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- Proceedings of the Physico-Mathematical Society of Japan. 3rd Series
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- Tokyo Sugaku-Butsurigakukwai Kiji-Gaiyo
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Volume 73, Issue 8
Displaying 1-50 of 54 articles from this issue
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Wataru Kunishima, Akinobu Nishiyama, Hiroshi Tanaka, Tetsuji Tokihiro2004 Volume 73 Issue 8 Pages 2033-2036
Published: August 15, 2004
Released on J-STAGE: July 25, 2007
JOURNAL RESTRICTED ACCESSWe propose a method of constructing differential equations directly from cellular automata. Any elementary cellular automata (ECAs) introduced by Wolfram can be transformed into a partial differential equation (PDE) which preserves the time evolution patterns of the ECAs. In particular, some PDEs constructed by the method reproduce complex fractal and self-organizing patterns found in their corresponding ECAs. It is expected that the method can be extended for general cellular automata with more complex rules and/or in higher dimensions.View full abstractDownload PDF (244K) -
Atsushi Kawarada, Hisao Hayakawa2004 Volume 73 Issue 8 Pages 2037-2040
Published: August 15, 2004
Released on J-STAGE: July 25, 2007
JOURNAL RESTRICTED ACCESSThe simulation of granular particles in a quasi-two-dimensional container under vertical vibration as an experimental accessible model for granular gases is performed. The velocity distribution function obeys an exponential-like function during the vibration and deviates from the exponential function in free-cooling states. It is confirmed that this exponential-like distribution function is produced by Coulomb friction force. A Langevin equation with Coulomb friction is proposed to describe the motion of such a system.View full abstractDownload PDF (112K) -
Shin-ichi Kimura, Mitsuru Okuno, Hideaki Kitazawa, Fumihiko Ishiyama, ...2004 Volume 73 Issue 8 Pages 2041-2044
Published: August 15, 2004
Released on J-STAGE: July 25, 2007
JOURNAL RESTRICTED ACCESSThe temperature dependence of the electronic structure of CeBi arising from two types of antiferromagnetic transitions based on optical conductivity [σ(ω)] was observed. The σ(ω) spectrum continuously and discontinuously changes at 25 and 11 K, respectively. Between these temperatures, two peaks in the spectrum rapidly shift to the opposite energy sides as the temperature changes. Through a comparison with the band calculation as well as with the theoretical σ(ω) spectrum, this peak shift was explained by the energy shift of the Bi 6p band due to the mixing effect between the Ce 4f Γ8 and Bi 6p states. The single-layer antiferromagnetic (+−) transition from the paramagnetic state was concluded to be of the second order. The marked changes in the σ(ω) spectrum at 11 K, however, indicated the change in the electronic structure was due to a first-order-like magnetic transition from a single-layer to a double-layer (++−−) antiferromagnetic phase.View full abstractDownload PDF (256K) -
Hidekazu Okamura, Takahiro Michizawa, Takao Nanba, Takao Ebihara2004 Volume 73 Issue 8 Pages 2045-2048
Published: August 15, 2004
Released on J-STAGE: July 25, 2007
JOURNAL RESTRICTED ACCESSInfrared optical conductivity [σ(ω)] of the intermediate-valence compound YbAl3 has been measured at temperatures 8–690 K to study its microscopic electronic structures. Despite the highly metallic characteristics of YbAl3, σ(ω) exhibits a clear pseudogap (strong depletion of spectral weight) of about 60 meV below 40 K. It also shows a strong mid-infrared peak centered at ∼0.25 eV. The energy-dependent effective mass and scattering rate of the carriers obtained from the data indicate the formation of a heavy-mass Fermi liquid. These characteristic results are discussed in terms of the hybridization states between the Yb 4f and the conduction electrons. It is argued, in particular, that the pseudogap and the mid-infrared peak result from the indirect and direct gaps, respectively, within the hybridization state.View full abstractDownload PDF (257K) -
Mitsuaki Takigawa, Masanori Ichioka, Kazushige Machida2004 Volume 73 Issue 8 Pages 2049-2052
Published: August 15, 2004
Released on J-STAGE: July 25, 2007
JOURNAL RESTRICTED ACCESSThe field dependence of low-temperature thermal conductivity κ(H) observed on cuprates is explained by calculating κ(H) microscopically. The heat current carried by low-lying quasiparticles around a vortex core decreases with H due to its depletion by the H-induced moment centered at a core for an underdoped case. This leads to a common and consistent picture on an “anomalous core”. κ(H,T) is found to be a useful tool for probing quasiparticle structures in the mixed state in general.View full abstractDownload PDF (215K) -
Yasuhiro Tanaka, Youichi Yanase, Masao Ogata2004 Volume 73 Issue 8 Pages 2053-2056
Published: August 15, 2004
Released on J-STAGE: July 25, 2007
JOURNAL RESTRICTED ACCESSSuperconductivity close to charge ordering in quasi-two-dimensional 3⁄4-filled organic compounds is investigated for the θ-type structure. The effect of spin and charge fluctuations is calculated within random phase approximation for a relevant extended Hubbard model with both on-site (U) and intersite (V) Coulomb interactions on an anisotropic triangular lattice. It is found that both spin and charge fluctuations induce superconductivity with extended s-wave singlet pairing, which is similar to the dxy pairing state in the square lattice. In the vicinity of charge-density-wave instability, f-wave triplet pairing is also stable due to the effect of nearest-neighbor Coulomb interaction. The temperature dependences of superconductivity and charge-density-wave phase boundaries are also examined.View full abstractDownload PDF (114K) -
Hiromasa Yoshimura, Dai S. Hirashima2004 Volume 73 Issue 8 Pages 2057-2060
Published: August 15, 2004
Released on J-STAGE: July 25, 2007
JOURNAL RESTRICTED ACCESSThe superconducting order parameter in electron-doped high-temperature superconductors is calculated by fluctuation exchange approximation applied to a two-dimensional Hubbard model. In contrast to hole-doped cases, the so-called hot spots are located near the diagonals of the Brillouin zone in the electron-doped superconductors; this is found to result in the nonmonotonic angular dependence of the order parameter of dx2−y2 symmetry. This agrees with the implication obtained from electronic Raman scattering experiments, and the direct observation of this angular dependence is direct evidence of the superconductivity induced by antiferromagnetic spin fluctuations.View full abstractDownload PDF (205K) -
Satoshi Fujimoto2004 Volume 73 Issue 8 Pages 2061-2064
Published: August 15, 2004
Released on J-STAGE: July 25, 2007
JOURNAL RESTRICTED ACCESSWe analyze an asymptotically exact solution for the transition temperature of p-wave superconductivity near ferromagnetic criticality on the basis of three-dimensional electron systems in which scattering processes are dominated by exchange interactions with small momentum transfers. Taking into account all Feynman diagrams in the gap equation, we show that vertex corrections neglected in the conventional Eliashberg formalism enhance the dynamical retardation effect of the pairing interaction, and increase the superconducting transition temperature significantly, though they just give subleading corrections to properties of the normal state.View full abstractDownload PDF (127K) -
Eiji Ohmichi, Takahiko Masui, Sergey Lee, Setsuko Tajima, Toshihito Os ...2004 Volume 73 Issue 8 Pages 2065-2068
Published: August 15, 2004
Released on J-STAGE: July 25, 2007
JOURNAL RESTRICTED ACCESSWe report on a detailed study of the irreversibility field Hirr of single crystals of Mg(B1−xCx)2 (x=0, 2, 3.5, 5 and 7.5%) in strong magnetic fields of up to 40 T. Highly sensitive torque measurements revealed that Hirr is greatly enhanced by a factor of two (μ0Hirr(0)\\simeq33 T with x=5%) by carbon substitution compared with that of the pristine MgB2, owing to a reduction in in-plane coherence length. We also observed the temperature-dependent Hirr anisotropy for all carbon contents. This strongly suggests that the two-gap superconductivity of MgB2 is less influenced by a small amount of carbon substitution. We discuss these results by focusing on the impact of carrier doping and impurity scattering on a two-gap superconductor.View full abstractDownload PDF (265K) -
Y. Ihara, K. Ishida, C. Michioka, M. Kato, K. Yoshimura, K. Takada, T. ...2004 Volume 73 Issue 8 Pages 2069-2072
Published: August 15, 2004
Released on J-STAGE: July 25, 2007
JOURNAL RESTRICTED ACCESSWe have performed Co-nuclear quadrupole resonance (NQR) studies on NaxCoO2·yH2O compounds with different Na (x) and hydrate (y) contents. Two samples with different Na contents but nearly the same Tc values (x=0.348, Tc=4.7 K; x=0.339, Tc=4.6 K) were investigated. The spin–lattice relaxation rate 1⁄T1 in the superconducting (SC) and normal states is almost the same for the two samples except just above Tc. NQR measurements were also performed on different-hydrate-content samples with different Tc values, which were prepared from the same Na-content (x=0.348) sample. From measurements of 1⁄T1 using the different-hydrate-content samples, it was found that a low-Tc sample with Tc=3.9 K has a larger residual density of states (DOS) in the SC state and a smaller increase of 1⁄T1T just above Tc than a high-Tc sample with Tc=4.7 K. The former behavior is consistent with that observed in unconventional superconductors, and the latter suggests the relationship between Tc and the increase in DOS just above Tc. This increase, which is seemingly associated with the two-dimensionality of the CoO2 plane, is considered to be one of the most important factors for the occurrence of superconductivity.View full abstractDownload PDF (154K) -
M. Yashima, S. Kawasaki, Y. Kawasaki, G.-q. Zheng, Y. Kitaoka, H. Shis ...2004 Volume 73 Issue 8 Pages 2073-2076
Published: August 15, 2004
Released on J-STAGE: July 25, 2007
JOURNAL RESTRICTED ACCESSWe report the systematic evolution of the superconducting (SC) characteristics of the heavy-fermion (HF) superconductor CeCoIn5 via nuclear-quadrupole-resonance (NQR) measurement under pressure (P). The application of P significantly suppresses the nuclear spin–lattice relaxation rate 1⁄T1 that is dominated by antiferromagnetic (AFM) spin fluctuations (SFs) specific to a quantum critical point (QCP). It is demonstrated that the marked suppression of AFM SFs leads to a reduction in the SC energy gap or in the coupling strength of the Cooper pair. Tc, nevertheless, increases with increasing P due to the increase in HF bandwidth. This is expected to make the lifetime of quasi-particles sufficiently long.View full abstractDownload PDF (146K) -
Hajime Takayama, Koji Hukushima2004 Volume 73 Issue 8 Pages 2077-2080
Published: August 15, 2004
Released on J-STAGE: July 25, 2007
JOURNAL RESTRICTED ACCESSThe spin-glass (SG) states of the three-dimensional Ising Edwards–Anderson model under a static magnetic field h are examined by the standard Monte Carlo simulation of the field-shift aging protocol at temperature T. For each process with (T;tw,h), tw being the waiting time before the field is switched on, we extract the dynamical crossover time, tcr(T;tw,h). We have found a good scaling relation between the two characteristic length scales which are properly determined from tcr and tw and then are normalized by the static field crossover length introduced in the SG droplet theory. This scaling behavior implies the instability of the SG phase in the equilibrium limit even under an infinitesimal h. In comparison with this numerical result the field effect on real spin glasses is also discussed.View full abstractDownload PDF (114K) -
Hiroya Sakurai, Satoshi Takenouchi, Naohito Tsujii, Eiji Takayama-Muro ...2004 Volume 73 Issue 8 Pages 2081-2084
Published: August 15, 2004
Released on J-STAGE: July 25, 2007
JOURNAL RESTRICTED ACCESSPowder NaxCoO2 (0.70≤x≤0.84) samples were synthesized and characterized carefully by X-ray diffraction analysis, inductive-coupled plasma atomic emission spectroscopy, and redox titration. It was proved that γ-NaxCoO2 is formed only in the narrow range of 0.70≤x≤0.78. Nevertheless, the magnetic properties depend strongly on x. We found, for the first time, two characteristic features in the magnetic susceptibility of Na0.78CoO2, a sharp peak at Tp=16 K and an anomaly at Tk=9 K, as well as the transition at Tc=22 K and the broad maximum at Tm=50 K which had already been reported. A type of weak ferromagnetic transition seems to occur at Tk. The transition at Tc, which is believed to be caused by spin density wave formation, was observed clearly for x≥0.74 with constant Tc and Tp independent of x. On the other hand, ferromagnetic moment varies systematically depending on x. These facts suggest the occurrence of a phase separation at the microscopic level, such as the separation into Na-rich and Na-poor domains due to the segregation of Na ions. The magnetic phase diagram and transition mechanism proposed previously should be reconsidered.View full abstractDownload PDF (419K) -
Harukazu Kato, Hironori Sakai, Kenji Ikushima, Shinsaku Kambe, Yo Toku ...2004 Volume 73 Issue 8 Pages 2085-2088
Published: August 15, 2004
Released on J-STAGE: July 25, 2007
JOURNAL RESTRICTED ACCESSDirect AFNMR studies of 235U as well as of 121Sb and 123Sb nuclear spins have been carried out in the antiferromagnetic state of USb2. The central (±\\frac12) 235U peak found at 217.2 MHz passes several identification tests, including the expected very low rate of broadening in an applied field. The 235U hyperfine constant found, 147 T/μB, is within the expected range. This is the first reported observation of 235U NMR in a conducting host material.View full abstractDownload PDF (165K) -
Hiori Kino, Masaru Tateno, Mauro Boero, Jose A. Torres, Takahisa Ohno, ...2004 Volume 73 Issue 8 Pages 2089-2092
Published: August 15, 2004
Released on J-STAGE: July 25, 2007
JOURNAL RESTRICTED ACCESSDNA has recently attracted much attention in view of its possible applications to nano-devices. Despite extensive efforts, however, the experimental results of the electrical conductivity of dry DNA are still rather controversial. In this report, we indicate that a key issue to interpret the experimental results could be the role of counter metal cations, which are expected to alter the electronic properties of pure DNA. In particular, although metallic cations are passivated by hydration, some divalent anhydrous ones originating by drying processes may exist and act as acceptors, doping holes in the host (DNA) HOMO band with the spin distribution localized around the cation. Some consequences relevant to the transport properties are also discussed. The analysis of the various electronic structures presented here will provide a clue for further detailed insights into the transport properties and related mechanisms in DNA chains.View full abstractDownload PDF (113K) -
Tatsuhiro Yogi2004 Volume 73 Issue 8 Pages 2093-2099
Published: August 15, 2004
Released on J-STAGE: July 25, 2007
JOURNAL RESTRICTED ACCESSWe describe the results of numerical calculation for the motion of a top, under taking acount of the sliding friction force between the edge of the top and the floor. New angular velocities \\dotα and \\dotβ are introduced for generating an orthogonal matrix enabling the transformation between principal angular velocities and a set of \\dotα, \\dotθ and \\dotβ. Time derivative of Euler angle \\dotφ is represented by a linear combination of these new angular velocities. This transformation and linear combination allows us to remove the singularities and spurious behavior near Euler angle θ=0 or θ=π and to produce the trajectory of three angular velocities continuously. The orthogonal transformation is successfully introduced to give no difficulty of divergence. A new method is proposed which should lead to correct equations of motion even for a rigid body and provide improved numerical stability and precision for computer simulation studies. Application of this method to the motion of a top enables us to describe time variation of angular velocities, stability of solution for motion and their continuity in real time and space. We also rediscovered the existence of a constant of motion, the so-called Jellett constant, which is independent of the existence of friction and can be written in different forms.View full abstractDownload PDF (257K) -
Bao-Feng Feng, Yusuke Doi, Takuji Kawahara2004 Volume 73 Issue 8 Pages 2100-2111
Published: August 15, 2004
Released on J-STAGE: July 25, 2007
JOURNAL RESTRICTED ACCESSA quasi-continuum model is proposed and studied for the discrete breathers (DBs) or the intrinsic localized modes (ILMs) in one-dimensional anharmonic lattices on the basis of the Padé approximation. Two conservation laws are obtained in the model equation, and the corresponding quantities in discrete system are numerically found to be conserved as well. The exact stationary breather solution is found to the model equation for the Fermi–Pasta–Ulam-β (FPU-β) atomic chains with purely hard quartic anharmonicity, and also found is the approximate stationary breather solution in case the quadratic interaction is included by means of the averaged Lagrangian method. The application of the multiple scales method to the model equation indicates the movability of the breather solutions in the small-amplitude limit. The results of numerical simulations fully support the analytical results mentioned above. A detailed comparison between the FPU-β lattice and its continuum model in properties of the breather collision achieves a good agreement except for a resonant collision case when the discreteness predominates.View full abstractDownload PDF (433K) -
Naoki Kobayashi, Osamu Moriyama, So Kitsunezaki, Yoshihiro Yamazaki, M ...2004 Volume 73 Issue 8 Pages 2112-2116
Published: August 15, 2004
Released on J-STAGE: July 25, 2007
JOURNAL RESTRICTED ACCESSWe have numerically investigated the self-affinity of the bacterial colony model. In order to examine the growth exponent β, we find a new approach to the dynamic scaling hypothesis for the growing rough surface. We have first investigated the self-affinity of the well-known Eden model to check the validity of the new approach. The obtained results of the exponents α≅0.50 and β≅0.33 coincide with the well-known values of the exponents of the Eden model. We have then applied it successfully to growing interfaces produced by the bacterial colony model. We have found that the self-affinity of the bacterial colony model is characterized as α≅0.80 and β≅0.65.View full abstractDownload PDF (771K) -
Myung Ki Cheoun, K. S. Kim2004 Volume 73 Issue 8 Pages 2117-2130
Published: August 15, 2004
Released on J-STAGE: July 25, 2007
JOURNAL RESTRICTED ACCESSPossible ambiguities in the theoretical interpretation of exclusive (e,e′p) reactions are discussed on the basis of realistic model calculations. Gauge ambiguity, medium effects, and contribution of the Δ current are evaluated in distorted wave Born approximation (DWBA) where the four momentum transfer square |qμ|2 is less than 0.5 (GeV/c)2. The gauge ambiguity effects are shown to be about 10% in the small missing momentum region and about 20% maximally in the high missing momentum region. Medium effects of about 6–10% appear mainly in the small missing momentum region. The Δ-resonance current influences the high missing momentum region by about 10% maximally.View full abstractDownload PDF (372K) -
Yueping Niu, Shangqing Gong2004 Volume 73 Issue 8 Pages 2131-2134
Published: August 15, 2004
Released on J-STAGE: July 25, 2007
JOURNAL RESTRICTED ACCESSWe extend the existing theory of stimulated Raman adiabatic passage to a four-level ladder system for realizing superposition of two high-lying Rydberg states by applying a control field to couple them. We find, due to the effect of the control field, that population is completely transferred from the initial level to a superposition of the two high-lying states. Suitable manipulation of the control field and detunings makes it possible to create any coherent superposition states we desired.View full abstractDownload PDF (104K) -
Katsuhiko Sato, Akihiko Toda2004 Volume 73 Issue 8 Pages 2135-2141
Published: August 15, 2004
Released on J-STAGE: July 25, 2007
JOURNAL RESTRICTED ACCESSA simple model for the peeling process of pressure-sensitive adhesive tape is presented. The model consists of linear springs and dashpots and can be solved analytically. Based on the modeling, the curved profile of the peeling tape is spontaneously determined in terms of viscoelastic properties of adhesives. Using this model, two experimental results are discussed: critical peel rates in the peel force and the peel rate dependence of the detachment process of adhesive from the substrate.View full abstractDownload PDF (146K) -
A. M. Siddiqui, T. Hayat, Masood Khan2004 Volume 73 Issue 8 Pages 2142-2147
Published: August 15, 2004
Released on J-STAGE: July 25, 2007
JOURNAL RESTRICTED ACCESSTo understand theoretically the flow properties of physiological fluids, we have considered as a model of the peristaltic motion in a tube, with a sinusoidal wave of small amplitude traveling down its wall. The mathematical model considers a viscous incompressible fluid under the effect of a transverse magnetic field. The wavelength of the traveling wave is taken to be large. The expressions for the stream function, the axial velocity, the pressure gradient and the pressure rise per wavelength have been obtained. The results obtained in the analysis have been evaluated analytically and discussed with the help of graphs. The significance of the Hartmann number has been pointed out by comparing the results with hydrodynamic case. Further, the analogy between the magnetohydrodynamic fluid and hydrodynamic fluid in a porous medium has also been considered.View full abstractDownload PDF (113K) -
Fuyuki Shimojo, Masaru Aniya, Kozo Hoshino2004 Volume 73 Issue 8 Pages 2148-2153
Published: August 15, 2004
Released on J-STAGE: July 25, 2007
JOURNAL RESTRICTED ACCESSThe structural and electronic properties of molten CuI are studied by means of ab initio molecular-dynamics simulations. From the first-peak positions of the partial pair distribution functions, we confirm that the nearest-neighbor distance for Cu–Cu pair is almost the same as that for Cu–I pair in spite of the correlation between the same type of ions. It is shown that there exists a large fluctuation in the partial atomic concentration of Cu ions to retain the anomalously short Cu–Cu distance, while iodine ions distribute uniformly. It is clarified by the population analysis that there is a covalent-like bonding between neighboring Cu ions as well as between Cu and I ions.View full abstractDownload PDF (224K) -
Masashi Torikai, Mamoru Yamashita2004 Volume 73 Issue 8 Pages 2154-2157
Published: August 15, 2004
Released on J-STAGE: July 25, 2007
JOURNAL RESTRICTED ACCESSPhase behaviours of liquid crystals under external fields, conjugate to the nematic order and smectic order, are studied within the framework of mean field approximation developed by McMillan. It is found that phase diagrams, of temperature vs interaction parameter of smectic A order, show several topologically different types caused by the external fields. The influences of the field conjugate to the smectic A phase, which is fictitious field, are precisely discussed.View full abstractDownload PDF (99K) -
V. Koteski, N. Ivanovic, B. Cekic, Z. Miloševic2004 Volume 73 Issue 8 Pages 2158-2163
Published: August 15, 2004
Released on J-STAGE: July 25, 2007
JOURNAL RESTRICTED ACCESSA detailed theoretical study of the structure, electronic properties, and the electric field gradients of the Hf2Ni intermetallic compound is presented. Using all-electron full-potential linearized augmented plane wave (FP-LAPW) formalism, the equilibrium volume, bulk moduli, charge density, and electric field gradients are calculated and compared with the available experimental and with other theoretical results. The lattice relaxation and the supercell calculations are found to be essential for the correct interpretation of the experimental results.View full abstractDownload PDF (1570K) -
H. Obuse, K. Yakubo2004 Volume 73 Issue 8 Pages 2164-2168
Published: August 15, 2004
Released on J-STAGE: July 25, 2007
JOURNAL RESTRICTED ACCESSWe study the box-measure correlation function of quantum states at the Anderson transition point with taking care of anomalously localized states (ALS). By eliminating ALS from the ensemble of critical wavefunctions, we confirm, for the first time, the scaling relation z(q)=d+2τ(q)−τ(2q) for a wide range of q, where q is the order of box-measure moments and z(q) and τ(q) are the correlation and the mass exponents, respectively. The influence of ALS to the calculation of z(q) is also discussed.View full abstractDownload PDF (148K) -
Naokazu Shibata, Daijiro Yoshioka2004 Volume 73 Issue 8 Pages 2169-2173
Published: August 15, 2004
Released on J-STAGE: July 25, 2007
JOURNAL RESTRICTED ACCESSThe transition between the stripe state and the liquid state in a high magnetic field is studied by the density-matrix renormalization-group (DMRG) method. Systematic analysis on the ground state of two-dimensional electrons in the lowest Landau level shows that the transition from the stripe state to the liquid state at ν∼3⁄8 is caused by a reduction of repulsive interaction around r∼3l. The same reduction of the interaction also stabilizes the incompressible liquid states at ν=1⁄3 and 2⁄5, which shows a similarity between the two liquid states at ν∼3⁄8 and 1⁄3. It is also shown that the strong short-range interaction around r∼l in the lowest Landau level makes qualitatively different stripe correlations compared with that in higher Landau levels.View full abstractDownload PDF (166K) -
Masato Morifuji2004 Volume 73 Issue 8 Pages 2174-2181
Published: August 15, 2004
Released on J-STAGE: July 25, 2007
JOURNAL RESTRICTED ACCESSA transport theory for semiconductors based on real space motion of a wavepacket is developed. It is shown that, in an electric field, a wavepacket is formed as a result of interference and that transport can be described as position changes of the wavepacket regardless of strength of the electric field. We also show that use of wavepackets for transport results in quantum effects such as intracollisional field effect due to finite scattering duration. Results of analysis for miniband transport are shown to indicate validity and usefulness of the present theory.View full abstractDownload PDF (187K) -
J. A. Torres, J. J. Sáenz2004 Volume 73 Issue 8 Pages 2182-2193
Published: August 15, 2004
Released on J-STAGE: July 25, 2007
JOURNAL RESTRICTED ACCESSWe consider the generalized scattering matrix method for the solution of 3D scattering problems that can be well described by Helmholtz equation. A set of optimum strategies for the transversal basis selection, as well as for the mode matching algebra, are proposed; with them, a triple goal is achieved: to optimize the formulation, to simplify the implementation, and to increase computational speed. The proposed matrix truncation method provides quick convergence with one single parameter to be tuned. The matrix algebra used provides excellent stability vs the number of junctions as well as great computational speed. As illustrations and test, using the improved method, some aspects of the electronic transport through ballistic contacts are studied. Current vortex-rings in narrow–wide connections are predicted. A simple physical picture for the understanding of increasing conductance while pulling ideal monoatomic metal wires is proposed.View full abstractDownload PDF (997K) -
Koichi Akimoto, Tsuneya Ando2004 Volume 73 Issue 8 Pages 2194-2200
Published: August 15, 2004
Released on J-STAGE: July 25, 2007
JOURNAL RESTRICTED ACCESSNumerical calculations of the conductance are performed to study effects of trigonal warping of bands on a perfectly conducting channel in metallic carbon nanotubes existing unless the potential range of scatterers is smaller than the lattice constant. The perfect channel can easily be destroyed in the presence of small amount of trigonal warping when there are several bands at the energy, while it is much more robust in the energy range of metallic linear bands.View full abstractDownload PDF (192K) -
Takeshi Inaoka2004 Volume 73 Issue 8 Pages 2201-2211
Published: August 15, 2004
Released on J-STAGE: July 25, 2007
JOURNAL RESTRICTED ACCESSUsing the time-dependent local-density approximation, we investigate low-dimensional plasmons (PL’s) in a metallic strip monolayer on a semiconductor surface. We find a series of PL dispersion branches where the node number in oscillation of the induced electron density δn across the strip increases one by one with rising energy. The 0-node and 1-node modes are edge PL’s with different parity in the δn distribution. In each PL branch with a larger node number, character of area PL starts to appear with an increase in wave number q. In a broad q region, we examine the energy-loss intensity, the energy dispersion, and the δn distribution in each mode. Our analysis shows how dramatically the δn distribution of the PL mode evolves with change in q, and how the character of the δn distribution is correlated with the energy-loss intensity.View full abstractDownload PDF (277K) -
Takuo Ohkochi, Nobuyoshi Hosoito, Ko Mibu, Hiroo Hashizume2004 Volume 73 Issue 8 Pages 2212-2218
Published: August 15, 2004
Released on J-STAGE: July 25, 2007
JOURNAL RESTRICTED ACCESSThe induced magnetic polarization in nonmagnetic layers and its relationship with the magnetization in ferromagnetic layers are investigated for Gd/Cu multilayers with X-ray magnetic circular dichorism (XMCD). The XMCD measurements show that the peak intensities at the Cu K-edge decrease in proportion to those at the Gd L3-edge as the temperature increases. The overall shape of the XMCD spectra at the Cu K-edge, on the other hand, does not change. These results suggest that the size of the magnetic polarization in the Cu layers changes but the depth profile remains unchanged when the Gd magnetization varies in size. The XMCD spectra at the Cu K-edge are composed of several positive and negative peaks. A possible origin of the specific shape of the spectra is discussed.View full abstractDownload PDF (623K) -
Kiwamu Kudo, Kosaku Yamada2004 Volume 73 Issue 8 Pages 2219-2231
Published: August 15, 2004
Released on J-STAGE: July 25, 2007
JOURNAL RESTRICTED ACCESSIn order to explain how impurities affect the unconventional superconductivity, we study non-magnetic impurity effect on the transition temperature using on-site U Hubbard model within a fluctuation exchange (FLEX) approximation. We find that in appearance, the reduction of Tc roughly coincides with the well-known Abrikosov–Gor’kov formula. This coincidence results from the cancellation between two effects; one is the reduction of attractive force due to randomness, and another is the reduction of the damping rate of quasi-particle arising from electron interaction. As another problem, we also study impurity effect on underdoped cuprate as the system showing pseudogap phenomena. To the aim, we adopt the pairing scenario for the pseudogap and discuss how pseudogap phenomena affect the reduction of Tc by impurities. We find that ‘pseudogap breaking’ by impurities plays the essential role in underdoped cuprate and suppresses the Tc reduction due to the superconducting (SC) fluctuation.View full abstractDownload PDF (503K) -
Toshiaki Matsuzaki, Naoki Momono, Migaku Oda, Masayuki Ido2004 Volume 73 Issue 8 Pages 2232-2238
Published: August 15, 2004
Released on J-STAGE: July 25, 2007
JOURNAL RESTRICTED ACCESSTo examine the so-called small pseudogap and the superconducting (SC) condensation energy U(0), the electronic specific heat Cel was measured on La2−xSrxCuO4 up to ∼120 K. In samples with doping level p (=x) less than ∼0.2, small pseudogap behavior appears in the γ (=Cel⁄T) vs T curve around the mean-field critical temperature for a d-wave superconductor Tco (=2Δ0⁄(4–5)kB), where Δ0 is the maximum gap at T<<Tc. The condensation energy U(0) is largely reduced in the pseudogap regime (p\\lesssim0.2). The reduction of U(0) can be well reproduced by introducing an effective SC energy scale Δ0eff=βpΔ0 (β=4.5) instead of Δ0. The effective SC energy scale is discussed in relation to the coherent pairing gap formed over the nodal Fermi arc.View full abstractDownload PDF (1019K) -
Koichi Watanabe, Takafumi Kita2004 Volume 73 Issue 8 Pages 2239-2244
Published: August 15, 2004
Released on J-STAGE: July 25, 2007
JOURNAL RESTRICTED ACCESSWe study nonmagnetic impurity effects in MgB2 using the quasiclassical equations of superconductivity for a weak-coupling two-band model. Parameters in the model are fixed so as to reproduce experiments on MgB2 as closely as possible. The quasiparticle density of states and the specific heat are calculated for various values of the interband impurity scattering. The density of states changes gradually from a two-gap structure into the conventional single-gap structure as the interband scattering increases. It is found that the excitation threshold is not a monotonic function of the interband scattering. Calculated results for the specific heat are in good agreements with experiments on samples after irradiation.View full abstractDownload PDF (406K) -
Tomo Munehisa, Yasuko Munehisa2004 Volume 73 Issue 8 Pages 2245-2251
Published: August 15, 2004
Released on J-STAGE: July 25, 2007
JOURNAL RESTRICTED ACCESSIn this paper we propose the recursive stochastic state selection method, an extension of the recently developed stochastic state selection method in Monte Carlo calculations for quantum spin systems. In this recursive method we use intermediate states to define probability functions for stochastic state selections. Then we can diminish variances of samplings when we calculate expectation values of the powers of the Hamiltonian. In order to show the improvement we perform numerical calculations of the spin-1⁄2 anti-ferromagnetic Heisenberg model on the triangular lattice. Examining results on the ground state of the 21-site system we confide this method in its effectiveness. We also calculate the lowest and the excited energy eigenvalues as well as the static structure factor for the 36-site system. The maximum number of basis states kept in a computer memory for this system is about 3.6×107. Employing a translationally invariant initial trial state, we evaluate the lowest energy eigenvalue within 0.5% of the statistical errors.View full abstractDownload PDF (130K) -
Masakazu Ito, Koji Asada, Yuko Nakamori, Jyun’ya Hori, Hironobu ...2004 Volume 73 Issue 8 Pages 2252-2256
Published: August 15, 2004
Released on J-STAGE: July 25, 2007
JOURNAL RESTRICTED ACCESSWe report the transport and thermodynamic properties under hydrostatic pressure in the antiferromagnetic Kondo compound CeMg2Cu9 with a two-dimensional arrangement of Ce atoms. Magnetic specific heat Cmag(T) shows a Schottky-type anomaly around 30 K originating from the crystal electric field (CEF) splitting of the 4f state with the first excited level at Δ1⁄kB=58 K and the second excited level at Δ2⁄kB=136 K from the ground state. Electric resistivity shows a two-peak structure due to the Kondo effect on each CEF level around T1max=3 K and T2max=40 K. These peaks merge around 1.9 GPa with compression. With increasing pressure, Néel temperature TN initially increases and then changes to decrease. TN finally disappears at a quantum critical point Pc=2.4 GPa.View full abstractDownload PDF (238K) -
Ryousuke Shiina2004 Volume 73 Issue 8 Pages 2257-2265
Published: August 15, 2004
Released on J-STAGE: July 25, 2007
JOURNAL RESTRICTED ACCESSLow-lying singlet–triplet crystal-field levels are realized in Pr-based filled-skutterudite compounds. The properties of multipolar moments in such systems are studied theoretically to elucidate the microscopic origin of their anomalous ordered states. First, we introduce a proper set of multipoles to express the active degrees of freedom in the singlet–triplet subspace. Then, a group-theoretical classification of multipoles is presented to discuss the nature of mixed order parameters in zero and finite magnetic fields. Using a pseudo-spin representation, we construct a generic form of pair interactions and identify the sources of anisotropy for directions of magnetic field. The interactions and the phase diagram of PrOs4Sb12, which is a typical singlet–triplet system, are discussed in connection with the Th symmetry specific to the filled-skutterudite systems.View full abstractDownload PDF (212K) -
Mineko Yamada, Yoshiko Obiraki, Tomoyuki Okubo, Tomoyuki Shiromoto, Yu ...2004 Volume 73 Issue 8 Pages 2266-2275
Published: August 15, 2004
Released on J-STAGE: July 25, 2007
JOURNAL RESTRICTED ACCESSWe have grown a single crystal of PrRh3B2 with the hexagonal structure and measured the electrical resistivity, specific heat, de Haas–van Alphen oscillation, magnetic susceptibility, high-field magnetization, thermal expansion and magnetostriction. PrRh3B2 is not a simple ferromagnet as reported previously, but a ferrimagnet with an ordering temperature Tord=3.6 K. The Schottky specific heat observed around 25 K and the large anisotropy of the magnetic susceptibility and magnetization are found to be well explained by the crystalline electric field (CEF) with a large overall CEF-splitting energy of 1080 K and a strong ferromagnetic exchange interaction along the [0001] direction. The topology of the Fermi surface in PrRh3B2 is similar to that of the non-4f reference compound LaRh3B2, exhibiting a quasi-one-dimensional character of the electronic states.View full abstractDownload PDF (2670K) -
Yusuke Okuda, Tetsuya Takeuchi, Takeshi Yamamoto, Daisuke Honda, Hiroa ...2004 Volume 73 Issue 8 Pages 2276-2282
Published: August 15, 2004
Released on J-STAGE: July 25, 2007
JOURNAL RESTRICTED ACCESSWe measured the electrical resistivity, specific heat, magnetic susceptibility, high-field magnetization, thermal expansion and magnetostriction of an antiferromagnet Ce3Sn7 with the orthorhombic crystal structure. The experimental data are found to be well explained on the basis of the crystalline electric field (CEF) 4f-scheme previously proposed by Bonnet et al. in which the two Ce atoms at the 2(a) site possess a magnetic moment of 0.36 μB/Ce and the one Ce atom at the 4(i) site possesses no magnetic moment as in a valence fluctuating compound CeSn3. We also constructed the antiferromagnetic phase diagram for the three principal directions. Furthermore, we carried out the de Haas–van Alphen experiment. Fermi surfaces are many in number but extremely small in volumes, indicating that Ce3Sn7 is a semimetal.View full abstractDownload PDF (1918K) -
Tomohiko Nakajima, Hideki Yoshizawa, Yutaka Ueda2004 Volume 73 Issue 8 Pages 2283-2291
Published: August 15, 2004
Released on J-STAGE: July 25, 2007
JOURNAL RESTRICTED ACCESSThe discovery of novel structural and physical properties in the A-site ordered manganite RBaMn2O6 (R=Y and rare earth elements) has demanded new comprehension about perovskite manganese oxides. In the present study, the A-site disordered form, R0.5Ba0.5MnO3, has been investigated and compared with both RBaMn2O6 and R0.5A0.5MnO3 (A: Sr, Ca) in the structures and electromagnetic properties. R0.5Ba0.5MnO3 has a primitive cubic perovskite cell in the structure and magnetic glassy states are dominant as its ground state, in contrast to the ordinary disordered R0.5A0.5MnO3 (A: Sr, Ca). In Pr-compounds with various degrees of Pr/Ba randomness at the A-sites, the A-site disorder gradually suppresses both ferromagnetic and A-type antiferromagnetic transitions and finally leads to a magnetic glassy state in Pr0.5Ba0.5MnO3. A peculiar behavior, multi-step magnetization and resistivity change, has been observed in Pr0.5Ba0.5MnO3. These properties could be closely related to any spatial heterogeneity caused by the random distribution of Ba2+ and R3+ with much different ionic radius.View full abstractDownload PDF (2386K) -
Rifki Muhida, Wilson Agerico Diño, Md. Mahmudur Rahman, Hideaki ...2004 Volume 73 Issue 8 Pages 2292-2295
Published: August 15, 2004
Released on J-STAGE: July 25, 2007
JOURNAL RESTRICTED ACCESSWe investigate the spin polarization of a multiple-decked sandwich cluster, viz., Mn(C6H6)n+1. As a first step, we consider Mn(C6H6)n+1 clusters with n=1 and M = Mn, Fe, Co. Based on the density functional theory, we find an increase in the magnetic moment of the benzene clusters, and a decrease in the magnetic moment of M in the M(C6H6)2 systems. From increased magnetic moment of benzenes, we find a way to inject spin to benzenes through 2pz orbitals.View full abstractDownload PDF (137K) -
Kazuo Hida2004 Volume 73 Issue 8 Pages 2296-2304
Published: August 15, 2004
Released on J-STAGE: July 25, 2007
JOURNAL RESTRICTED ACCESSGround state properties of the S=1⁄2 antiferromagnetic XXZ chain with Fibonacci exchange modulation are studied using the real space renormalization group method for strong modulation. The quantum dynamical critical behavior with a new universality class is predicted in the isotropic case. Combining our results with the weak coupling renormalization group results by Vidal et al., the ground state phase diagram is obtained.View full abstractDownload PDF (243K) -
Tetsuya Hama, Masahiro Matsumura, Harukazu Kato, Hideki Yamagata, Yoh ...2004 Volume 73 Issue 8 Pages 2305-2312
Published: August 15, 2004
Released on J-STAGE: July 25, 2007
JOURNAL RESTRICTED ACCESS55Mn NQR measurements at the Mn-II site in a polycrystalline β-Mn have been performed over the wide temperature range up to 300 K. Fine structures in the NQR spectrum are newly observed below 100 K, indicating that a sufficiently large region of the sample has an antiferromagnetic moment with a small magnitude of ∼10−4μB. Taking account of the fact that the spectral shape depends on the sample particle size, we suggest that the surfaces of the sample particles affect the electronic ground state of β-Mn and that the staggered moment extends within 3 μm depth from the surface. A role of the geometrical frustration is discussed. The nuclear spin–lattice relaxation rate 1⁄T1 and the spin–spin relaxation rate 1⁄T2 increase divergently at high temperatures, implying quadrupole relaxation arising from lattice vibrations.View full abstractDownload PDF (320K) -
Kazuyuki Takeda, K. Takegoshi, Takehiko Terao2004 Volume 73 Issue 8 Pages 2313-2318
Published: August 15, 2004
Released on J-STAGE: July 25, 2007
JOURNAL RESTRICTED ACCESSA high 1H polarization of 0.7 is attained at 105 K in a 0.32 T field by dynamic nuclear polarization using electron spins in the photoexcited triplet state. In a single crystal sample of 0.018 mol% pentacene-doped naphthalene, the 1H polarization is built up to the ultimate value attainable by this method, corresponding to a 2.1×105-fold enhancement of 1H polarization as compared to the thermal equilibrium polarization. The experimental strategies and possible applications as well as extensions of this approach are discussed.View full abstractDownload PDF (106K) -
Kazuyuki Takeda, K. Takegoshi, Takehiko Terao2004 Volume 73 Issue 8 Pages 2319-2322
Published: August 15, 2004
Released on J-STAGE: July 25, 2007
JOURNAL RESTRICTED ACCESSExperiments of dynamic nuclear polarization by electron spins in the photoexcited triplet state were made using single crystal and polycrystalline samples of 99.21%-deuterated naphthalene doped with 0.015 mol% pentacene. In the single crystal sample, the polarization of the residual protons was built up to 0.7 at 105 K, reaching the ultimate polarization equal to the photo-induced electron spin polarization. A doublet due to the two protons which happen to be adjacent to each other in a deuterated naphthalene molecule was observed in the single crystal under deuteron double-quantum decoupling; it exhibits polarization-induced asymmetry when observed by a small-tip angle pulse. In the polycrystalline sample the resultant 1H polarization was 0.033. The 1H NMR lineshape under deuteron decoupling in the single crystal and the inhomogeneous 1H distribution in a deuterated naphthalene molecule are discussed.View full abstractDownload PDF (94K) -
Dispersion Relation of the Third Order Nonlinear Dielectric Susceptibility in Poly-dispersive SystemYoshihiro Ishibashi, Hiroshi Orihara, Rasa Pirc, Robert Blinc2004 Volume 73 Issue 8 Pages 2323-2325
Published: August 15, 2004
Released on J-STAGE: July 25, 2007
JOURNAL RESTRICTED ACCESSAn expression of a third order nonlinear susceptibility of the poly-dispersive system with the distributed relaxation times is derived for the relaxational system where the linear dielectric susceptibility formula of the Cole–Cole type applies. It has turned out that the parameter β, specifying the distribution of the relaxation times, appears as the amplitude of the higher order dielectric susceptibility.View full abstractDownload PDF (68K) -
Takashi Yamamoto, Kyuya Yakushi, Yasuhiro Shimizu, Gunzi Saito2004 Volume 73 Issue 8 Pages 2326-2332
Published: August 15, 2004
Released on J-STAGE: July 25, 2007
JOURNAL RESTRICTED ACCESSThe polarized Raman and infrared spectra of θ-(ET)2Cu2CN[N(CN)2]2 [ET = bis(ethylenedithio)tetrathiafulvalene] were measured at various temperatures below 300 K. We investigated the three C=C stretching modes, v2, v3 and v27. The spectral pattern is compatible with the horizontally charge-ordered state, where the site-charge distributions are +0.17 and +0.83. We have found that the vibronic v3 bands correlate to the dihedral angles, \\varphi, in the θ-ET salts. This relation is well reproduced by the numerical calculation based on the cluster model with C2 symmetry. The spectral features suggest the dynamical fluctuation of nearly localized charges even above its phase transition temperature, ∼220 K.View full abstractDownload PDF (180K) -
Tomomi Tao, Hiroyuki Nakagawa, Masato Yamasaki, Hiraku Nishimori2004 Volume 73 Issue 8 Pages 2333-2341
Published: August 15, 2004
Released on J-STAGE: July 25, 2007
JOURNAL RESTRICTED ACCESSUsing a simple model for the trail formation of ants, the relation between i) the schedule of feeding which represents the unsteady natural environment, ii) emerging patterns of trails connecting a nest with food resources, and iii) the foraging efficiency is studied. Simulations and a simple analysis show that the emergent trail pattern flexibly varies depending on the feeding schedule by which ants can make an efficient foraging according to the underlying unsteady environment.View full abstractDownload PDF (185K) -
Yoshihiro Yamazaki, Akihiko Toda2004 Volume 73 Issue 8 Pages 2342-2346
Published: August 15, 2004
Released on J-STAGE: July 25, 2007
JOURNAL RESTRICTED ACCESSWe investigated (i) the relationship between the spatiotemporal pattern of a deformed adhesive and peel load during peeling, and (ii) the dependence of the pattern formation on peel speed in the hard spring limit case. In the hard spring limit case, it is found that elastic and viscous peeling states coexist. It is also found that the occupation ratio of tunnel structures in a separation front is determined by the peel speed and is a monotonically decreasing function of peel speed. We experimentally confirmed that the value of peel load has a linear dependence on the occupation ratio of tunnel structures. An explanation of dynamical behavior is also given on the basis of the creation–annihilation dynamics of tunnel structures.View full abstractDownload PDF (228K)