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Volume 75, Issue 3
Displaying 1-44 of 44 articles from this issue
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Kiyoshi Ueda2006 Volume 75 Issue 3 Pages 032001
Published: March 15, 2006
Released on J-STAGE: August 27, 2009
JOURNAL RESTRICTED ACCESSThis article provides a review of the current status of core excitation and de-excitation spectroscopy studies of free atoms and molecules using a high-resolution soft X-ray monochromator and a high-resolution electron energy analyzer, installed in the soft X-ray photochemistry beam line at SPring-8. Experimental results are discussed for 1s excitation of Ne, O 1s excitation of CO and H2O, and F 1s excitation of CF4.View full abstractDownload PDF (1248K) -
Hideo Hasegawa2006 Volume 75 Issue 3 Pages 033001
Published: March 15, 2006
Released on J-STAGE: August 27, 2009
JOURNAL RESTRICTED ACCESSFinite N-unit Langevin models with additive and multiplicative noises have been studied with the use of the augmented moment method (AMM) previously proposed by the author [H. Hasegawa: Phys. Rev. E 67 (2003) 041903]. Original N-dimensional stochastic equations are transformed into the three-dimensional deterministic equations for means and fluctuations of local and global variables. Calculated results of our AMM are in good agreement with those of direct simulation (DS). We have shown that although the effective strength of the additive noise of the N-unit system is scaled as β(N)=β(1)⁄\\sqrtN, it is not the case for multiplicative noise [α(N)≠α(1)⁄\\sqrtN], where α(N) and β(N) denote the strengths of multiplicative and additive noises, respectively, for the size-N system. It has been pointed out that the naive assumption of α(N)=α(1)⁄\\sqrtN leads to a result that violates the central-limit theorem and that does not agree with those of DS and AMM.View full abstractDownload PDF (95K) -
Kazuya Saito, Masakazu Amano, Yasuhisa Yamamura, Takeo Tojo, Tooru Ata ...2006 Volume 75 Issue 3 Pages 033601
Published: March 15, 2006
Released on J-STAGE: August 27, 2009
JOURNAL RESTRICTED ACCESSThe heat capacity of a ferroelectrics consisting of two organic components having a centrosymmetric molecular shape, phenazine–chloranilic acid, was precisely measured by adiabatic calorimetry below room temperature. The paraelectric–ferroelectric phase transition was detected at 248 K as a heat capacity anomaly. The excess entropy involved is consistent with the previously assumed displacive nature. In addition to the ferroelectric phase transition, two phase transitions were observed in heat capacity and dielectric constant at 136 and 146 K.View full abstractDownload PDF (177K) -
Keisuke Shigetoh, Tetsuya Sasakawa, Kazunori Umeo, Toshiro Takabatake2006 Volume 75 Issue 3 Pages 033701
Published: March 15, 2006
Released on J-STAGE: August 27, 2009
JOURNAL RESTRICTED ACCESSWe report on the measurements of magnetic susceptibility χ, electrical resistivity ρ, specific heat C, and thermopower S of Ce4Ni3Pb4. This compound crystallizes in the trigonal (R3) La4Ni3Pb4-type structure, in which Ce atoms occupy two inequivalent sites. Both C(T) and ρ(T) show anomalies at TM=4 K and TN=3 K, respectively. On the other hand, M⁄B=χ(T) shows no anormaly at TM, but exhibits a considerable increase below TN. At 2 K, a hysteresis loop of magnetization has a small spontaneous moment, 2×10−3 μB/Ce. With increasing magnetic field, the ferromagnetic behavior in χ(T) is suppressed and instead, a characteristic peak of an antiferromagnetic transition appears at B=1 T. The weak ferromagnetism can be ascribed to the Dzyaloshinsky–Moriya interaction which may be present in Ce4Ni3Pb4 without inversion symmetry. An extrapolation of the plot of C⁄T vs T2 below 1 K yields γ=200 mJ/(Ce mol K2). Thus, this compound is a rare example of a Ce-based compound in which a heavy-fermion state survives in the weak ferromagnetic state.View full abstractDownload PDF (393K) -
Masashi Fujisawa, Toshio Ono, Hideyasu Fujiwara, Hidekazu Tanaka, Vadi ...2006 Volume 75 Issue 3 Pages 033702
Published: March 15, 2006
Released on J-STAGE: August 27, 2009
JOURNAL RESTRICTED ACCESSTlCuCl3 is a coupled spin dimer system, which has a singlet ground state with an excitation gap of Δ⁄gμB=5.5 T. TlCu1−xMgxCl3 doped with nonmagnetic Mg2+ ions undergoes impurity-induced magnetic ordering. Because triplet excitation with a finite gap still remains, this doped system can also undergo magnetic-field-induced magnetic ordering. Through specific heat measurements and neutron scattering experiments under a magnetic field, we investigated the phase diagram in TlCu1−xMgxCl3 with x∼0.01, and found that impurity- and field-induced ordered phases are the same. The gapped spin liquid state observed in pure TlCuCl3 is completely wiped out by the small amount of doping.View full abstractDownload PDF (143K) -
N. Hanasaki, M. Matsuda, H. Tajima, E. Ohmichi, T. Osada, T. Naito, T. ...2006 Volume 75 Issue 3 Pages 033703
Published: March 15, 2006
Released on J-STAGE: August 27, 2009
JOURNAL RESTRICTED ACCESSMaterials containing Fe(Pc)(CN)2 dicyano(phthalocyaninato)iron molecules show a giant negative magnetoresistance from the interaction between the conduction and the local moment. Under a magnetic field, the resistance becomes two orders of magnitude smaller than the zero-field resistance. The magnetic-field-angle dependence of the magnetoresistance reflects the symmetry of the Fe(Pc)(CN)2 molecule. We discuss, according to the scaling relation, the correlation between the magnetoresistance and the molecular spin fluctuation.View full abstractDownload PDF (689K) -
Kazumasa Miyake, Hiroaki Ikeda2006 Volume 75 Issue 3 Pages 033704
Published: March 15, 2006
Released on J-STAGE: August 27, 2009
JOURNAL RESTRICTED ACCESSThe true meaning of the terms “localized” and “itinerant”, frequently used in the interpretations of de Haas–van Alphen (dHvA) experiments of Ce-based heavy fermion metals, is argued. If the magnetic field H used in a dHvA measurement is larger than the threshold value of the order of the hybridization gap, the majority band of the quasiparticles would be filled up, and the Fermi surface (FS) would shift to the surface on which the conduction electrons have the Fermi energy without H. Then, the total number of electrons wrapped by the FS appears to decrease by one (f) electron per unit cell of the lattice. This phenomenon has been regarded as the “localization” of f-electrons, although f-electrons are never localized. As explicit examples, the transformation of the FS in CeRhIn5 and CeIn3 under pressure and that in CeRu2Si2 near a pseudo-metamagnetic transition are discussed.View full abstractDownload PDF (126K) -
Keiji Yada, Hiroshi Kontani2006 Volume 75 Issue 3 Pages 033705
Published: March 15, 2006
Released on J-STAGE: August 27, 2009
JOURNAL RESTRICTED ACCESSTo study the possible mechanism of superconductivity in Na0.35CoO2, we examine the interaction between all the relevant optical phonons (breathing and shear phonons) and t2g (a1g+eg′) electrons of Co ions, and study the transition temperature for s-wave superconductivity. The obtained Tc is very low when the eg′ valence bands are far below the Fermi level. However, Tc is strongly enhanced when the top of the eg′ valence bands is close to the Fermi level (e.g., −50 meV), thanks to the interband hopping of Cooper pairs caused by shear phonons. This “valence-band Suhl–Kondo mechanism” due to shear phonons is important in understanding the superconductivity in Na0.35CoO2. By the same mechanism, the kink structure of the band dispersion observed by angle-resolved photoemission spectroscopy (ARPES) measurements, which indicates the strong mass enhancement (m*⁄m∼3) due to optical phonons, is also explained.View full abstractDownload PDF (128K) -
Yoshiki Imai, Keitaro Sakurazawa, Tetsuro Saso2006 Volume 75 Issue 3 Pages 033706
Published: March 15, 2006
Released on J-STAGE: August 27, 2009
JOURNAL RESTRICTED ACCESSAnomalous metal–insulator transition observed in filled skutterudite CeOs4Sb12 is investigated by constructing the effective tight-binding model with the Coulomb repulsion between f electrons. By using the mean field approximation, magnetic susceptibilities are calculated and the phase diagram is obtained. When the band structure has a semimetallic character with small electron and hole pockets at Γ and H points, a spin density wave transition with an ordering vector Q=(1,0,0) occurs due to the nesting property of the Fermi surfaces. Magnetic field enhances this phase in accord with the experiments.View full abstractDownload PDF (178K) -
Hiroya Nakao2006 Volume 75 Issue 3 Pages 034001
Published: March 15, 2006
Released on J-STAGE: August 27, 2009
JOURNAL RESTRICTED ACCESSA system of globally coupled phase oscillators subject to an external input is considered as a simple model of neural circuits coding external stimulus. The information coding efficiency of the system in its asynchronous state is quantified using Fisher information. The effect of coupling and noise on the information coding efficiency in the stationary state is analyzed. The relaxation process of the system after the presentation of an external input is also studied. It is found that the information coding efficiency exhibits a large transient increase before the system relaxes to the final stationary state.View full abstractDownload PDF (353K) -
S. Tadaki, M. Kikuchi, A. Nakayama, K. Nishinari, A. Shibata, Y. Sugiy ...2006 Volume 75 Issue 3 Pages 034002
Published: March 15, 2006
Released on J-STAGE: August 27, 2009
JOURNAL RESTRICTED ACCESSThe temporal behavior of expressway traffic flow is a complex mixture of various time scales. The fundamental response time of drivers is on the order of 1 s, and the periodic appearances of traffic congestion reflect our social activities. We need some filters to extract proper dynamical fluctuations from raw observed traffic data. We employ the detrended fluctuation analysis (DFA) for studying long-range correlation in the time sequence of traffic flow. The time series of expressway traffic flow is understood to consist of periodic trends with power-law fluctuation. The power spectrum P(k) behaves as P(k)∼k−β with β∼1. The power-law fluctuation is observed in the wide time range from minutes to months.View full abstractDownload PDF (201K) -
Yosuke Yoshimura2006 Volume 75 Issue 3 Pages 034003
Published: March 15, 2006
Released on J-STAGE: August 27, 2009
JOURNAL RESTRICTED ACCESSThe solvent effect in a mixed solvent on the thermodynamical properties of a solute molecule is studied with a simplified model system. The solvent molecules in the model system are distinguished only by the interaction with the solute molecule, which is assumed as a square-well interaction. The exact relationship between the thermodynamical quantities in the single-component solvent and those in the mixed solvent are derived through the bond-number (BN) distribution of the solute molecule; the bond number is the number of interacting molecules in the potential well of the solute molecule. The BN distributions are evaluated for the hard-sphere fluid using the Monte Carlo method over a wide density region. The mean field approximation does not work well at low mole fraction of the interacting component in the mixed solvent due to the fluctuation of the local composition. The effect of the fluctuation of the local composition was reproduced by the modified independent-site model under the mean field approximation, in which the fluctuation of the composition is assumed to take place independently at hypothetical sites around a solute molecule.View full abstractDownload PDF (238K) -
Hidetoshi Nishimori, Masayuki Ohzeki2006 Volume 75 Issue 3 Pages 034004
Published: March 15, 2006
Released on J-STAGE: August 27, 2009
JOURNAL RESTRICTED ACCESSA conjecture is given for the exact location of the multicritical point in the phase diagram of the ±J Ising model on the triangular lattice. The result pc=0.8358058 agrees well with a recent numerical estimate. From this value, it is possible to derive a comparable conjecture for the exact location of the multicritical point for the hexagonal lattice, pc=0.9327041, again in excellent agreement with a numerical study. The method is a variant of duality transformation to relate the triangular lattice directly with its dual triangular lattice without recourse to the hexagonal lattice, in conjunction with the replica method.View full abstractDownload PDF (93K) -
Tomokazu Honda, Haruo Honjo, Hiroaki Katsuragi2006 Volume 75 Issue 3 Pages 034005
Published: March 15, 2006
Released on J-STAGE: August 27, 2009
JOURNAL RESTRICTED ACCESSWe report experimental results of anisotropic viscous fingering in a large scale Hele–Shaw cell. This fluid dynamical system corresponds to crystal growth system very well, and we can observe faceted growth, surface tension dendrite, tip oscillating growth, tip splitting growth and kinetic dendrite increasing the injected gas pressure. The results of surface tension dendrite and kinetic dendrite quantitatively agree with the theoretical results. Tip oscillating growth and tip splitting growth are observed between the morphological transitions, which we discuss with the ratio of the area to the contour of the morphology.View full abstractDownload PDF (2037K) -
Kazushige Maeda, Sachiko Ito, Hideaki Itoh, Osamu Konno, Hideto Matsuy ...2006 Volume 75 Issue 3 Pages 034201
Published: March 15, 2006
Released on J-STAGE: August 27, 2009
JOURNAL RESTRICTED ACCESSThe photoneutron cross section for 13C was measured in the tagged photon energy range Eγ=17–70 MeV. Substantial forward to backward asymmetry was observed above the giant dipole resonance region. The observed asymmetries were analyzed by the direct and semi-direct model, assuming two isovector E2 resonances, which locate at Ex=30.9±1.5 MeV with Γ=8±6 MeV and Ex=43.2±1.8 MeV with Γ=13±6 MeV. They are identified as the T< and T> isospin components of the isovector quadrupole strengths, which exhaust most of the sum rule.View full abstractDownload PDF (281K) -
Mustafa Kemal Öztürk, Süleyman Özçelik2006 Volume 75 Issue 3 Pages 034301
Published: March 15, 2006
Released on J-STAGE: August 27, 2009
JOURNAL RESTRICTED ACCESSThe calculation of the elastic scattering properties of mixtures composed of ultracold Rb–K atoms is reported and compared with experimental results in detail. The improved potentials for both the singlet and triplet molecular states of Rb–K are presented, and the scattering lengths at and the effective range re are calculated with numeric and semiclassical methods for Rb–K in the triplet and singlet state. In addition, the convergence of these scattering properties depending on a K0 parameter is investigated using quantum defect theory. Other results of the evaporative cooling that include the cross section and the spin–charge cross section, the rate coefficient as a function of the energy and ultralow temperature are also presented in this study.View full abstractDownload PDF (267K) -
Masabumi Miyabe, Christopher Geppert, Masaaki Kato, Masaki Oba, Ikuo W ...2006 Volume 75 Issue 3 Pages 034302
Published: March 15, 2006
Released on J-STAGE: August 27, 2009
JOURNAL RESTRICTED ACCESSHigh-resolution resonance ionization spectroscopy has been utilized to determine a precise ionization potential of Ca. Three-step resonance excitation with single-mode extended-cavity diode lasers populates long and unperturbed Rydberg series of 4snp (1P1) and 4snf (1F3) states in the range of n=20–150. Using an extended Ritz formula for quantum defects, the series convergence limit has been determined to be 49305.9240(20) cm−1 with the accuracy improved one order of magnitude higher than previously reported ones.View full abstractDownload PDF (445K) -
Yuki Kato, Kaoru Fujimura2006 Volume 75 Issue 3 Pages 034401
Published: March 15, 2006
Released on J-STAGE: August 27, 2009
JOURNAL RESTRICTED ACCESSSidewall effect on the Rayleigh–Bénard convection has been examined in a rectangular channel with finite aspect ratio, where the linear neutral stability curves avoid crossing on the Rayleigh number–aspect ratio plane. Numerical analysis shows that folded solution branches exist in the bifurcation diagram where the aspect ratio is adopted as the bifurcation parameter. To examine an origin of the fold, we formally derived amplitude equations. An analysis of the amplitude equations shows that certain nonlinear solutions, realized under the crossing of neutral stability curves, are split into two groups in the presence of the avoided crossing and that the folded branch arises.View full abstractDownload PDF (147K) -
Ying Guo, Guihua Zeng2006 Volume 75 Issue 3 Pages 034402
Published: March 15, 2006
Released on J-STAGE: August 27, 2009
JOURNAL RESTRICTED ACCESSTo construct a quantum code with much error-correcting ability, the philosophy of the quantum interleaving is illustrated by introducing the block interleaving techniques. Quantum interleaving is a process to rearrange the qubits of several states of the same code so as to spread the same quantum errors over multiple states. Utilizing the interleaving technique, the concatenated kn-qubit code is constructed in this paper with more error-correcting ability than utilizing only one n-qubit quantum error-correcting code (QECC) without introducing the redundant qubits. It hence suggests an important way to design an quantum convolution code as the classical convolutional code has been constructed. For the application, the proposed quantum interleaving technique becomes an effective means to combat quantum bursts of errors by converting quantum bursts of errors into quantum random errors.View full abstractDownload PDF (78K) -
Sanae-I. Itoh, Kimitaka Itoh, Hazime Mori2006 Volume 75 Issue 3 Pages 034501
Published: March 15, 2006
Released on J-STAGE: August 27, 2009
JOURNAL RESTRICTED ACCESSA statistical model for plasma turbulence is examined by employing a basis from the Mori method [H. Mori: Prog. Theor. Phys. 33 (1965) 423]. The Mori method provides a base for the existence of the separation of the memory function from fluctuating force in the nonlinear dynamical equations. An analytic model for the turbulent damping coefficient is derived by use of the Green’s function. The model formula takes a non-Markovian form, representing the property of the time-reversibility of the basic equation. A recurrence formula is derived. The continued fraction form is also derived. A formula of the eddy-damping rate is derived. A rigorous relation which is derived by the Mori method is discussed, and is compared to the modelling. This comparison explains a nature of approximation in the modelling.View full abstractDownload PDF (152K) -
Kazuhiro Fuchizaki2006 Volume 75 Issue 3 Pages 034601
Published: March 15, 2006
Released on J-STAGE: August 27, 2009
JOURNAL RESTRICTED ACCESSThe expression known as Murnaghan’s equation of state in high-pressure research community is mathematically a correct solution to the equation of bulk modulus but is valid only within a very limited parameter space. Moreover, the equation of state in question exhibits a peculiar behavior at high pressures when fitted to compression data. An alternative expression with a much wider range of validity is given. No peculiarity appears in the resultant compression curve. The latter expression thus provides a new tool as an infinitesimal-strain equation of state for quick estimate of compression characteristics of substances.View full abstractDownload PDF (109K) -
Hisao Kobayashi, Yoshitaka Yoda, Makoto Shirakawa, Akira Ochiai2006 Volume 75 Issue 3 Pages 034602
Published: March 15, 2006
Released on J-STAGE: August 27, 2009
JOURNAL RESTRICTED ACCESS151Eu nuclear resonant inelastic scattering (NRIS) experiments have been performed on the charge ordering Eu4As3 compound from 301 to 406 K and the Eu partial phonon densities of states were extracted from the observed spectra. We derived the thermodynamic parameters from inelastic components in the observed NRIS spectra using the sum rules. The mean recoilless fraction shows the softening in the lattice vibration of the Eu ion around the charge ordering temperature in spite of no anomaly in the temperature dependence of average sound velocity. We present by the temperature dependence of mean force constant that the hybridization between the 4f states and the conduction or valence bands in Eu4As3 plays a role around the charge ordering temperature and in the valence fluctuating state.View full abstractDownload PDF (345K) -
Keiji Saito2006 Volume 75 Issue 3 Pages 034603
Published: March 15, 2006
Released on J-STAGE: August 27, 2009
JOURNAL RESTRICTED ACCESSThe characteristics of heat flow in a coupled magnetic system are studied. The coupled system is composed of a gapped chain and a gapless chain. The system size is assumed to be quite small so that the mean free path is comparable to it. When the parameter set of the temperatures of reservoirs is exchanged, the characteristics of heat flow are studied with the Keldysh Green function technique. The asymmetry of current is found in the presence of a local equilibrium process at the contact between the magnetic systems. The present setup is realistic and such an effect will be observed in real experiments. We also discuss the simple phenomenological explanation to obtain the asymmetry.View full abstractDownload PDF (117K) -
Akihiko Matsuyama2006 Volume 75 Issue 3 Pages 034604
Published: March 15, 2006
Released on J-STAGE: August 27, 2009
JOURNAL RESTRICTED ACCESSA mean field model is introduced to describe phase separations and crystalline ordering in colloidal solutions. We introduce translational order parameters for crystalline ordering of cubic crystals. Combining a modified-Flory–Huggins theory for colloidal solutions with a translational order parameter of a face-centered-cubic structure for colloidal crystals, we derive a free energy, which is given by one conserved order parameter (concentration) and one nonconserved order parameter (translational order parameter of colloids). We calculate the phase diagrams of colloidal solutions on the temperature–concentration plane and find a metastable liquid–liquid, liquid–solid, solid–solid phase separation, and triple point, which can be defined by the translational order parameter and concentration. Depending on the size of a colloid and the strength of an attractive interaction between colloids, the theory presented successfully describes the features of the phase diagrams observed in a wide variety of colloidal systems. We also compare our theory with the experimental phase diagram of lens protein solutions.View full abstractDownload PDF (251K) -
Koji Kaneko, Naoto Metoki, Tatsuma D. Matsuda, Masahumi Kohgi2006 Volume 75 Issue 3 Pages 034701
Published: March 15, 2006
Released on J-STAGE: August 27, 2009
JOURNAL RESTRICTED ACCESSNeutron powder diffraction experiments were carried out on the heavy-fermion superconductor PrOs4Sb12 down to 7.7 K in order to reveal the thermal displacement of Pr and investigate the possible existence of off-center potential minima for Pr in the Sb cage. Rietveld analysis with the structure in which Pr is located at the center of the Sb cage well reproduces the observed patterns. A large thermal displacement was obtained for Pr of UPr=0.0344 Å2 at 295.1 K, roughly corresponding to a mean thermal displacement of 0.18 Å. This value is 5 times larger than those of other constituents, UOs and USb. UPr remains large, UPr=0.0062 Å2, even at 7.7 K, which is twice as large as UOs and USb. Neither structural transition nor significant change of the Sb cage accompanied this change in UPr. The large UPr and its strong temperature dependence indicate the rattling of Pr under a shallow potential in the Sb cage. An equal distribution of Pr at 12e sites (x00) was introduced to approximate the off-center potential minima. The R factors were not improved by the introduction of the off-center site.View full abstractDownload PDF (451K) -
H. Yamaoka, M. Taguchi, A. M. Vlaicu, H. Oohashi, K. Yokoi, D. Horiguc ...2006 Volume 75 Issue 3 Pages 034702
Published: March 15, 2006
Released on J-STAGE: August 27, 2009
JOURNAL RESTRICTED ACCESSBulk sensitive spectroscopies were performed for mixed valent compounds EuNi2(Si1−xGex)2 as a function of x, and Eu-sesquioxide (Eu2O3), using techniques of high-resolution partial-fluorescence yield (PFY) and resonant inelastic x-ray scattering (RIXS) at the Eu L3 absorption edge. The evolution of mean-valency as a function of chemical composition x in EuNi2(Si1−xGex)2 shows a drastic change between x=0.5 and 0.7. The experimental results also show a small amount of mixed valency for the end members, i.e., x=1 and 0 samples are also mixed valent. Single-impurity Anderson model calculations show good agreement with the PFY and RIXS experimental results, and thus provide a consistent set of electronic structure parameters. The composition controlled drastic change in mean-valence between x=0.5 and 0.7 is derived from a large hybridization change, consistent with the Kondo volume collapse picture.View full abstractDownload PDF (453K) -
Hideo Yoshioka2006 Volume 75 Issue 3 Pages 034703
Published: March 15, 2006
Released on J-STAGE: August 27, 2009
JOURNAL RESTRICTED ACCESSWe investigate Knight shift and nuclear spin relaxation rate in a charge-ordered state of the one-dimensional extended Hubbard model with a quarter-filled band by using RPA around the mean-field solution. It is shown that both quantities show splitting below the critical temperature of the charge order, as is experimentally observed. The relationships between the amount of the splitting in the both quantities and the charge disproportionation rate are discussed.View full abstractDownload PDF (259K) -
Hiori Kino, Tsuyoshi Miyazaki2006 Volume 75 Issue 3 Pages 034704
Published: March 15, 2006
Released on J-STAGE: August 27, 2009
JOURNAL RESTRICTED ACCESSWithin the framework of the density functional theory, we calculate the electronic structure of α-(BEDT-TTF)2I3 at 8 K and room temperature at ambient pressure and with uniaxial strain along the a- and b-axes. We confirm the existence of anisotropic Dirac cone dispersion near the chemical potential. We also extract the orthogonal tight-binding parameters to analyze physical properties. An investigation of the electronic structure near the chemical potential clarifies that effects of uniaxial strain along the a-axis is different from that along the b-axis. The carrier densities show T2 dependence at low temperatures, which may explain the experimental findings not only qualitatively but also quantitatively.View full abstractDownload PDF (630K) -
Shutaro Chiba, Yuta Baba, Yoshiyuki Ono2006 Volume 75 Issue 3 Pages 034705
Published: March 15, 2006
Released on J-STAGE: August 27, 2009
JOURNAL RESTRICTED ACCESSThe effects of electron–electron (e–e) interactions on the two-dimensional (2D) Peierls state are discussed using the 2D Peierls–Hubbard model (2D PHM) in the limit of U>>t0, where U is the on-site e–e interaction parameter between up and down spin electrons and t0 is the electron transfer integral between nearest neighbor sites. In this limit, the 2D PHM can be mapped onto the 2D spin-Peierls model (2D SPM) in which the effect of the lattice distortion is taken into account in the spin exchange interaction of the 2D Heisenberg model. As was demonstrated in a previous paper [J. Phys. Soc. Jpn. 69 (2000) 1769], the ground state of the 2D electron–lattice (e–l) system (the 2D 1/2-filled SSH model) is the so-called multimode Peierls state where the lattice distortion involves Fourier components with the nesting wave vector Q=(π⁄a,π⁄a), a being the lattice constant, and with those paralell to it. Using the exact diagonalization technique it is shown that the spin-Peierls transition with a mutlimode lattice distortion can occur in the 2D spin–lattice system similarly as in the 2D e–l system.View full abstractDownload PDF (235K) -
Tsuguhito Nakano, Kazuhiko Kuroki2006 Volume 75 Issue 3 Pages 034706
Published: March 15, 2006
Released on J-STAGE: August 27, 2009
JOURNAL RESTRICTED ACCESSWe study the pressure dependence of the superconducting transition temperature of an organic superconductor β′-(BEDT-TTF)2ICl2 by applying the fluctuation exchange method to the Hubbard model on the original two-band lattice at 3/4 filling rather than the single-band model in the strong dimerization limit. Our study is motivated by the fact that hopping parameters evaluated from a first-principles study suggest that the dimerization of the BEDT-TTF molecules is not very strong particularly high pressures. Solving the linearized Eliashberg’s equation, a dxy-wavelike superconducting state with realistic values of Tc is obtained in a pressure regime somewhat higher than the actual experimental result. These results are similar to those obtained within the single-band model in the previous study by Kino et al. We conclude that the resemblance to the dimer limit is due to a combination of a good Fermi surface nesting, a large density of states near the Fermi level, and a moderate dimerization, which cooperatively enhance electron correlation effects and also the superconducting Tc.View full abstractDownload PDF (469K) -
Yoichi Nishiwaki, Tetsuya Kato, Yasuaki Oohara, Akira Oosawa, Norikazu ...2006 Volume 75 Issue 3 Pages 034707
Published: March 15, 2006
Released on J-STAGE: August 27, 2009
JOURNAL RESTRICTED ACCESSA powder and single-crystal neutron diffraction study was performed on the structural and magnetic phase transitions of the distorted-triangular-lattice Ising-like antiferromagnet TlCoCl3. From the results of powder sample measurement, the crystal structures were identified as the P63cm and Pbca structures at the intermediate-temperature (75<T<165 K) and lowest-temperature (T<68 K) phases, respectively. From the results of single-crystal measurement, it was clarified that Ising spins were arranged in an up-up-down-down manner with a triple-domain formation below the Néel temperature. Satellite peaks on the shoulder of magnetic peaks were observed near the Néel temperature.View full abstractDownload PDF (867K) -
M. Mori, T. Tohyama, S. Maekawa2006 Volume 75 Issue 3 Pages 034708
Published: March 15, 2006
Released on J-STAGE: August 27, 2009
JOURNAL RESTRICTED ACCESSWe study doping dependence of interlayer hoppings, t⊥, in multilayered cuprates with four or more CuO2 planes in a unit cell. When the double occupancy is forbidden in the plane, an effective amplitude of t⊥ in the Gutzwiller approximation is shown to be proportional to the square root of the product of doping rates in adjacent two planes, i.e., teff⊥∝t⊥\\sqrtδ1δ2, where δ1 and δ2 represent the doping rates of the two planes. More than three-layered cuprates have two kinds of CuO2 planes, i.e., inner- and outer planes (IP and OP), resulting in two different values of teff⊥, i.e., teff⊥1∝t⊥\\sqrtδIPδIP between IP’s, and teff⊥2∝t⊥\\sqrtδIPδOP between IP and OP. Fermi surfaces are calculated in the four-layered t–t′–t″–J model by the mean-field theory. The order parameters, the renormalization factor of t⊥, and the site-potential making the charge imbalance between IP and OP are self-consistently determined for several doping rates. We show the interlayer splitting of the Fermi surfaces, which may be observed in the angle resolved photoemission spectroscopy measurement.View full abstractDownload PDF (371K) -
Annamária Kiss, Yoshio Kuramoto2006 Volume 75 Issue 3 Pages 034709
Published: March 15, 2006
Released on J-STAGE: August 27, 2009
JOURNAL RESTRICTED ACCESSCharacteristics of magnetic transitions in NpTGa5 with T=Co, Ni, Rh are explained in a unified way with use of a crystalline electric field (CEF) model of localized 5f4 electrons. The model takes a CEF doublet and a singlet as local states, and includes dipolar and quadrupolar intersite interactions in the mean-field theory. Diverse ordering phenomena are derived depending on the magnitude of interaction parameters, which qualitatively reproduce the experimentally observed magnetic behaviors in NpTGa5. The quadrupole degrees of freedom are essential to the diverse magnetic orders. It is argued that NpRhGa5 is close to a multicritical point where quadrupoles and dipoles with different directions are competing to order.View full abstractDownload PDF (176K) -
Satoru Maegawa, Yoshinori Sasaki2006 Volume 75 Issue 3 Pages 034710
Published: March 15, 2006
Released on J-STAGE: August 27, 2009
JOURNAL RESTRICTED ACCESSSpin dynamics in the antiferromagnetic ring Fe10 has been studied by means of magnetic susceptibility and 1H-NMR experiments. The spin–lattice relaxation rate 1⁄T1 above 40 K reflects the spin fluctuations in the continuous energy levels of the spin states, while the rate below 40 K indicates the development of antiferromagnetic correlations and discrete energy levels. Especially the experimental rates below 4 K can be expressed by an exponential function of the temperature with an energy gap between the singlet ground state and the triplet excited state. The field dependence of the low-lying energy levels was clearly revealed by the 1⁄T1 measurements. On the other hand, the spin–spin relaxation rate 1⁄T2 is dominated by the temperature-independent fluctuations of the nuclear dipolar fields and a small contribution proportional to 1⁄T1, and is consistent with the spectral widths.View full abstractDownload PDF (440K) -
Kazuhiko Ohmori, Machie Saitou, Guido Eilers, Masaaki Matsui2006 Volume 75 Issue 3 Pages 034711
Published: March 15, 2006
Released on J-STAGE: August 27, 2009
JOURNAL RESTRICTED ACCESSWe have prepared samples of the dilute magnetic semiconductor (CuIn)1−xMn2xS2 (x=0.0–0.3) and performed magnetic measurement. The magnetization curves were analyzed by considering two terms: the one was the contribution of the interactive Mn ions and the other one was the contribution of the isolated Mn ions. The decrease in the second contribution with the increase in Mn concentration was attributed to the decrease in the number of the isolated Mn ions and the increase in the number of Mn ion clusters such as pairs, triangles and networks. The dependences of the inverse magnetic susceptibilities on the temperature were measured and investigated using the above two terms. The observed data were ferrimagnetic like and the introduced formula for the dependences of the data on the temperature also showed the same tendency.View full abstractDownload PDF (178K) -
Soshi Takeshita, Juichiro Arai, Tatsuo Goko, Kusuo Nishiyama, Kanetada ...2006 Volume 75 Issue 3 Pages 034712
Published: March 15, 2006
Released on J-STAGE: August 27, 2009
JOURNAL RESTRICTED ACCESSA muon spin relaxation (μSR) experiment has been performed in zero-field (ZF) and longitudinal-field (LF) conditions for a Ca3Co2O6 sample which has an antiferromagnetic triangular lattice on the ab-plane with Ising ferromagnetic chains along the c-axis. At 150 K, far above the magnetic transition temperature Tc1 (=25 K) determined from magnetization data, exponential-like relaxation curves are observed in ZF-μSR time spectra, suggesting the development of intrachain ferromagnetic coupling even far above Tc1. Below the temperature Tc2 (∼12 K) where magnetization is saturated, the tail of the relaxation curve reaches 1/3 the value of the amplitude in ZF-μSR spectra and the decoupling phenomenon in LF-μSR, that is, a further rise of the tail due to the applied LF, can be observed, implying the appearance of the static internal magnetic field. However, between Tc1 and Tc2, the above-mentioned phenomenon cannot be observed. This indicates that the internal magnetic field at each muon site is not static but rather dynamical with the fluctuation time τc (∼21 ns) although the magnetization gives large values between these temperatures. This fact must indicate the presence of a partially disordered antiferromagnetic state peculiar to the frustrated magnetic system.View full abstractDownload PDF (228K) -
T. Tohyama2006 Volume 75 Issue 3 Pages 034713
Published: March 15, 2006
Released on J-STAGE: August 27, 2009
JOURNAL RESTRICTED ACCESSSymmetry of photoexcited states with two photoinduced carriers in two-dimensional Mott insulators is examined by applying the numerically exact diagonalization method to finite-size clusters of a half-filled Hubbard model in the strong-coupling limit. The symmetry of minimum-energy bound state is found to be s-wave, which is different from a dx2−y2 wave of a two-hole pair in doped Mott insulators. We demonstrate that the difference is originated from an exchange of fermions due to the motion of a doubly occupied site. Correspondingly large-shift Raman scattering across the Mott gap exhibits a minimum-energy excitation in the A1 (s-wave) channel. We discuss implications of the results for the Raman scattering and other optical experiments.View full abstractDownload PDF (494K) -
Tetsuya Takimoto2006 Volume 75 Issue 3 Pages 034714
Published: March 15, 2006
Released on J-STAGE: August 27, 2009
JOURNAL RESTRICTED ACCESSA theory of metal–insulator transition in PrRu4P12 is developed from a microscopic point of view, based on j–j coupling scheme. For the metal–insulator transition, we propose antiferro-hexadecapole order without breaking local symmetry. It is shown that the hexadecapole ordered state appears in the case that the ground state of Pr-ion is Γ1 singlet, and conduction electrons dominantly belong to Γ5 in Th point group. For half-filled conduction band, system becomes insulator in the ordered state due to gap formed by the antiferro-hexadecapole moment. The present scenario provides reasonable explanation for experimental results of PrRu4P12.View full abstractDownload PDF (147K) -
Shigeru Koikegami, Takashi Yanagisawa2006 Volume 75 Issue 3 Pages 034715
Published: March 15, 2006
Released on J-STAGE: August 27, 2009
JOURNAL RESTRICTED ACCESSWe investigate the superconductivity of a three-dimensional d–p model with a multilayer perovskite structure on the basis of the second-order perturabation theory within the weak coupling framework. Our model has been designed with multilayer high-Tc superconducting cuprates in mind. In our model, multiple Fermi surfaces appear, and the component of a superconducting gap function develops on each band. We have found that the multilayer structure can stabilize the superconductivity in a wide doping range.View full abstractDownload PDF (394K) -
H. Watanabe, Y. Mori, M. Yokoi, T. Moyoshi, M. Soda, Y. Yasui, Y. Koba ...2006 Volume 75 Issue 3 Pages 034716
Published: March 15, 2006
Released on J-STAGE: August 27, 2009
JOURNAL RESTRICTED ACCESSCo-oxides β-Na0.5CoO2 and γ-K0.5CoO2 have been prepared by the Na de-intercalation from α-NaCoO2 and by the floating-zone method, respectively. It has been found that successive phase transitions take place at temperatures Tc1 and Tc2 in both systems. The appearance of the internal magnetic field at Tc1 with decreasing temperature T indicates that the antiferromagnetic order exists at T≤Tc1, as in γ-Na0.5CoO2. For β-Na0.5CoO2, the transition temperatures and the NMR parameters determined from the data taken for magnetically ordered state are similar to those of γ-Na0.5CoO2, indicating that the difference of the stacking ways of the CoO2 layers between these systems do not significantly affect their physical properties. For γ-K0.5CoO2, the quantitative difference of the physical quantities are found from those of β- and γ-Na0.5CoO2. The difference between the values of Tci (i=1 and 2) of these systems might be explained by considering the distance between CoO2 layers.View full abstractDownload PDF (560K) -
T. Kaneko, H. Kudo, S. Tomita, R. Uchiyama2006 Volume 75 Issue 3 Pages 034717
Published: March 15, 2006
Released on J-STAGE: August 27, 2009
JOURNAL RESTRICTED ACCESSBased on the three-step model, we theoretically studied the energy distribution of low-energy (less than 50 eV) secondary electrons emitted from highly-oriented pyrolytic graphite (HOPG), induced by the 0.24 MeV/atom carbon-cluster Cn+ (n=1,2,4,8) ions. Here we treated the kinetic excitation process of an electron gas, described by the dynamical dielectric function. In the projectile system, we took into account the charge state, the spatial structure of the cluster and the size of the electron cloud on the constituent atoms. The numerical results show that the intensity of energy spectra per carbon ion is less than that induced by a single carbon ion at the equivalent speed. This sub-linear effect was supported by a recent experimental result. We concluded that this effect could be explained to a considerable extent by the screening effect and the vicinage effect of the incident cluster.View full abstractDownload PDF (170K) -
Thang Manh Hoang, Masahiro Nakagawa2006 Volume 75 Issue 3 Pages 034801
Published: March 15, 2006
Released on J-STAGE: August 27, 2009
JOURNAL RESTRICTED ACCESSPrevious research has shown that the chaos synchronization of multi-delay feedback systems with multi-delay driving signal has a high potential for application in secure communication due to its complexity in dynamics and in the driving signal. In this paper, a new encoding model for chaos-based secure communication is proposed by using the chaos synchronization of multi-delay feedback systems with multi-delay driving signal. Further, a new scheme of shift keying technique named the synchronization-manifold shift keying is devised and used in the secure communication system. Simulation results validate the new proposed encoding model.View full abstractDownload PDF (387K) -
Eiichi Yagi, Shigetoshi Koike, Takamasa Sugawara, Toetsu Shishido, Ter ...2006 Volume 75 Issue 3 Pages 034802
Published: March 15, 2006
Released on J-STAGE: August 27, 2009
JOURNAL RESTRICTED ACCESSThe site occupancy of hydrogen in 52 at. % Nb–48 at. % Mo alloys is investigated at room temperature for hydrogen concentrations 0.028 and 0.055 in the hydrogen–metal-atom ratio (CH=[H]⁄[M]) by the channelling method utilizing a nuclear reaction 1H(11B,α)αα with a 11B beam. A large portion of H atoms are located at sites displaced from tetrahedral (T) sites towards their nearest neighbour octahedral (O) sites by about 0.3 Å (displaced-T sites; d-T), which are similar to the sites observed in V under uniaxial stress and completely different from the sites observed in the Nb alloys containing undersized Mo atoms up to 26 at. %. For CH=0.028 and 0.055, 30–40% and 15–25% of H atoms are located at T sites, respectively.View full abstractDownload PDF (246K) -
Ishak Hashim, Wartono Sarma2006 Volume 75 Issue 3 Pages 035001
Published: March 15, 2006
Released on J-STAGE: August 27, 2009
JOURNAL RESTRICTED ACCESSDownload PDF (76K)
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