magnetic phase. From the relation between 23K and 23(1⁄T1T), it is shown that ferromagnetic fluctuations are dominant below 100 K. In addition to ferromagnetic correlations, antiferromagnetic fluctuations are found develop to in a low-temperature region below 4 K. Magnetic fluctuations considered from our experiment are discussed.View full abstractDownload PDF (179K) -
Takeshi Matsumura, Hideaki Ishida, Taku J. Sato, Kenichi Katoh, Yuzuru ...2004 Volume 73 Issue 11 Pages 2967-2970
Published: November 15, 2004
Released on J-STAGE: July 25, 2007
JOURNAL RESTRICTED ACCESSAn inelastic neutron scattering experiment has been performed on a new heavy-fermion compound, YbAgGe, for a polycrystalline sample at zero magnetic field. A quasielastic scattering and a crystal field excitation at 12 meV are observed. Both are broadened due to the Kondo effect with an intrinsic width of 0.9 meV at 1.5 K, which increases to about 3 meV at 300 K. The temperature dependence follows Γ0+A\\sqrtT typically observed in Kondo systems. Crystal field parameters are also deduced. To explain the result that only one excitation is observed at 12 meV, the B22 term is assumed as the main component.View full abstractDownload PDF (153K) -
Hiroyuki Nakamura, Saurav Giri, Takao Kohara2004 Volume 73 Issue 11 Pages 2971-2974
Published: November 15, 2004
Released on J-STAGE: July 25, 2007
JOURNAL RESTRICTED ACCESSExperimental results of the susceptibility, the Knight shift and the nuclear spin–lattice relaxation rate suggest that the tetragonal intemetallic compound with linear chains of Mn atoms, YMn4Al8, has a narrow pseudogap in the spin excitation spectrum. This compound may be another candidate of a 3d transition metal compound with a correlated gap similar to FeSi.View full abstractDownload PDF (130K) -
Jong-Hoon Huh, Yoichi Akasako, Shoichi Kai2004 Volume 73 Issue 11 Pages 2975-2978
Published: November 15, 2004
Released on J-STAGE: July 25, 2007
JOURNAL RESTRICTED ACCESSWe report electroconvection in a cholesteric liquid crystal with negative dielectric anisotropy, that is, a mixture of p-methoxy benzilidene p-n-butylaniline (MBBA) with a small amount of a cholesteric dopant cholesteryl nonanoate (CN). By changing the corresponding helical pitch by varying the concentration of CN, a variety of ac-driven convective patterns are found in sandwiched sample cells. The pitch and temperature dependences of their threshold voltages and characteristic wavelength of the patterns are systematically investigated.View full abstractDownload PDF (171K) -
Ambarish Kunwar, Alexander John, Katsuhiro Nishinari, Andreas Schadsch ...2004 Volume 73 Issue 11 Pages 2979-2985
Published: November 15, 2004
Released on J-STAGE: July 25, 2007
JOURNAL RESTRICTED ACCESSThe traffic-like collective movement of ants on a trail can be described by a stochastic cellular automaton model. We have earlier investigated its unusual flow–density relation by using various mean field approximations and computer simulations. In this paper, we study the model following an alternative approach based on the analogy with the zero range process, which is one of the few known exactly solvable stochastic dynamical models. We show that our theory can quantitatively account for the unusual non-monotonic dependence of the average speed of the ants on their density for finite lattices with periodic boundary conditions. Moreover, we argue that the model exhibits a continuous phase transition at the critial density only in a limiting case. Furthermore, we investigate the phase diagram of the model by replacing the periodic boundary conditions by open boundary conditions.View full abstractDownload PDF (167K) -
Taksu Cheon, Takaomi Shigehara2004 Volume 73 Issue 11 Pages 2986-2990
Published: November 15, 2004
Released on J-STAGE: July 25, 2007
JOURNAL RESTRICTED ACCESSThe standard Kronig–Penney model with periodic δ potentials is extended to the cases with generalized contact interactions. The eigen equation which determines the dispersion relation for one-dimensional periodic array of the generalized contact interactions is deduced with the transfer matrix formalism. Numerical results are presented which reveal unexpected band spectra with broader band gap in higher energy region for generic model with generalized contact interaction.View full abstractDownload PDF (99K) -
Engui Fan2004 Volume 73 Issue 11 Pages 2991-2995
Published: November 15, 2004
Released on J-STAGE: July 25, 2007
JOURNAL RESTRICTED ACCESSBy introducing a q-deformed spectral problem, we derive a new generalized q-KdV hierarchy with variable coefficients. Darboux matrix technique is further extended to construct an explicit and universal Darboux transformation for the q-KdV hierarchy. It is found that the Darboux transformation admits a theorem of permutability theorem and a superposition formula. In particular, the soliton-like solutions whose speeds may depend on time variable t are obtained by applying the Darboux transformation and superposition formula.View full abstractDownload PDF (94K) -
Jun’ichi Ieda, Takahiko Miyakawa, Miki Wadati2004 Volume 73 Issue 11 Pages 2996-3007
Published: November 15, 2004
Released on J-STAGE: July 25, 2007
JOURNAL RESTRICTED ACCESSFollowing our previous work [J. Ieda, T. Miyakawa and M. Wadati: cond-mat/0404569] on a novel integrable model describing soliton dynamics of an F=1 spinor Bose–Einstein condensate, we discuss in detail the properties of the multi-component system with spin-exchange interactions. The exact multiple bright soliton solutions are obtained for the system where the mean-field interaction is attractive (c0<0) and the spin-exchange interaction is ferromagnetic (c2<0). A complete classification of the one-soliton solution with respect to the spin states and an explicit formula of the two-soliton solution are presented. For solitons in polar state, there exists a variety of different shaped solutions including twin peaks. We show that a “singlet pair” density can be used to distinguish those energetically degenerate solitons. We also analyze collisional effects between solitons in the same or different spin state(s) by computing the asymptotic forms of their initial and final states. The result reveals that it is possible to manipulate the spin dynamics by controlling the parameters of colliding solitons.View full abstractDownload PDF (883K) -
Jun Sato, Masahiro Shiroishi, Minoru Takahashi2004 Volume 73 Issue 11 Pages 3008-3014
Published: November 15, 2004
Released on J-STAGE: July 25, 2007
JOURNAL RESTRICTED ACCESSTransition rates and dynamic spin structure factor at zero temperature for the spin-1⁄2 XXZ chain at critical regime in a magnetic field are numerically evaluated in terms of the exact determinant representations for the form factors and norms of the Bethe eigenstates. We have seen that the transition rates converges toward the constant function with the value 1 in the limit Δ→0. The observed critical exponent of the singularity at the lower boundary is compared with the one predicted from the comformal field theory. We confirm that they are in good agreement. Further we have discovered that a small peak emerges near the upper boundary in the line shape of S(q,ω) for 0<Δ<1.View full abstractDownload PDF (504K) -
Takeshi Nakatsubo, Shin-ichiro Nagasaka, Takehisa Yoshinari, Yoshio Ta ...2004 Volume 73 Issue 11 Pages 3015-3019
Published: November 15, 2004
Released on J-STAGE: July 25, 2007
JOURNAL RESTRICTED ACCESSOptical studies of a single anthracene molecule succeeded by using a β-cyclodextrin (CyD) as an isolating cage. The absorption and the fluorescence spectra consist of several vibronic lines with 0.174–0.178 eV intervals and are mirror image with each other. In addition, their line shapes vary scarcely between RT and 2 K. These facts indicate that the anthracene molecule is almost free in the β-CyD cage. These spectra are theoretically analyzed by a free-molecule-model in which the electronic excited state couples with the vibrations hω of the molecule with coupling strength s (Haung Rhys factor). Observed spectra are in good agreement with theoretical ones with s=1.56 and hω=0.178 eV. For the single crystal of anthracene, absorption and fluorescence were also measured. At 2 K, the zero-phonon peak becomes enhanced and the phonon lines becomes sharpened compared with the single molecule case. But at RT, the fluorescence spectrum becomes quite diffused shape. These facts suggest that the exciton can move among anthracene molecules at low temperatures. It falls into a trapped state at RT.View full abstractDownload PDF (178K) -
Masato Makino, Masao Doi2004 Volume 73 Issue 11 Pages 3020-3025
Published: November 15, 2004
Released on J-STAGE: July 25, 2007
JOURNAL RESTRICTED ACCESSWe present a theory to calculate the viscoelasticity of dilute suspensions of particles of general shape. We give a formula for the dynamic viscosity expressed in terms of the mobility tensors. We study the viscoelasticity of propeller-like particles which consist of two disks and thin-rod. The non-linear viscoelasticity and the normal stresse differences of the propeller-like particles are calculated by computer simulation.View full abstractDownload PDF (188K) -
Masato Ida2004 Volume 73 Issue 11 Pages 3026-3033
Published: November 15, 2004
Released on J-STAGE: July 25, 2007
JOURNAL RESTRICTED ACCESSThe theoretical results regarding the “transition frequencies” of two acoustically interacting bubbles have been verified numerically. The theory provided by Ida [Phys. Lett. A 297 (2002) 210] predicted the existence of three transition frequencies per bubble, each of which has the phase difference of π⁄2 between a bubble’s pulsation and the external sound field, while previous theories predicted only two natural frequencies which cause such phase shifts. Namely, two of the three transition frequencies correspond to the natural frequencies, while the remaining does not. In a subsequent paper [M. Ida: Phys. Rev. E 67 (2003) 056617], it was shown theoretically that transition frequencies other than the natural frequencies may cause the sign reversal of the secondary Bjerknes force acting between pulsating bubbles. In the present study, we employ a direct numerical simulation technique that uses the compressible Navier–Stokes equations with a surface-tension term as the governing equations to investigate the transition frequencies of two coupled bubbles by observing their pulsation amplitudes and directions of translational motion, both of which change as the driving frequency changes. The numerical results reproduce the recent theoretical predictions, validating the existence of the transition frequencies not corresponding to the natural frequency.View full abstractDownload PDF (357K) -
Hidekazu Tsuji, Masayuki Oikawa2004 Volume 73 Issue 11 Pages 3034-3043
Published: November 15, 2004
Released on J-STAGE: July 25, 2007
JOURNAL RESTRICTED ACCESSTwo-dimensional interaction of two solitary waves is investigated numerically on the basis of a Modified Kadomtsev–Petviashvili equation. Two types of interaction are dealt with; one is the interaction of two positive solitary waves of an equal amplitude and the other is that between positive and negative solitary waves of an equal amplitude. The latter turns out to be considerably different from the former. In both cases the characteristics of the interaction depend on the ratio of a parameter representing the difference of the propagation directions of two solitary waves to the amplitude of the solitary waves. It is found that a new wave of a fairly large amplitude is produced for some range of the ratio as a result of the interaction of two positive solitary waves.View full abstractDownload PDF (760K) -
M. K. Salem, F. M. Aghamir, B. Sh. Sabzevari, M. Ghoranneviss2004 Volume 73 Issue 11 Pages 3044-3050
Published: November 15, 2004
Released on J-STAGE: July 25, 2007
JOURNAL RESTRICTED ACCESSThe propagation of electromagnetic waves in a two dimensional inhomogeneous plasma and applied magnetic field is studied. The generalized eikonal equations along with two dimensional Hamiltonian equations are used to reach at a system of transport equations for two separate modes. The reflection of electromagnetic waves in a direction perpendicular to the applied magnetic field, as a mean of mode coupling, is investigated. Application of this model to a simple practical example is presented to check its merit. It is found that the difference of this approach with the one dimensional case is in the number of cut off points wave encounters.View full abstractDownload PDF (110K) -
C.-H. Yang, J. H. Song, S. H. Park, Y. N. Choi, C.-H. Lee, Y. H. Jeong2004 Volume 73 Issue 11 Pages 3051-3058
Published: November 15, 2004
Released on J-STAGE: July 25, 2007
JOURNAL RESTRICTED ACCESSWe investigated the structural phase transition occurring around 760 K in a colossal magnetoresistance material, La0.625Ca0.375MnO3. In order to uncover detailed features of this transition between the high temperature rhombohedral (R\\bar3c) and the low temperature orthorhombic phase (Pnma), high resolution neutron powder diffraction, resistivity measurements, and elastic constant measurements were carried out up to 1000 K. From the Rietveld refinement analysis of the powder diffraction data, it is shown that the transition is of first order as expected from symmetry and that there exists a temperature region of ∼40 K around the transition temperature where the two phases coexist. This phase coexistence in the transition region accounts for the results of the elastic constant and resistivity measurements. Neutron powder diffraction data also allowed us to determine the tilt angles of the soft lattice modes, R25 and M3, relevant to the phase transition.View full abstractDownload PDF (1239K) -
Shin Nakamura, Susumu Shimomura, Naoshi Ikeda, Shigeki Nimori, Takao T ...2004 Volume 73 Issue 11 Pages 3059-3063
Published: November 15, 2004
Released on J-STAGE: July 25, 2007
JOURNAL RESTRICTED ACCESSStructural feature of Eu0.6Sr0.4MnO3 through the magnetic-field-induced insulator-to-metal (IM) transition has been investigated by X-ray powder diffraction in a magnetic field using synchrotron radiation. No superlattice reflections due to the charge and orbital ordering are detected in the insulator phase down to 20 K. Both of the insulator phase and the induced metal phase are proved to be in orthorhombic structure with Pnma space group, and thus a change of the crystal symmetry is not detected on the IM transition. However, the lattice constants abruptly increase and the reflection intensities abruptly change through the transition. These suggest a rotation of MnO6 octahedron in a manner to increase Mn–O–Mn angles. This structural change is consistent with a gain in electron transfer energy in the double exchange mechanism that stabilizes the metallic and ferromagnetic state.View full abstractDownload PDF (449K) -
Yo Machida, Takayasu Hanashima, Koichi Ohkubo, Kouji Yamawaki, Masahik ...2004 Volume 73 Issue 11 Pages 3064-3069
Published: November 15, 2004
Released on J-STAGE: July 25, 2007
JOURNAL RESTRICTED ACCESSThe thermal diffuse scattering of synchrotron x-rays was measured for a single crystal of 1T-TaS2 along high symmetry direction in reciprocal space within the temperature range of 300–460 K. Least-squares analysis in terms of a lattice dynamics yielded phonon dispersion curves. The dispersion curves revealed Kohn anomalies both in a longitudinal acoustic (LA) mode and transverse acoustic (TA||) mode polarized along b* direction. The results show that the softened TA|| modes trigger the rotation of the ordering vector in the nearly commensurate phase at low temperature.View full abstractDownload PDF (209K) -
Mitsuo Machida, Toku Ishibashi2004 Volume 73 Issue 11 Pages 3070-3077
Published: November 15, 2004
Released on J-STAGE: July 25, 2007
JOURNAL RESTRICTED ACCESSIn order to study the phase transition in (CH3)3NCH2COO·H3PO4 (BP) at 365 K, crystal structure was re-determined at 373 K (phase I) and 298 K (phase II) by single-crystal neutron diffraction. In addition, temperature dependences of the 043 and \\bar531 structure factors were examined in phase II. In the structure determination, reliability factor was converged at R=0.055 for 1089 reflections in phase II and at R=0.091 for 512 reflections in phase I. In phase II with the space group P21⁄c(Z=4), two independent protons in the quasi-one-dimensional hydrogen bond chain of the PO4 groups aligned along the b direction are disordered over two sites with distances 0.44 and 0.52 Å. The betaine (CH3)3NCH2COO connects to the hydrogen bond chain by forming two further hydrogen bonds. As for two protons involved in the hydrogen bonds linking the betaine and chain, one is partially ordered between two sites with occupation probabilities 0.67 and 0.33, while another orders at an off-center position of the hydrogen bond displaced toward the phosphate oxygen. In phase I with the space group P21⁄m(Z=2), the betaine and PO4 group undergo a disorder over two orientations intersecting the mirror plane perpendicular to the b axis. The molecular orientations in the asymmetric structure unit of phase I agree almost with those of phase II, and the ordering pattern appeared in phase II is antiferroelectric both along the b and c directions. Assuming that eight formula units behave as a unit of the disorder, the temperature dependences of the 043 and \\bar531 structure factors were analyzed by the quasi-one-dimensional Ising model. The Ising model reproduces quite well the behavior of the 043 and \\bar531 structure factors in the wide temperature region of phase II. The interaction parameters for intrachain J|| and interchain J⊥ are determined to be 1197 and 0.260 K from the 043 structure factor, respectively.View full abstractDownload PDF (251K) -
Hiroaki Ogawa, Fumihiko Saito, Michisuke Kobayashi2004 Volume 73 Issue 11 Pages 3078-3082
Published: November 15, 2004
Released on J-STAGE: July 25, 2007
JOURNAL RESTRICTED ACCESSA multi-component lattice gas model is introduced into superionic conductors. Using the model, the ionic conductivity in superionic conductors with two kinds of mobile ions is investigated. The Hamiltonian includes a repulsive interaction term and a weak hopping term for describing the interacting-ion system. It is shown that the ionic conductivity does not vary linearly with the fraction substituted and it has the minimum at an intermediate composition. This concentration dependence of the ionic conductivity qualitatively agrees with experiments performed for (AgxCu1−x)2Se.View full abstractDownload PDF (205K) -
Tomoya Isoshima, Martti M. Salomaa2004 Volume 73 Issue 11 Pages 3083-3086
Published: November 15, 2004
Released on J-STAGE: July 25, 2007
JOURNAL RESTRICTED ACCESSThe excitation spectrum and the band structure of a Bose–Einstein condensate in a periodic potential are investigated. Analyses within full 3D systems, finite 1D systems, and ideal periodic 1D systems are compared. We find two branches of excitations in the spectra of the finite 1D model. The band structures for the first and (part of) the second band are compared between a finite 1D and the fully periodic 1D systems, utilizing a new definition of an effective wavenumber and a phase-slip number. The upper and lower edges of the first gap coincide well between the two cases. The remaining difference is explained by the existence of the two branches due to the finite-size effect.View full abstractDownload PDF (660K) -
Hiroaki Katsuragi, Haruo Honjo2004 Volume 73 Issue 11 Pages 3087-3091
Published: November 15, 2004
Released on J-STAGE: July 25, 2007
JOURNAL RESTRICTED ACCESSWe argue differences between the Kardar–Parisi–Zhang with quenched disorder (KPZQ) and the ballistic deposition with power-law noise (BDP) models, using the multiaffine analysis method. The KPZQ and the BDP models show mono-affinity and multiaffinity, respectively. This difference results from the different distribution types of neighbor-height-differences in growth paths. Exponential and power-law distributions are observed in the KPZQ and the BDP, respectively. In addition, we point out the difference of profiles directly, i.e., although the surface profiles of both models and the growth path of the BDP model are rough, the growth path of the KPZQ model is smooth.View full abstractDownload PDF (254K) -
Yoshikazu Suzumura, Masato Isobe2004 Volume 73 Issue 11 Pages 3092-3098
Published: November 15, 2004
Released on J-STAGE: July 25, 2007
JOURNAL RESTRICTED ACCESSWe study one-dimensional density wave, which is pinned by impurity potential and commensurate potential at half-filling. The former pinning leads to Anderson glass (AG) state while the latter pinning results in Mott insulator (MI) state. The Mott glass (MG) state, which has been found in the classical case, is located between AG state and MI state, and exhibits a gap for a single particle excitation but no gap for the collective excitation. We examine the effect of quantum fluctuation on such a MG state by calculating a soliton-formation energy and an optical conductivity at low frequencies. The self-consistent harmonic approximation is applied to calculate the spring constant for the potential, which determines the magnitude of pinning frequency. It is found that the MG state still exists for small quantum fluctuation and that further increase of the fluctuation leads to the disappearance of the MG state due to the large reduction of the soliton-formation energy. The results are discussed in terms of the local distribution of pinning frequency.View full abstractDownload PDF (330K) -
A. Schenck, F. N. Gygax, M. S. Kim, T. Takabatake2004 Volume 73 Issue 11 Pages 3099-3107
Published: November 15, 2004
Released on J-STAGE: July 25, 2007
JOURNAL RESTRICTED ACCESSWe report on measurements of the Knight shift and relaxation behavior of spin polarized positive muons (μ+) implanted in monocrystalline CeRhSn. A two-component signal is seen below 100 K which appears to indicate the presence of two different types of domains or phases in which Ce is either in an intermediate, valence fluctuating state, occupying a volume fraction of ∼80% above 1.3 K, or in the 3+ ionic state, respectively. The latter domains become dominant below 0.5 K and can be partially suppressed by an external field Hext. The two associated Knight shifts and μSR line width’s as well as the bulk susceptibility χbulk reveal subtle changes at 30 K in the magnetic response. Strong anomalies, not present in χbulk, are seen in the two Knight shifts for Hext⊥c axis at ∼7 K. Some of the observed subtleties may originate from the conduction electron system. The small observed μSR line width’s are inconsistent with atomic disorder involved to explain certain non-Fermi liquid features. The absence of any kind of magnetic order is proven down to 50 mK.View full abstractDownload PDF (495K) -
Masafumi Tamura, Reizo Kato2004 Volume 73 Issue 11 Pages 3108-3110
Published: November 15, 2004
Released on J-STAGE: July 25, 2007
JOURNAL RESTRICTED ACCESSThe effective repulsive energy between the carriers in a molecular dimer has been examined in terms of the extended Hubbard model. The intermolecular Coulomb repulsion, V, rather than the intradimer transfer integral, t, has been shown to give major contribution to the effective repulsion in a strongly dimerized case. The effective repulsion of the dimer, as well as t, increases upon dimerization, for this reason. This analysis has been applied also to a two-level system, so that the strength of correlation is related to the structural features.View full abstractDownload PDF (96K) -
Senni Motomura, Shiro Kashimoto, Ryo Maezawa, Tsutomu Ishimasa, Susumu ...2004 Volume 73 Issue 11 Pages 3111-3114
Published: November 15, 2004
Released on J-STAGE: July 25, 2007
JOURNAL RESTRICTED ACCESSThe electrical resistivity of a recently discovered stable icosahedral quasicrystal Zn77Fe7Sc16 was found to have a T1⁄2 dependence in low temperature region between 2 and 16 K, while it increased gradually by 6.8% with the decrease in temperature from 270 to 2 K. The increase is considered to arise from the weak localization of conduction electrons. Negative magnetoresistance was found below 32 K. The T1⁄2 dependence of the resistivity and the negative magnetoresistance are interpreted on the basis of the short range magnetic order inferred from the spin-glass behavior.View full abstractDownload PDF (261K) -
Nobuhisa Fujita2004 Volume 73 Issue 11 Pages 3115-3120
Published: November 15, 2004
Released on J-STAGE: July 25, 2007
JOURNAL RESTRICTED ACCESSWe present a theoretical formulation of the one-electron problem constrained on the surface of a cylindrical tubule with varying diameter. Because of the cylindrical symmetry, we may reduce the problem to a one-dimensional equation for each angular momentum quantum number m along the cylindrical axis. The geometrical properties of the surface determine the electronic structures through the geometry dependent term in the equation. Magnetic fields parallel to the axis can readily be incorporated. Our formulation is applied to simple examples such as the catenoid and the sinusoidal tubules. The existence of bound states as well as the band structures, which are induced geometrically, for these surfaces are shown. To show that the electronic structures can be altered significantly by applying a magnetic field, Aharonov–Bohm effects in these examples are demonstrated.View full abstractDownload PDF (441K) -
Yuuichi Suginishi, Hiroshi Shimahara2004 Volume 73 Issue 11 Pages 3121-3128
Published: November 15, 2004
Released on J-STAGE: July 25, 2007
JOURNAL RESTRICTED ACCESSWe investigate the spin-triplet superconductivity mediated by phonons in quasi-one-dimensional (Q1D) systems with open Fermi surfaces. We obtain the ground state phase diagrams. It is found that spin-triplet superconductivity occurs for weak screening and strong on-site Coulomb interaction, even in the absence of any additional nonphonon pairing interactions. We find that the nodeless spin-triplet state is more favorable than the spin-triplet state with line nodes, for the parameter values of the Q1D superconductors (TMTSF)2X. We also find that Q1D open Fermi surface, which is the specific feature of this system, plays an essential role in the pairing symmetry. We discuss the compatibility of the present results with the experimental results in these compounds.View full abstractDownload PDF (224K) -
Teruhiko Akazawa, Hiroyuki Hidaka, Hisashi Kotegawa, Tatsuo C. Kobayas ...2004 Volume 73 Issue 11 Pages 3129-3134
Published: November 15, 2004
Released on J-STAGE: July 25, 2007
JOURNAL RESTRICTED ACCESSPressure-induced superconductivity is found in UIr without inversion symmetry. The pressure–temperature phase diagram has been investigated by means of the electrical resistivity and magnetization measurements under high pressure. The phase diagram consists of two magnetic phases, the Ising-like ferromagnetic phase (FM1) at low pressures and another magnetic phase (FM2) with the small ferromagnetic component along the [10\\bar1] direction at high pressures. Superconductivity is observed in the narrow pressure range near the disappearance point of the FM2 phase, where the temperature dependence of resistivity follows the non-Fermi liquid form of T1.6. From these experimental facts, the superconductivity is considered to be associated with the critical fluctuation with the disappearance of FM2 phase.View full abstractDownload PDF (743K) -
Akito Kobayashi, Shinya Katayama, Kouji Noguchi, Yoshikazu Suzumura2004 Volume 73 Issue 11 Pages 3135-3148
Published: November 15, 2004
Released on J-STAGE: July 25, 2007
JOURNAL RESTRICTED ACCESSWe theoretically examine superconductivity in quasi-two-dimensional organic conductor, α-(ET)2I3 salt, which has been found under uniaxial pressure and at temperature below the charge ordering. The interplay of many bands and several repulsive interactions gives rise to novel role of the charge ordering (CO), which leads to the coexistence with the superconducting (SC) state. The hole and electron pockets at Fermi surface, which exist in normal state and at ambient pressure, vanish in the charge ordered insulating state due to the formation of the charge gap. Under pressures, the charge gap disappears and the narrow gap semiconductor (NGS) with CO exhibits the density of state with a sharp peak just below the Fermi energy. Based on the mean field of CO state, charge and spin susceptibilities, and the paring interaction are evaluated by using the random phase approximation. The onset for the SC state is calculated in terms of a linearized Eliashberg equation, where the pairing interaction consists of both charge and spin fluctuations. The NGS results in the exotic SC state, which exhibits an extended s-state with large anisotropy of the gap. It is shown that the SC state is the inter-site pairing and is governed by the inter-site spin fluctuation.View full abstractDownload PDF (649K) -
Ping Huai, Yukihiro Shimoi, Shuji Abe2004 Volume 73 Issue 11 Pages 3149-3157
Published: November 15, 2004
Released on J-STAGE: July 25, 2007
JOURNAL RESTRICTED ACCESSControl of intramolecular spin alignment is studied theoretically in a model of polyene-based molecular magnets in which delocalized π electrons are coupled with localized radical spins. In a previous paper [Phys. Rev. Lett. 90 (2003) 207203], we have demonstrated that charge doping is an effective way to realize controllable high-spin in the π-conjugated molecular magnets. In this paper, we clarify the dependence of spin-alignment on the exchange interaction between the localized spin and π electron and the electron–electron interactions. The antiferromagnetic exchange interaction plays a role different from the ferromagnetic counterpart in doped molecules. To understand complex interplay of charge and spin degrees of freedom in the doped systems, we carry out a systematic study on the phase diagram of spin alignment in the parameter space. The mechanism of the spin alignment is discussed based on the spin densities of π electrons. The calculated results are consistent with experiments, providing a theoretical basis for the control of spin alignment.View full abstractDownload PDF (198K) -
Chun Ho Tsang, Khian-Hooi Chew, Yoshihiro Ishibashi, Franklin G. Shin2004 Volume 73 Issue 11 Pages 3158-3165
Published: November 15, 2004
Released on J-STAGE: July 25, 2007
JOURNAL RESTRICTED ACCESSWe studied the structure of interfaces in layered ferroelectrics comprising two different ferroelectric materials with first and/or second order transitions. The layered structure is described using the Landau–Ginzburg theory by including a bilinear coupling at the interface between the two neighboring layers. The interfacial coupling leads to the variation of polarization across the interface from one layer to another. An abrupt or continuous change of polarization across the interface is found to depend on the strength of coupling. For a layered structure having a layer in paraelectric phase, an interface-ordered state is predicted (in the paraelectric layer) as a manifestation of interfacial coupling. The Tilley–Zeks model is compared with the present approach to discuss the relationship between the bilinear coupling parameter and the extrapolation lengths.View full abstractDownload PDF (273K) -
Bold Gombojav, Takehisa Yoshinari, Hiroki Itoh, Shin-ichiro Nagasaka, ...2004 Volume 73 Issue 11 Pages 3166-3170
Published: November 15, 2004
Released on J-STAGE: July 25, 2007
JOURNAL RESTRICTED ACCESSThe temperature dependence of the absorption spectra of 2,2′-bithiophene and 2,2′:5′,2′′-terthiophene isolated molecules in cyclodextrin (CyD) were investigated between 15 K to room temperature (RT). The optical absorption spectra of BT molecules in β- and γ-CyD, (BT)β-CyD and (BT)γ-CyD are nearly the same between 15 K and RT. Those of TT are almost the same for (TT)β-CyD and (TT)γ-CyD. Anomalous temperature dependence of the absorption intensities was observed. The absorption intensities of the isolated molecules of BT and TT in CyD, (BT)CyD and (TT)CyD increase with increasing temperatures. The s-trans states of (BT)CyD and (TT)CyD convert to the s-cis states at high temperatures through the rotational vibration around the single bond between thiophene rings. The allowed transition of the s-cis conformation would mix to the forbidden transition of s-trans conformation, thus the absorption intensity increases at high temperatures.View full abstractDownload PDF (249K) -
Yunori Nisikawa, Manabu Usuda, Jun-ichi Igarashi2004 Volume 73 Issue 11 Pages 3171-3176
Published: November 15, 2004
Released on J-STAGE: July 25, 2007
JOURNAL RESTRICTED ACCESSWe investigate theoretically the resonant inelastic X-ray scattering (RIXS) at the K edge of Si on the basis of an ab initio calculation. We calculate the RIXS spectra with systematically varying transfered-momenta, incident-photon energy and incident-photon polarization. We confirm the anisotropy of the experimental spectra by Y. Ma et al. [Phys. Rev. Lett. 74 (1995) 478], providing a quantitative explanation of the spectra.View full abstractDownload PDF (249K) -
D. N. Thao, S. Katayama, K. Tomizawa2004 Volume 73 Issue 11 Pages 3177-3181
Published: November 15, 2004
Released on J-STAGE: July 25, 2007
JOURNAL RESTRICTED ACCESSA numerical simulation of terahertz (THz) radiation by coherent longitudinal optical (LO) phonons in GaAs p–i–n diodes under high electric fields is presented, with emphasis on the important role of a velocity overshoot of free carriers in coherent phonon generation. The dynamics of non-equilibrium photoexcited carriers is simulated by adopting a self-consistent ensemble Monte Carlo method. The explicit comparison of THz signals between calculations and experiments is carried out by taking into account the electronic and ionic accelerations. It is shown that the coherent phonon oscillations emitting the THz radiation are excited resonantly by synchronization between the proper lattice oscillation and ultrafast transients of electronic polarization within the initial period of lattice vibration. The appearance of saturation in THz amplitude due to the coherent phonon above 150 kV/cm as well as a significant phase shift of the oscillatory THz signal is predicted.View full abstractDownload PDF (647K) -
H. Yamaoka, M. Oura, M. Taguchi, T. Morikawa, K. Takahiro, A. Terai, K ...2004 Volume 73 Issue 11 Pages 3182-3191
Published: November 15, 2004
Released on J-STAGE: July 25, 2007
JOURNAL RESTRICTED ACCESSThe measurements combining Kβ resonant x-ray emission and partial fluorescence yield spectroscopy were performed for Fe metal, Fe2O3 and Fe3O4 near K absorption edge. Spin states of these materials are studied systematically with considering the origins of the Kβ′ line and of the pre-edge peak. Theoretical calculations for the cluster model of Fe2O3 were performed and reproduce well the experimental emission spectra. Resonant Raman scattering effect both in the absorption edge and in the pre-edge regions was observed and compared with the theory. Chemical effects between metal and its oxides were also discussed.View full abstractDownload PDF (580K) -
H. T. Jeong, E. Fleury, W. T. Kim, D. H. Kim, K. Hono2004 Volume 73 Issue 11 Pages 3192-3197
Published: November 15, 2004
Released on J-STAGE: July 25, 2007
JOURNAL RESTRICTED ACCESSIn order to investigate the mechanical relaxation behavior of the Zr36Ti24Be40 amorphous alloy, the dynamic mechanical properties were measured using dynamic mechanical analyzer (DMA). From the data collected during isothermal multi-frequency dynamic mechanical measurements, the master curves for storage and loss moduli over a broad range of temperature were constructed using the time–temperature superposition (TTS) principle. The temperature dependence of the shift factor was found to follow the Arrhenius relationship and the activation energies, calculated from the Arrhenius relationship, were about 93 and 390 kJ/mol for low temperature mechanical relaxation and viscous flow, respectively. According to the temperature dependence of the shift factor above Tg, no evidence for phase separation was found. The fragility index was also calculated from the relationship between shift factors and temperature and was found to be m≈34, suggesting that the Zr36Ti24Be40 amorphous alloy can be classified into the ‘strong’ glass.View full abstractDownload PDF (240K) -
Katsumasa Kamiya, Kenji Shiraishi, Atsushi Oshiyama2004 Volume 73 Issue 11 Pages 3198-3208
Published: November 15, 2004
Released on J-STAGE: July 25, 2007
JOURNAL RESTRICTED ACCESSWe report total-energy electronic-structure calculations based on the density functional theory performed for two important proteins, polyglycine with infinite length and cytochrome c oxidase. We have found that the both proteins are semiconductors with the high-lying occupied states and the low-lying unoccupied states having the characters of the non-bonding of O and the antibonding π of O, C, N orbitals, respectively. We have also found a peculiar electron state that has a free-electron-like spacial distribution in the internal space of the proteins (Nearly Free Electron state). It is found that the exchange–correlation potential as well as the electrostatic environment caused by hydrogen renders the Nearly Free Electron state appearing near the Fermi-level (or the fundamental energy gap), suggesting its possible important role in electronic processes in the proteins. We have also found that the spacial distribution of the lowest unoccupied state of cytochrome c oxidase is different between the oxidized and the reduced forms. Relations between atomic and electronic structures in cytochrome c oxidase are clarified.View full abstractDownload PDF (579K) -
M. Ebrahim Fouladvand, M. Reza Shaebani, Zeinab Sadjadi2004 Volume 73 Issue 11 Pages 3209-3214
Published: November 15, 2004
Released on J-STAGE: July 25, 2007
JOURNAL RESTRICTED ACCESSWe propose a two dimensional probabilistic cellular automata for the description of traffic flow in a small city network composed of two intersections. The traffic in the network is controlled by a set of traffic lights which can be operated both in fixed-time and a traffic responsive manner. Vehicular dynamics is simulated and the total delay experienced by the traffic is evaluated within specified time intervals. We investigate both decentralized and centralized traffic responsive schemes and in particular discuss the implementation of the green-wave strategy. Our investigations prove that the network delay strongly depends on the signalisation strategy. We show that in some traffic conditions, the application of the green-wave scheme may destructively lead to the increment of the global delay.View full abstractDownload PDF (336K)