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Volume 72, Issue 11
Displaying 1-45 of 45 articles from this issue
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Masato Makino, Masao Doi2003 Volume 72 Issue 11 Pages 2699-2701
Published: November 15, 2003
Released on J-STAGE: July 25, 2007
JOURNAL RESTRICTED ACCESSWe present an analysis on the sedimentation of a propeller-like particle in Newtonian fluid. Due to the translation–rotation coupling, the propeller-like particle settles down with nonconstant speed, drawing a rather complex trajectory. We give analytic expressions for the orientation and the height of the particle using elliptic functions and integrals. We found that the motion of the propeller-like particle remains in the finite region in the X–Y plane (the plane normal to the direction of sedimentation). This is in contrast to the ellipsoidal particle which does not have the translation–rotation coupling, and moves with constant velocity in the X–Y plane.View full abstractDownload PDF (302K) -
Fuyuki Shimojo, Masaru Aniya2003 Volume 72 Issue 11 Pages 2702-2705
Published: November 15, 2003
Released on J-STAGE: July 25, 2007
JOURNAL RESTRICTED ACCESSThe dynamic properties of mobile Cu ions in the superionic conductor CuI are studied by ab initio molecular-dynamics simulations. To investigate the bonding nature of the material, the gross charge of each ion and the overlap population between each Cu–I pair are calculated by the population analysis as a function of time. It is shown that the covalent bonding around the Cu ions weakens when they diffuse in the octahedron cage during the migration between neighboring tetrahedral sites. It is also shown that the ionicities of the Cu ions at the octahedral sites are larger than those of the Cu ions at the tetrahedral sites. These results clearly reveal that the time evolution of local bonding plays an important role in high ionic conductivity.View full abstractDownload PDF (196K) -
Muneo Sugiura, Yoshikazu Suzumura2003 Volume 72 Issue 11 Pages 2706-2709
Published: November 15, 2003
Released on J-STAGE: July 25, 2007
JOURNAL RESTRICTED ACCESSThe transition temperature, Tc, of the spin–Peierls state has been examined for one-dimensional half-filled electron systems with the repulsive interactions of the on site (U) and nearest-neighbor site (V). We calculate Tc on the plane of U and V by considering two kinds of states, namely, bond alternation and site alternation, of the charge density wave. Based on the bosonization and the renormalization group method, it is found that Tc of the bond alternation is dominant for U\\gtrsim2V and takes a maximum for V\\simeqU⁄2 while Tc of the site alternation is dominant for U\\lesssim2V and increases monotonically with increasing V. The ratio of the charge gap to Tc is large for the former state while it is of the order of unity for the latter state. Based on the results, spin–Peierls states in organic conductors are discussed.View full abstractDownload PDF (148K) -
Yositake Takane, Katsunori Wakabayashi2003 Volume 72 Issue 11 Pages 2710-2713
Published: November 15, 2003
Released on J-STAGE: July 25, 2007
JOURNAL RESTRICTED ACCESSThe properties of quantum electron transport through metallic carbon nanotubes with several conducting channels are investigated by the random-matrix approach. Starting from the unique scattering symmetry observed in metallic carbon nanotubes with long-range impurity potential, we can derive the random-matrix representation in which the classical and quantum processes are clearly separated. With increasing system length, the system approaches a fixed point, where only one channel is perfectly conducting and other channels are completely closed. It is shown that such behavior should be attributed to the antilocalization effect. We can describe the decoherence effect on the total transmission probability ⟨T⟩ within the random-matrix theory. For a nanotube of length L, we obtain ⟨T⟩∼Lφ⁄L for l\\lesssimLφ<<L, where l and Lφ are the mean free path and the phase coherence length, respectively.View full abstractDownload PDF (78K) -
Naoki Toyota, Yasunori Abe, Takahiko Kuwabara, Eiichi Negishi, Hiroshi ...2003 Volume 72 Issue 11 Pages 2714-2717
Published: November 15, 2003
Released on J-STAGE: July 25, 2007
JOURNAL RESTRICTED ACCESSWe have studied magnetic field effects on the nonlinear electrical transport associated with a negative resistance and switching phenomena in an antiferromagnetic insulating (AFI) ground state of the title π–d coupled conductor below the metal-to-insulator transition temperature TMI=8.3 K. The overall characteristics of current density (J) versus electric field (E) are well reproduced by an empirical formula with a current-density-dependent conductivity proportional to Jn; if n>1, a negative resistance effect (dJ⁄dE<0) appears above threshold JT, while, if n<1, a monotonic nonlinear resistance (dJ⁄dE>0) appears. With increasing magnetic field, there appears a crossover from n>1 to n<1 around H*\\simeq7 T, followed by a conventional ohmic transport at fields higher than the critical magnetic field HC=10.6 T at 4.2 K for the reentrant metallic transition. A switching phenomenon, which always occurs at J<JT in the well-ordered AFI states, triggers a discontinuous transition from low-conductivity to high-conductivity states, followed by the negative resistance at J>JT which can be ascribed to a carrier’s self-decondensation process.View full abstractDownload PDF (388K) -
Victor Ryzhii, Akira Satou2003 Volume 72 Issue 11 Pages 2718-2721
Published: November 15, 2003
Released on J-STAGE: July 25, 2007
JOURNAL RESTRICTED ACCESSWe calculate the current–voltage characteristics of a two-dimensional electron system (2DES) subjected to a magnetic field at strong electric fields. The interaction of electrons with piezoelectric acoustic phonons is considered to be a major scattering mechanism governing the current–voltage characteristics. It is shown that at a sufficiently strong electric field corresponding to the Hall drift velocity exceeding the velocity of sound, the dissipative current exhibits an overshoot. The overshoot of the dissipative current can result in a breakdown of the absolute negative conductivity caused by microwave irradiation and, therefore, can substantially affect the formation of the domain structures with the so-called zero-resistance and zero-conductance states and supersonic electron streams.View full abstractDownload PDF (127K) -
Masaharu Matsunami, Hidekazu Okamura, Takao Nanba, Hitoshi Sugawara, H ...2003 Volume 72 Issue 11 Pages 2722-2725
Published: November 15, 2003
Released on J-STAGE: July 25, 2007
JOURNAL RESTRICTED ACCESSWe have studied the optical conductivity of the filled skutterudite CeOs4Sb12. The optical conductivity spectra show a strong temperature dependence and reveal an energy gap of ∼30 meV below 60 K. This shows that the density of states near the Fermi level of CeOs4Sb12 is strongly reduced. In addition to the gap formation, a pronounced peak is observed at ∼70 meV below 160 K. This mid-infrared peak is interpreted in terms of optical excitations across a hybridization gap consisting of conduction- and f-electron states. The observed characteristics in the optical spectra are quite similar to those previously reported for Kondo semiconductors. We compare the optical characteristics of CeOs4Sb12 found in the present work with other physical properties, and analyze its electronic structures.View full abstractDownload PDF (201K) -
Toshifumi Itakura, Yasuhiro Tokura2003 Volume 72 Issue 11 Pages 2726-2729
Published: November 15, 2003
Released on J-STAGE: July 25, 2007
JOURNAL RESTRICTED ACCESSWe examine the dephasing rate of a Josephson charge qubit system due to background charge fluctuations.We consider single qubit and two-charge traps. The transition probability was controlled to a state where two traps were occupied. The transition probability was affected by the Coulomb blockade effect that occurs between two charge traps. To obtain the dephasing rate, we computed the spectra of random frequency modulation signals. Our results show that the interaction between charge traps suppresses dephasing.View full abstractDownload PDF (117K) -
Yushun Wang, Bin Wang, Zhongzhen Ji, Mengzhao Qin2003 Volume 72 Issue 11 Pages 2731-2736
Published: November 15, 2003
Released on J-STAGE: July 25, 2007
JOURNAL RESTRICTED ACCESSIn this paper, taking the sine-Gordon equation as an example, we present a new method to construct the symplectic schemes for Hamilton PDEs. Different from the previous symplectic methods dealing with PDEs, our method is that to view the PDEs as a Hamilton system in Banach space, then to apply the generating functions method to the Hamilton system. After overcoming successfully the essential difficulties on the calculations of high order variation derivatives, we get the semi-discrete difference schemes for the PDEs with arbitrary order of accuracy in time direction. Furthermore the corresponding modified equations of the infinite dimensional Hamiltonian system are obtained from the semi-discretization. We use the central difference operators to discretize the derivatives in space. Thus the resulting full discrete symplectic schemes can be of any order accuracy. Numerical results on collisions of solitons are also presented to show the effectiveness of the schemes.View full abstractDownload PDF (1365K) -
Tamás Fülöp, Izumi Tsutsui, Taksu Cheon2003 Volume 72 Issue 11 Pages 2737-2746
Published: November 15, 2003
Released on J-STAGE: July 25, 2007
JOURNAL RESTRICTED ACCESSWe investigate the spectral and symmetry properties of a quantum particle moving on a circle with a pointlike singularity (or point interaction). We find that, within the U(2) family of the quantum mechanically allowed distinct singularities, a U(1) equivalence (of duality-type) exists, and accordingly the space of distinct spectra is U(1)×[SU(2)⁄U(1)], topologically a filled torus. We explore the relationship of special subfamilies of the U(2) family to corresponding symmetries, and identify the singularities that admit an N=2 supersymmetry. Subfamilies that are distinguished in the spectral properties or the WKB exactness are also pointed out. The spectral and symmetry properties are also studied in the context of the circle with two singularities, which provides a useful scheme to discuss the symmetry properties on a general basis.View full abstractDownload PDF (161K) -
Hussein Farrokhpour, Gholamabbas Parsafar2003 Volume 72 Issue 11 Pages 2747-2753
Published: November 15, 2003
Released on J-STAGE: July 25, 2007
JOURNAL RESTRICTED ACCESSA new potential function, which can in a simple and reasonable manner represent the molecular interaction of many kinds of hard-core fluids by varying the value of its parameter, is proposed. For prediction of thermodynamic properties of hard-core fluids such as the square-well (SW) and hard core Lennard–Jones (HCLJ), a simple perturbed equation of state (EOS) is derived by using the new potential function along with the Barker–Henderson perturbation theory. This method yields a simple and general analytical expression for each thermodynamic property of such fluids. The most important feature of these expressions is that they have no adjustable parameter and in some regions in which there is no simulation data for such hard-core fluids, such equation may be used to predict the needed data. The derived EOS in this work was successfully applied to predict thermodynamic properties of the SW and HCLJ fluids, for which the simulation data are available. The predicted results are in good agreement with both the computer simulation data and the well-known equations of state.View full abstractDownload PDF (102K) -
Akiko Okumura, Shin-ichi Tadaki2003 Volume 72 Issue 11 Pages 2754-2758
Published: November 15, 2003
Released on J-STAGE: July 25, 2007
JOURNAL RESTRICTED ACCESSThe optimal velocity (OV) model is one of car-following traffic flow models, which can reproduce some observed features of the traffic flow on expressways. The acceleration and braking abilities are symmetrically introduced into the OV model, besides the asymmetry in real vehicles. We introduce the asymmetry between acceleration and braking through the difference of the susceptibility in the OV model. As a result, the density contrast becomes large between inside and outside of jam clusters. Jam clusters propagate slower than in the symmetric case.View full abstractDownload PDF (282K) -
Tomo Munehisa, Yasuko Munehisa2003 Volume 72 Issue 11 Pages 2759-2765
Published: November 15, 2003
Released on J-STAGE: July 25, 2007
JOURNAL RESTRICTED ACCESSWe propose a new type of Monte Carlo approach in numerical studies of quantum systems. Introducing a probability function which determines whether a state in the vector space survives or not, we can evaluate expectation values of powers of the Hamiltonian from a small portion of the full vector space. This method is free from the negative sign problem because it is not based on importance sampling techniques. In this paper we describe our method and, in order to examine how effective it is, present numerical results on the 4×4, 6×6 and 8×8 Heisenberg spin one-half model. The results indicate that we can perform useful evaluations with limited computer resources. An attempt to estimate the lowest energy eigenvalue is also stated.View full abstractDownload PDF (122K) -
Akihisa Kohama, Ryoichi Seki, Akito Arima, Shuhei Yamaji2003 Volume 72 Issue 11 Pages 2766-2780
Published: November 15, 2003
Released on J-STAGE: July 25, 2007
JOURNAL RESTRICTED ACCESSWe demonstrate that the matter density distribution in the surface region is determined well by the use of the relatively low-intensity beams that become available at the upcoming radioactive beam facilities. Following the method used in the analyses of electron scattering, we examine how well the density distribution is determined in a model-independent way by generating pseudo data and by carefully applying statistical and systematic error analyses. We also study how the determination becomes deteriorated in the central region of the density, as the quality of data decreases. Determination of the density distributions of neutron-rich nuclei is performed by fixing parameters in the basis functions to the neighboring stable nuclei. The procedure allows that the knowledge of the density distributions of stable nuclei assists to strengthen the determination of their unstable isotopes.View full abstractDownload PDF (884K) -
Kimitaka Itoh, Sanae-I. Itoh, Nobumitsu Yokoi, Akira Yoshizawa2003 Volume 72 Issue 11 Pages 2781-2785
Published: November 15, 2003
Released on J-STAGE: July 25, 2007
JOURNAL RESTRICTED ACCESSA turbulent swirling flow is studied with the aid of a variational method. The mean-flow field is expressed by the mean vorticity proportional to its curl. The total axial flux and total helicity per unit length are introduced to characterize the swirling flow, and the condition for the reversal of the axial flow near the center of flow is obtained. On this basis, the helicity injection is discussed in the light of the control of the onset of flow reversal in a turbulent swirling flow. Reference is also made to a cylindrical jet in relation to a swirling laboratory jet and an accretion-disk jet.View full abstractDownload PDF (107K) -
Takeshi Miyazaki, Takahiro Fujiwara, Masahiro Yamamoto2003 Volume 72 Issue 11 Pages 2786-2803
Published: November 15, 2003
Released on J-STAGE: July 25, 2007
JOURNAL RESTRICTED ACCESSA family of exact solutions of the quasigeostrophic equation (in a uniformly stratified fluid on an f-plane) is presented. They are the generalizations of the Meacham–Miyazaki spheroidal vortex to N-confocal tilted prolate spheroids. They rotate steadily in an otherwise quiescent fluid of infinite extent. The angular velocity of rigid rotation is independent of the inclination angle of the axis of symmetry from the vertical axis. The linear instability of double spheroids is investigated by expanding the disturbances in terms of the associated Legendre functions. Three types of instability are found. The first instability seems to be linked with the instability of a highly tilted single slender spheroidal vortex. The second instability, which is observed even for vertically standing spheroids, is caused by resonance between two vortex waves traveling along the inner and outer spheroids. The third instability is the Rayleigh-type instability that occurs for concentric vortex patches with non-monotonic radial vorticity distribution.View full abstractDownload PDF (6146K) -
Evaluation of Ion Temperature Using Ion Sensitive Probe in the Boundary Plasma of the JFT-2M TokamakKazuya Uehara, Ryosuke Fukumoto, Akira Tsushima, Hiroshi Amemiya2003 Volume 72 Issue 11 Pages 2804-2810
Published: November 15, 2003
Released on J-STAGE: July 25, 2007
JOURNAL RESTRICTED ACCESSIn order to extend the capability of the ion sensitive probe (ISP) for the precise measurement of ion temperature, the dependence of the ion current on the height of the electron guard has been evaluated numerically by taking a finite width of the ion collector and the guard into account. It is shown that the ion temperature for strongly magnetized plasma could be experimentally deduced from the current–height characteristics for the ISP more accurately. The ISP technically improved by remote controllable heights has been applied to measure the ion temperature in the ohmically heated and L/H transition plasmas in JFT-2M tokamak.View full abstractDownload PDF (228K) -
Yoshihiro Kuroiwa, Nobufumi Sato, Akikatsu Sawada, Saiko Negishi, Hiro ...2003 Volume 72 Issue 11 Pages 2811-2815
Published: November 15, 2003
Released on J-STAGE: July 25, 2007
JOURNAL RESTRICTED ACCESSThe accurate electron charge density distributions of MoO3 have been investigated by analyzing the synchrotron radiation X-ray powder diffraction data using the MEM (Maximum Entropy Method)/Rietveld method. The covalent bonding is observed only on the five Mo–O bonds, while six O atoms surround the Mo atom. Turning attention to the covalent bonding network, the crystal structure of MoO3 is regarded as a two-dimensional mono-layer structure consisting of the distorted Mo–O5 pyramids. The ionic state of the Mo atom is estimated to be +3.0(1) and those of three O atoms are −1.6(1), −0.7(1), −0.8(1) by counting number of electrons around these atoms, which coincide with the results of theoretical studies.View full abstractDownload PDF (409K) -
R. Kiyanagi, A. Kojima, T. Hayashide, H. Kimura, M. Watanabe, Y. Noda, ...2003 Volume 72 Issue 11 Pages 2816-2821
Published: November 15, 2003
Released on J-STAGE: July 25, 2007
JOURNAL RESTRICTED ACCESSThe hydrogen-bonded material, 5-methyl-9-hydroxyphenalenon (MeHPLN), was studied by X-ray and neutron diffraction experiments at room temperature in order to understand the hydrogen-bond nature and the relation between the hydrogen-bonds and phase transitions. We found that there are obvious discrepancies between the positions of the hydrogen atoms obtained by the X-ray data and the ones obtained by the neutron data. This result indicates that the centers of the electron cloud of the hydrogen atoms are off from the nuclear positions. The discrepancy is markedly seen in the hydrogen atoms participating in the hydrogen-bonds. That is, there are local electronic dipolemoments in the hydrogen-bond region.View full abstractDownload PDF (364K) -
Fuyuki Shimojo, Kozo Hoshino, Y. Zempo2003 Volume 72 Issue 11 Pages 2822-2828
Published: November 15, 2003
Released on J-STAGE: July 25, 2007
JOURNAL RESTRICTED ACCESSThe pressure dependence of the structural and electronic properties of liquid Te is investigated by means of ab initio molecular-dynamics simulations. The anomalous pressure-induced structural change is successfully reproduced by our simulations being in agreement with the observations by the recent synchrotron X-ray-diffraction experiments. Our analyses including the overlap populations reveal that there are two stages in the compression process of the liquid Te. In the first stage under pressure up to about 6 GPa, the elongation of the nearest-neighbor distance is induced by forming a weak covalent bonding state between two Te atoms. In the second stage for further compression, the anisotropy of atomic configuration around each Te atom is reduced with increasing pressure, and the electronic states have a weak pressure dependence.View full abstractDownload PDF (267K) -
Tomoko Kusawake, Ken-ichi Ohshima2003 Volume 72 Issue 11 Pages 2829-2831
Published: November 15, 2003
Released on J-STAGE: July 25, 2007
JOURNAL RESTRICTED ACCESSLow-temperature X-ray intensity measurements have been performed on the development of in-plane and interlayer correlations of the layered compound Cu0.32TiS2. Two types of diffuse scattering, whose maxima appear at 1⁄3,1⁄3,1⁄2 and 2⁄3,2⁄3,1⁄2 (type I) and 1⁄2,0,1⁄2 and 0,1⁄2,1⁄2 (type II), coexist at room temperature. The type I diffuse maxima are gradually increasing with decreasing temperature and becoming constant below 150 K. The full width at half maximum (FWHM) of the intensity profile is almost equal to that of Bragg reflection below 150 K. This means that \\sqrt3×\\sqrt3 R30° ordered structure of intercalated Cu atoms exists. The interlayer correlation length for the structure is about 45 A. On the other hand, weak and broad type II diffuse maxima are less temperature dependent, so that an enhancement of the degree of 2×2 in-plane order is not complete.View full abstractDownload PDF (89K) -
Toshiaki Ohsaka, Yutaka Nigara, Kimihiro Ishi, Yukio Shibata2003 Volume 72 Issue 11 Pages 2832-2836
Published: November 15, 2003
Released on J-STAGE: July 25, 2007
JOURNAL RESTRICTED ACCESSThe far-infrared absorption of pure CeO2, CeO2:CaO and CeO2:ZrO2 solid solutions has been measured at 11 and 297 K in the region 10–100 cm−1. Two apparent absorption peaks are found at 11 K in the vicinity of 50–80 cm−1 only in the CeO2:CaO solid solution with oxygen vacancies, not in the CeO2:ZrO2 solid solution without oxygen vacancies and are assigned to be due to oxygen vacancy modes or attempt modes. The continuous absorption showing a nearly quartic frequency dependence is observed in both the CeO2:CaO and CeO2:ZrO2 solid solutions. This continuous absorption reflects the density of states of acoustic modes and exhibits non-glass-like temperature and frequency dependencies. It is suggested from the above result that the so-called boson peak in glasses does not possess the acoustic mode-like character.View full abstractDownload PDF (153K) -
Yousuke Watanabe, Tetsutaro Masaki, Satoshi Awaji, Kohki Takahashi, Te ...2003 Volume 72 Issue 11 Pages 2837-2842
Published: November 15, 2003
Released on J-STAGE: July 25, 2007
JOURNAL RESTRICTED ACCESSBy utilizing three kinds of incident X-ray radiation under the magnetic fields of 0 T and 5 T, the coexistent region of high-temperature ferromagnetic and low-temperature anti-ferromagnetic phases for the titled manganite oxide was investigated with temperature change between 300 K and 10 K. The unusual extension of the two-phase coexistent region to lower temperature was observed with cooling under 5 T for CuKα radiation, and was estimated due to a surface effect. The large amount of the remnant high-temperature ferromagnetic phase observed in the previous investigations for powder sample under magnetic field was considered by this effect.View full abstractDownload PDF (550K) -
Makoto Iwata, Yoshihiro Ishibashi2003 Volume 72 Issue 11 Pages 2843-2849
Published: November 15, 2003
Released on J-STAGE: July 25, 2007
JOURNAL RESTRICTED ACCESSTemperature dependence of the elastic stiffness constants in Martensite alloys with the symmetry change from the cubic m\\bar3m to the tetragonal 4/mmm and the orthorhombic mmm symmetries was discussed on the basis of the Landau-type free energy function expressed in terms of the strain components, u1, u2 and u3. It was found that an elastic stiffness constant corresponding to the shear deformation, which behaves as a soft mode, becomes extremely small in the vicinity of the transition temperature. The strain–stress hysteresis loops near the transition temperature and the morphotropic phase boundary in the Martensite alloys were also discussed on the basis of the Landau-type free energy function. It was found that the coercive strain field in the stress–strain hysteresis loop decreases with approaching the morphotropic phase boundary, and vanishes there, because there the Landau-type free energy function becomes isotropic in the order parameter space.View full abstractDownload PDF (132K) -
Masahide Sato, Makio Uwaha, Tomonori Mori, Yukio Hirose2003 Volume 72 Issue 11 Pages 2850-2855
Published: November 15, 2003
Released on J-STAGE: July 25, 2007
JOURNAL RESTRICTED ACCESSBy taking account of the alternation of structural parameters, we study bunching of impermeable steps induced by drift of adatoms on a vicinal face of Si(001). With the alternation of diffusion coefficient, the step bunching occurs irrespective of the direction of the drift if the step distance is large. Like the bunching of permeable steps, the type of large terraces is determined by the drift direction. With step-down drift, step bunches grow faster than those with step-up drift. The ratio of the growth rates is as large as the ratio of the diffusion coefficients. Evaporation of adatoms, which does not cause the step bunching, decreases the difference. If only the alternation of kinetic coefficient is taken into account, the step bunching occurs with step-down drift. In an early stage, the initial fluctuation of the step distance determines the type of large terraces, but in a later stage, the type of large terraces is opposite to the case of alternating diffusion coefficient.View full abstractDownload PDF (458K) -
Hideaki Uemura, Yukio Saito, Makio Uwaha2003 Volume 72 Issue 11 Pages 2856-2865
Published: November 15, 2003
Released on J-STAGE: July 25, 2007
JOURNAL RESTRICTED ACCESSThe equilibrium morphology of a two-dimensional (2D) heteroepitaxial adsorbate on a semi-infinite elastic substrate is studied by means of a hybridized method of stress relaxation dynamics in the epitaxial layer and the elastic Green’s function in the substrate. With a small misfit f and a spontaneous surface stress σ0, the epitaxial adsorbate shows a Stranski–Krastanov (SK) configuration with a wetting first layer and islands on further layers. By comparing the results with a rigid substrate, we found that the softness of the substrate turns out to weaken the self-limiting effect of the island size, and the SK islands are found to coarsen indefinitely in the present 2D system.View full abstractDownload PDF (177K) -
Masao Takahashi, Kenn Kubo2003 Volume 72 Issue 11 Pages 2866-2879
Published: November 15, 2003
Released on J-STAGE: July 25, 2007
JOURNAL RESTRICTED ACCESSApplying the dynamical coherent potential approximation to a simple model, we have systematically studied the carrier states in A1−xMnxB-type diluted magnetic semiconductors (DMS’s). The model calculation was performed for three typical cases of DMS’s: cases with strong and moderate exchange interactions in the absence of nonmagnetic potential, and a case with strong attractive nonmagnetic potential in addition to moderate exchange interaction. When the exchange interaction is sufficiently strong, magnetic impurity bands split from the host band. Carriers in the magnetic impurity band mainly stay at magnetic sites, and coupling between the carrier spin and the localized spin is very strong. The hopping of the carriers among the magnetic sites causes ferromagnetism through a double-exchange (DE)-like mechanism. We have investigated the conditions for the operation of DE-like mechanism in DMS’s. The result reveals that the nonmagnetic attractive potential at the magnetic site assists the formation of the magnetic impurity band and makes the DE-like mechanism operative by substantially enhancing the effect of the exchange interaction. Using conventional parameters, we have studied the carrier states in Ga1−xMnxAs. The result shows that the ferromagnetism is caused by the DE-like mechanism via carriers in the band tail originating from the impurity states.View full abstractDownload PDF (408K) -
Masaaki Geshi, Takeo Hoshi, Takeo Fujiwara2003 Volume 72 Issue 11 Pages 2880-2885
Published: November 15, 2003
Released on J-STAGE: July 25, 2007
JOURNAL RESTRICTED ACCESSParallelism of tight-binding molecular dynamics simulations is presented by means of the order-N electronic structure theory with the Wannier states, recently developed [J. Phys. Soc. Jpn. 69 (2000) 3773]. An application is tested for silicon nanocrystals of more than millions atoms with the transferable tight-binding Hamiltonian. The efficiency of parallelism is perfect, 98.8%, and the method is the most suitable to parallel computation. The elapse time for a system of 2×106 atoms is 3.0 min by a computer system of 64 processors of SGI Origin 3800.The calculated results are in good agreement with the results of the exact diagonalization, with an error of 2% for the lattice constant and errors less than 10% for elastic constants.View full abstractDownload PDF (108K) -
Kazuaki Kobayashi, Masao Arai, Kazuo Yamamoto2003 Volume 72 Issue 11 Pages 2886-2892
Published: November 15, 2003
Released on J-STAGE: July 25, 2007
JOURNAL RESTRICTED ACCESSWe calculated the electronic and lattice properties of MgB2 (WB2-type structure), MgB (WC-type structure) and Mg2B2 (Wurtzite-type structure) under hydrostatic and anisotropic (c-axis and a,b-axis) compressions. The lattice properties were optimized automatically by the first-principles molecular dynamics (FPMD) method. The most stable structure is MgB2(AlB2) over a wide range of compression. There is no lattice anomaly for any phase under various compression conditions. The Mg2B2(Wurtzite) phase transforms to a hexagonal-BN (h-BN) type structure (P63/mmc) under c-axis compression.View full abstractDownload PDF (261K) -
Makoto Shirakawa, Hidekazu Aoki, Haruyoshi Aoki, Akira Ochiai2003 Volume 72 Issue 11 Pages 2893-2901
Published: November 15, 2003
Released on J-STAGE: July 25, 2007
JOURNAL RESTRICTED ACCESSTwo kinds of substituted systems, Yb4(As1−xSex)3 and Yb4(As1−xSbx)3, were investigated to clarify the electronic structure of Yb4As3. By the comparison of the magnetic and transport properties of these systems, it is revealed that the Se-substitution causes the decrease of the Yb3+ ions, while the Sb-substitution causes the increase of the holes and the decrease of the Yb3+ ions simultaneously. These results indicate that the number of the holes on the valence p-band almost corresponds to the number of the Yb2+ ions on the one-dimensional magnetic chains in Yb4As3. This scenario could explain many physical properties of the substituted and non-doped Yb4As3.View full abstractDownload PDF (579K) -
Ryoen Shirasaki, Kaoru Iwano2003 Volume 72 Issue 11 Pages 2902-2907
Published: November 15, 2003
Released on J-STAGE: July 25, 2007
JOURNAL RESTRICTED ACCESSOne-dimensional strongly correlated electron system, which is accompanied by interaction with the lattice, has attracted a great deal of interest in both experimental and theoretical studies. At half-filling, this system is a Mott insulator when the electron–lattice interaction is weak. We performed a theoretical investigation of the stable ground state of the one-dimensional strongly correlated electron system with electron–lattice interaction in which one electron is doped from half-filling. We used an extended Peierls–Hubbard model. We report here that, contrary to “common sense” suppositions about the one-dimensional electron–lattice system, a polaron solution appears under conditions of comparatively strong electron–lattice interaction in the Mott phase and that the polaron delocalizes under conditions of weak electron–lattice interaction. These two states are separated by the strength of the electron–lattice interaction.View full abstractDownload PDF (225K) -
Yoshikazu Suzumura, Masato Isobe2003 Volume 72 Issue 11 Pages 2908-2913
Published: November 15, 2003
Released on J-STAGE: July 25, 2007
JOURNAL RESTRICTED ACCESSWe study the effect of impurity pinning on a one-dimensional half-filled electron system, which is expressed in terms of a phase Hamiltonian with the charge degree of freedom. Within the classical treatment, the pinned state is examined numerically. The Mott glass, which has been pointed out by Orignac et al. [Phys. Rev. Lett. 83 (1999) 2378], appears in the intermediate region where the impurity potential competes with the commensurate potential. Such a state is verified by calculating the soliton formation energy, the local restoring force around the pinned state and the optical conductivity.View full abstractDownload PDF (278K) -
Yuki Fuseya, Hiroshi Kohno, Kazumasa Miyake2003 Volume 72 Issue 11 Pages 2914-2923
Published: November 15, 2003
Released on J-STAGE: July 25, 2007
JOURNAL RESTRICTED ACCESSA possibility of the realization of the p-wave spin–singlet superconductivity (pSS), whose gap function is odd both in momentum and in frequency, is investigated by solving the gap equation with the phenomenological interaction mediated by the antiferromagnetic spin fluctuation. The pSS is realized prevailing over the d-wave singlet superconductivity (dSS) in the vicinity of antiferromagnetic quantum critical point (QCP) both on the paramagnetic and on the antiferromagnetic sides. Off the QCP in the paramagnetic phase, however, the dSS with line-nodes is realized as conventional anisotropic superconductivity. For the present pSS state, there is no gap in the quasiparticle spectrum everywhere on the Fermi surface due to its odd frequency. These features can give a qualitative understanding of the anomalous behaviors of NQR relaxation rate on CeCu2Si2 or CeRhIn5 where the antiferromagnetism and superconductivity coexist on a microscopic level.View full abstractDownload PDF (296K) -
Takao Watanabe, Takenori Fujii, Azusa Matsuda2003 Volume 72 Issue 11 Pages 2924-2929
Published: November 15, 2003
Released on J-STAGE: July 25, 2007
JOURNAL RESTRICTED ACCESSFour-circle x-ray diffraction measurements were carried out on a single crystal of Bi2.1Sr1.9Ca2Cu3O10+δ with doping levels from underdoped to overdoped. The excess charge of each inequivalent CuO2 plane was estimated using the obtained inter-atomic distances in two ways by means of the bond–valence-sum method. The copper valence and the valence sum of the copper and the surrounding oxygen ions gave contradictory results for the inhomogeneous charge distribution of the inequivalent CuO2 planes.View full abstractDownload PDF (432K) -
Ryusuke Ikeda2003 Volume 72 Issue 11 Pages 2930-2946
Published: November 15, 2003
Released on J-STAGE: July 25, 2007
JOURNAL RESTRICTED ACCESSMotivated by a mean field-like resistive behavior in magnetic fields commonly seen in various superconducting cuprates and organics with strong fluctuation, superconducting (SC) quantum fluctuation effects on resistive behaviors are reexamined by putting emphasis on their roles in the so-called thermal vortex liquid regime. By incorporating the quantum fluctuations and a vortex pinning effect in the Ginzburg–Landau (GL) fluctuation theory, it is found that the resistivity ρ(T)-curve sharply drops, with no fan-shaped broadening, at a vortex–glass transition point far below an apparent upper critical field Hc2*(T) as a result of a quantum fluctuation enhanced by an adequately small condensation energy or by a strong field. Fittings to ρ–T data of cuprates and organics are performed by phenomenologically including a SC pseudogap region created by high energy SC fluctuations and possible fluctuations of competing non-SC orders. By examining La2−xSrxCuO4 data over a broad doping range, we obtain such conclusions, consistent with recent experimental results, that the in-plane coherence length of hole-doped cuprates decreases with approaching the underdoped limit even in the presence of fluctuating competing orders and that the condensation energy density (Hc(0))2=0.5[φ0⁄(2πλ(0)ξ0)]2 is maximal near the optimal doping. Further, the case of disordered quasi 2D films showing the field-tuned superconductor–insulator transition is also examined for comparison and discussed in relation to data reported recently.View full abstractDownload PDF (288K) -
Shinichiro Kobayashi, Yasuhiro Yoshino, Shigenari Tsuji, Hideki Tou, M ...2003 Volume 72 Issue 11 Pages 2947-2954
Published: November 15, 2003
Released on J-STAGE: July 25, 2007
JOURNAL RESTRICTED ACCESSWe have studied the transport, magnetic and elastic properties of Ce0.8La0.2B6 single crystal. The phase IV which existed for x≤0.75 in CexLa1−xB6 was found to exist in this sample but its existence region is very small. The magnetic phase diagram indicates that the phase IV appears in order to avoid a direct contact between the antiferromagnetic phase III dominated by the Oxy-type antiferro-quadrupolar ordering and the paramagnetic phase I. The anisotropy of the magnetization was discovered in the phase IV above H∼0.3 T. There, the magnetization is large for H||⟨001⟩ but small for H||⟨110⟩. From the results of the anisotropic behaviors of the magnetization in the phase IV, we proposed that there exist the three domain states, Kxy, Kyz and Kzx at H=0 and in the Kxy domain, M under H||z is large and that under H||x or y is small. Based on the anisotropy of M and the smooth x dependence of TN and TNIV–I through x∼0.8, we discussed the possibility of the magnetic ordering in the phase IV. Tβ-type antiferro-octupolar ordering whose possibility was discussed in detail by Kuramoto and Kusunose [J. Phys. Soc. Jpn. 69 (2000) 671] is also discussed.View full abstractDownload PDF (288K) -
Ryosuke Kadono, Kazuki Ohishi, Akihiro Koda, Wataru Higemoto, Kenji M. ...2003 Volume 72 Issue 11 Pages 2955-2958
Published: November 15, 2003
Released on J-STAGE: July 25, 2007
JOURNAL RESTRICTED ACCESSThe magnetic ground state of an electron-doped cuprate superconductor, Pr1−xLaCexCuO4+α−δ (x=0.11, α\\simeq0.04), has been studied by means of muon spin rotation/relaxation (μSR) over a wide variety of oxygen depletion, 0.03≤δ≤0.12. The appearance of a weak random magnetism over the entire crystal volume has been revealed by a slow exponential relaxation. The absence of δ-dependence for random magnetism and a multiplet pattern of the muon Knight shift at higher fields strongly suggest that the random moments are associated with excited Pr3+ ions under a crystal electric field.View full abstractDownload PDF (171K) -
Eiichi Hanamura, Yukito Tanabe2003 Volume 72 Issue 11 Pages 2959-2966
Published: November 15, 2003
Released on J-STAGE: July 25, 2007
JOURNAL RESTRICTED ACCESSIt has been experimentally confirmed that the ferroelectric (FEL) and antiferromagnetic (AFM) order-parameter in hexagonal YMnO3 are coupled at the FEL domain boundary. A microscopic model for this clamping of the two order-parameters is proposed. The clamping can be understood as due to the change of exchange integrals induced by the spin–orbit interaction and low symmetry field within the FEL domain boundary and due to spin anisotropy energy which depends on the sign of FEL polarization.View full abstractDownload PDF (169K) -
Jiang Cai, Yoshifumi Harada, Meiro Chiba, Takayuki Hirata2003 Volume 72 Issue 11 Pages 2967-2971
Published: November 15, 2003
Released on J-STAGE: July 25, 2007
JOURNAL RESTRICTED ACCESSIntermittent behavior in magnon systems is studied through ferromagnetic resonance experiments using a sphere of yttrium–iron–garnet (YIG) under X-band microwave pumping. Intermittency is observed near the microwave power of the onset of the second-order Suhl instability. Based on Kullback–Leibler information theory we considered two models of the laminar length distribution: an exponential model and a power law model. At low power, the distribution follows an exponential model, indicating a predominantly Poisson process, transitioning to a power law model at higher power, indicating chaotic dynamics. This transition suggests that an orderly state arises due to magnon–magnon interaction from the initially disordered state (random process) with increasing microwave power.View full abstractDownload PDF (189K) -
K.-H. Chew, Y. Ishibashi, F. G. Shin, H. L. W. Chan2003 Volume 72 Issue 11 Pages 2972-2978
Published: November 15, 2003
Released on J-STAGE: July 25, 2007
JOURNAL RESTRICTED ACCESSA generalized thermodynamic theory (effective Landau–Devonshire-type theory) for ferroelectric thin films undergoing second order phase transition is developed within the framework of the Landau–Ginzburg theory via the concept of extrapolation length δ in the Tilley–Zeks model. The free energy of the Tilley–Zeks model for ferroelectric thin films is cast into a clearer and simpler form from the usual integral expression form using suitable order parameters. The target coefficients A and B for the second order and fourth order terms, respectively, of the free energy are expressed as a function of temperature, film thickness, extrapolation length and other physical parameters. The intrinsic effects of surface on the order of phase transitions are discussed analytically with an emphasis on asymmetric films.View full abstractDownload PDF (110K) -
Mitsuo Machida2003 Volume 72 Issue 11 Pages 2979-2983
Published: November 15, 2003
Released on J-STAGE: July 25, 2007
JOURNAL RESTRICTED ACCESSThe ferroelectric transition in the monoclinic K2ZnBr4 was studied by the molecular dynamics (MD) simulation. Wave-vector dependence of the mode-coupling constant along the c* axis is determined in the paraelectric phase for the transverse optic (TO) and librational (TL) modes which have the Au- and Bg-symmetries at the zone center, respectively. The coupling constant takes a maximum at the zone center, showing that there exists strong correlation between the Au and Bg modes. Dispersion relations of the TO and TL modes are determined along the c* axis in the paraelectric phase. The frequency of the TO mode decreases toward the zone center from the zone boundary. The TL mode shows also a similar behavior but the dispersion is very small compared to the TO mode. The Bg mode keeps its frequency almost invariant over the both paraelectric and ferroelectric phases. In contrast, the frequency of the Au mode decreases fairly as temperature approaches the transition point.View full abstractDownload PDF (194K) -
Akira Shojiguchi, Kiyoshi Kobayashi, Suguru Sangu, Kazuo Kitahara, Mot ...2003 Volume 72 Issue 11 Pages 2984-3001
Published: November 15, 2003
Released on J-STAGE: July 25, 2007
JOURNAL RESTRICTED ACCESSA model is presented for a system of N two-level excitons interacting with each other via optical near fields represented as localized photons. In a low exciton density limit, quantum dynamics of the dipole moments or quantum coherence between any two energy levels is linear. As the exciton density becomes higher, the dynamics becomes nonlinear, and the system has several kinds of quasi-steady states of the dipole distribution depending on the system parameters. These quasi-steady states are classified with the help of the effective Hamiltonian that is derived from the renormalization of degrees of freedom of localized photons with a unitary transformation. Among them there exist a “ferromagnetic” state (dipole-ordered state), in which all electric dipoles are aligned in the same direction, and an “anti-ferromagnetic” state, where all dipoles alternatingly change the direction. In addition, we show that an arbitrary state can be transformed into a dipole-ordered state by manipulating initial values of the population differences appropriately. For example, if we initially prepare a dipole-forbidden state, which is similar to the “anti-ferromagnetic” state and cannot be coupled with propagating far fields, and if we manipulate the distribution of the population differences properly, the initial state evolves into a dipole-ordered state. The radiation property of such dipole-ordered states is examined in detail. Neglecting energy dissipation by radiation, we find that some of the ordered states show strong radiation equivalent to Dicke’s superradiance. Then by introducing a radiation reservoir, the dissipative master equation is derived. Solving the equation with and without quantum correlations, we numerically show that multiple peaks in the radiation profile can survive in both cases. The mechanism of this phenomenon is discussed, and a brief comment on an application to photonic devices on a nanometer scale is given.View full abstractDownload PDF (1085K) -
Koji Matsumura, Y-h. Taguchi2003 Volume 72 Issue 11 Pages 3002-3005
Published: November 15, 2003
Released on J-STAGE: July 25, 2007
JOURNAL RESTRICTED ACCESSWe have developed a toy model of flying snake’s glide [J. J. Socha: Nature 418 (2002) 603] by modifying a model for a falling paper. We have found that asymmetric oscillation is a key about why snake can glide. Further investigation for snake’s glide will provide us details about how it can glide without a wing.View full abstractDownload PDF (133K) -
Imad A. Barghouthi, Elias I. Elias, Mahmoud A. Abu Samra, Naji A. Qata ...2003 Volume 72 Issue 11 Pages 3006-3013
Published: November 15, 2003
Released on J-STAGE: July 25, 2007
JOURNAL RESTRICTED ACCESSAltitude profiles for O+ ion velocity distribution functions, O+ parallel and perpendicular temperatures, O+ temperature anisotropy, O+–O+ and O+–O collision frequencies and O+ temperature partition coefficients β|| and β⊥ are obtained in the auroral ionosphere (150 km–500 km). A Monte Carlo simulation was used to investigate the behavior of O+ ions that are E×B drifting through a background of neutrals O, with the effects of O+–O resonant charge exchange and polarization interactions as well as O+–O+ Coulomb collisions. We have found, for low altitudes, the effect of O+–O+ Coulomb collisions is negligible and, as electric field increases, O+–O collision rate increases, therefore non-Maxwellian features of fO+ appeared and becomes pronounced at large electric fields, O+ temperature increases, νO+–O increases, νO+–O+ decreases, O+ temperature partition coefficients β|| decreases and β⊥ increases. As altitude increases, the effect of O+–O+ Coulomb collision becomes significant, and for constant electric field, the non-Maxwellian features of O+ distributions are reduced, T⊥O+ decreases, T||O+ increases, O+ temperature anisotropy decreases, νO+–O decreases, νO+–O+ increases with altitude and reaches its maximum at 300 km and then decreases, β|| increases and β⊥ decreases. However, as E increases, the O+–O collision frequency increases, while O+–O+ collision frequency decreases, β|| decreases, β⊥ increases, νO+–O increases, νO+–O+ decreases. Monte Carlo simulation of the effect of O+–O+ Coulomb collision on the O+ temperature partition coefficients β|| and β⊥, which has not been taken into account so far, is to increase β|| and decreases β⊥. We believe that the Monte Carlo calculations presented here provided the best description to date of auroral F-region O+ velocity distributions, O+ temperature and O+ temperature partition coefficients β|| and β⊥ in the presence of the electric field, primarily because of the self consistent handling of O+–O+ and O+–O collisions.View full abstractDownload PDF (181K) -
Yukio Yasui, Minoru Soda, Satoshi Iikubo, Masafumi Ito, Masatoshi Sato ...2003 Volume 72 Issue 11 Pages 3014-3015
Published: November 15, 2003
Released on J-STAGE: July 25, 2007
JOURNAL RESTRICTED ACCESSDownload PDF (226K)
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