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Volume 75, Issue 6
Displaying 1-46 of 46 articles from this issue
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Hidetsugu Sakaguchi2006 Volume 75 Issue 6 Pages 063001
Published: June 15, 2006
Released on J-STAGE: August 27, 2009
JOURNAL RESTRICTED ACCESSA simple tight-coupling model of a molecular chemical engine is proposed. The efficiency of the chemical engine and its average velocity can be explicitly calculated. The diffusion constant is evaluated approximately using the fluctuation theorem. Langevin simulations with stochastic boundary conditions are performed and the numerical results are compared with theoretical calculations.View full abstractDownload PDF (131K) -
Hiromitsu Takeuchi, Makoto Tsubota2006 Volume 75 Issue 6 Pages 063601
Published: June 15, 2006
Released on J-STAGE: August 27, 2009
JOURNAL RESTRICTED ACCESSA boojum is a topological defect that can form only on the surface of an ordered medium such as superfluid 3He and liquid crystals. We study theoretically boojums appearing between two phases with different vortex structures in two-component BECs where the intracomponent interaction is repulsive in one phase and attractive in the other. The detailed structure of the boojums is revealed by investigating its density distribution, effective superflow vorticity and pseudospin texture.View full abstractDownload PDF (718K) -
C. Michioka, H. Ohta, Y. Itoh, K. Yoshimura2006 Volume 75 Issue 6 Pages 063701
Published: June 15, 2006
Released on J-STAGE: August 27, 2009
JOURNAL RESTRICTED ACCESSWe report 59Co nuclear quadrupole resonance (NQR) studies of bilayer water intercalated sodium cobalt oxides NaxCoO2·yH2O (BLH) with the superconducting transition temperatures, 2K<Tc≤4.6K, as well as a magnetic BLH sample without superconductivity. We obtained a magnetic phase diagram of Tc and the magnetic ordering temperature TM against the peak frequency ν3 of the 59Co NQR transition Iz=±5⁄2↔±7⁄2 and found a dome-shaped superconducting phase. The 59Co NQR spectrum of the nonsuperconducting BLH shows a broadening below TM without the critical divergence of 1⁄T1 or 1⁄T2, suggesting an unconventional magnetic ordering. The degree of enhancement of 1⁄T1T at low temperatures increases with the increase of ν3 though the optimal ν3 of approximately 12.30 MHz. In the NaxCoO2·yH2O system, the optimal-Tc superconductivity emerges close to the magnetic instability. Tc is suppressed near the phase boundary at ν3∼12.50 MHz, which is not a conventional magnetic quantum critical point.View full abstractDownload PDF (144K) -
Hiroshi Watanabe, Masao Ogata2006 Volume 75 Issue 6 Pages 063702
Published: June 15, 2006
Released on J-STAGE: August 27, 2009
JOURNAL RESTRICTED ACCESSMotivated by the various physical properties observed in θ-(BEDT-TTF)2X, we study the ground state of an extended Hubbard model on two-dimensional anisotropic triangular lattice at 1/4-filling with the variational Monte Carlo method. It is shown that the nearest-neighbor Coulomb interaction enhances charge fluctuation and it induces anomalous states such as the charge-ordered metallic state and triplet next-nearest-neighbor f-wave superconductivity. We consider that these results can explain the coexistence of different charge orders observed in the case of X = CsCo(SCN)4 and superconductivity in the case of X = I3. We then propose a unified view of the family of organic conductors θ-(BEDT-TTF)2X with the value of tc⁄tp.View full abstractDownload PDF (151K) -
Aya Yamamoto, Shinji Wada, Ichimin Shirotani, Chihiro Sekine2006 Volume 75 Issue 6 Pages 063703
Published: June 15, 2006
Released on J-STAGE: August 27, 2009
JOURNAL RESTRICTED ACCESSWe have carried out 31P-NMR study on a new intermediate-valence compound YbFe4P12 with a filled skutterudite structure which has heavy fermion-like properties below ∼10 K. The Knight shift has a very small value less than 0.05%, and the linewidth exhibits a monotonic increase without exhibiting any singular behavior down to 0.5 K. The nuclear spin–lattice relaxation rate 1⁄T1T below ∼50 K strongly depends on both the temperature T and applied magnetic field H and follows the power-law relation 1⁄T1T=AT−α over one decade. The power α∼0.1 at 7.0 T increases with decreasing H and takes the maximum value of \\simeq0.7 at 0.2 T, which is close to the value 3/4 expected for the non-Fermi liquid (NFL) state associated with antiferromagnetic spin fluctuations. We suggest that YbFe4P12 is an interesting material in which the NFL-like behavior occurs below a rather high temperature of ∼10 K, and a magnetic field of about 0.2 T is sufficient to bring it to its quantum critical point.View full abstractDownload PDF (240K) -
Manabu Machida, Naomichi Hatano, Jun Goryo2006 Volume 75 Issue 6 Pages 063704
Published: June 15, 2006
Released on J-STAGE: August 27, 2009
JOURNAL RESTRICTED ACCESSWe study a nonadiabatic effect on the conductances in the quantum Hall effect of two-dimensional electrons with a periodic potential. We found that the Hall and longitudinal conductances oscillate in time with very large frequencies due to quantum fluctuation.View full abstractDownload PDF (312K) -
Kazuki Ohishi, Wataru Higemoto, Akihiro Koda, Shanta R. Saha, Ryosuke ...2006 Volume 75 Issue 6 Pages 063705
Published: June 15, 2006
Released on J-STAGE: August 27, 2009
JOURNAL RESTRICTED ACCESSLocal magnetic fields in a molecule-based optically chiral magnet [Cr(CN)6][Mn(S)-pnH(H2O)](H2O) [GN-(S)] and its enantiomer [GN-(R)] were studied by means of muon spin rotation and relaxation (μSR). A detailed analysis of μSR signals under a zero field observed in the magnetically ordered state supports the average magnetic structure suggested by the result of neutron powder diffraction. Moreover, a comparison of μSR spectra between GN-(S) and GN-(R) suggests that they are a pair of complete optical isomers in terms of both crystallographic and magnetic structures. The possibility of magnetic chirality in such a pair is discussed.View full abstractDownload PDF (533K) -
Hideo Yoshioka, Masahisa Tsuchiizu, Hitoshi Seo2006 Volume 75 Issue 6 Pages 063706
Published: June 15, 2006
Released on J-STAGE: August 27, 2009
JOURNAL RESTRICTED ACCESSFinite-temperature charge-ordering phase transition in quasi one-dimensional (1D) molecular conductors is investigated theoretically, based on a quasi 1D extended Hubbard model at quarter filling with interchain Coulomb repulsion V⊥. The interchain term is treated within a mean-field approximation, and the 1D fluctuations in the chains are fully taken into account by the bosonization theory. Three regions are found depending on the appearance of the charge-ordered state at a finite temperature when V⊥ is introduced: (i) a weak-coupling region where the system transforms from a metal to a charge-ordered insulator with a finite transition temperature at a finite critical value of V⊥, (ii) an intermediate region where this transition occurs by infinitesimal V⊥ due to the stability of the inherent 1D fluctuation, and (iii) a strong-coupling region where the charge ordered state is already realized in a purely 1D case, of which the transition temperature becomes finite with infinitesimal V⊥. An analytical formula for the V⊥ dependence of the transition temperature is derived for each region.View full abstractDownload PDF (116K) -
Gyong Luck Khym, Youngnae Lee, Kicheon Kang2006 Volume 75 Issue 6 Pages 063707
Published: June 15, 2006
Released on J-STAGE: August 27, 2009
JOURNAL RESTRICTED ACCESSWe study the charge detection and controlled dephasing of a mesoscopic system via a quantum dot detector (QDD), in which the mesoscopic system and the QDD are capacitively coupled. The QDD is considered to exhibit coherent resonant tunnelling via a single level. It is found that dephasing rate is proportional to the square of the conductance of the QDD for the Breit–Wigner model, showing that dephasing is completely different from the shot noise of the detector. Measurement rate, on the other hand, shows a dip near the resonance of the QDD. Our findings are unique especially for a symmetric detector in the following aspects: The dephasing rate is maximum at the resonance of the QDD in which detector conductance is insensitive to the charge state of the mesoscopic system. As a result, the efficiency of the detector shows a dip and vanishes at the resonance, in contrast to the single-channel symmetric nonresonant detector that always has a maximum efficiency. We find that this difference originates from a very general property of the scattering matrix: An abrupt phase change exists at scattering amplitude in the presence of the symmetry, which is insensitive to detector current but stores information on the quantum state of a mesoscopic system.View full abstractDownload PDF (225K) -
Koyo Tamura, Rinto Anugraha, Ryohei Matsuo, Yoshiki Hidaka, Shoichi Ka ...2006 Volume 75 Issue 6 Pages 063801
Published: June 15, 2006
Released on J-STAGE: August 27, 2009
JOURNAL RESTRICTED ACCESSSoft-mode turbulence (SMT) is a spatiotemporal chaos in electrohydrodynamic convective systems. It is caused by a nonlinear interaction between the convection mode and a Nambu–Goldstone mode, and bifurcates supercritically from a stationary uniform state. In this paper, we clarify that a spatial structure larger than a convective roll exists in SMT, which shows a patchlike domain structure characterized by wavevector directions. The dependence of the average size of the patch structure on the control parameter ε is given as ε−1⁄2.View full abstractDownload PDF (170K) -
Hiroshi Orihara, Tetsunori Shibuya, Tomoyuki Nagaya, Seiji Ujiie2006 Volume 75 Issue 6 Pages 063802
Published: June 15, 2006
Released on J-STAGE: August 27, 2009
JOURNAL RESTRICTED ACCESSThe morphology and rheology of an immiscible polymer blend under electric and shear flow fields were studied. A transition from a droplet-dispersed structure to a network structure was observed by using a specially designed shearing device and a confocal scanning laser microscope. This was accompanied by a change in viscosity. By digitally processing captured serial images in steady states at different shear rates and electric fields, we found scaling properties.View full abstractDownload PDF (344K) -
Tetsu Yajima, Keisuke Nakajima, Naruyoshi Asano2006 Volume 75 Issue 6 Pages 064001
Published: June 15, 2006
Released on J-STAGE: August 27, 2009
JOURNAL RESTRICTED ACCESSA generalization of the max-plus transformation, which is known as a method to derive cellular automata from integrable equations, is proposed for complex variables. Operation rules for this transformation is also studied for general number of variables. As an application, the max-plus transformation is applied to the discrete Fourier transformation. Ultradiscretized wave equation and nonlinear Schrödinger equation are solved by the proposed method. The solution has discrete values with inner structures in a discrete space and time.View full abstractDownload PDF (187K) -
Masaru Uchiyama, Jun’ichi Ieda, Miki Wadati2006 Volume 75 Issue 6 Pages 064002
Published: June 15, 2006
Released on J-STAGE: August 27, 2009
JOURNAL RESTRICTED ACCESSWe study dark soliton solutions of a multi-component Gross–Pitaevskii equation for hyperfine spin F=1 spinor Bose–Einstein condensate. The interactions are supposed to be inter-atomic repulsive and anti-ferromagnetic ones of equal magnitude. The solutions are obtained from those of an integrable 2×2 matrix nonlinear Schrödinger equation with nonvanishing boundary conditions. We investigate the one-soliton and two-soliton solutions in detail. One-soliton is classified into two kinds. The ferromagnetic state has wavefunctions of domain-wall shape and its total spin is nonzero. The polar state provides a hole soliton and its total spin is zero. These two states are selected by choosing the type of the boundary conditions. In two-soliton collisions, we observe the spin-mixing or spin-transfer. It is found that, as “magnetic” carriers, solitons in the ferromagnetic state are operative for the spin-mixing while those in the polar are passive.View full abstractDownload PDF (325K) -
Yoshihito Ogasawara, Akihiko Kitada2006 Volume 75 Issue 6 Pages 064003
Published: June 15, 2006
Released on J-STAGE: August 27, 2009
JOURNAL RESTRICTED ACCESSThe evolution equation of an interface based on a mass transfer and that based on a heat transfer are unified into a nonlinear evolution equation for two spatial variables, and the properties of the solution of this equation are discussed without employing any linear approximations. Then, through these discussions, the intrinsic conditions which characterize the morphological stability are exhibited.View full abstractDownload PDF (392K) -
Shu-Qiang Lü, Xing-Biao Hu, Q. P. Liu2006 Volume 75 Issue 6 Pages 064004
Published: June 15, 2006
Released on J-STAGE: August 27, 2009
JOURNAL RESTRICTED ACCESSIn this paper, we propose a supersymmetric Ito equation (sIto) and calculate its one-, two-, and three-soliton solutions within the framework of Hirota’s bilinear method. We also construct the Lax representation, Bäcklund transformation and nonlinear superposition formula for this supersymmetric equation.View full abstractDownload PDF (104K) -
Hidekazu Tokuda, Takao Ohta2006 Volume 75 Issue 6 Pages 064005
Published: June 15, 2006
Released on J-STAGE: August 27, 2009
JOURNAL RESTRICTED ACCESSWe study dynamics of traveling waves under spatio-temporal external forcing in non-equilibrium open systems. We employ the model system where phase separation and chemical reactions take place simultaneously so that traveling waves are formed in a self-organized manner. Entrainment and modulation of traveling waves under space-time dependent external forcing are investigated numerically in one dimension. In particular, we focus our attention on the case that the spatial period of the external forcing is different from the intrinsic period of the traveling waves. A conjecture is given about the mode selection of the nonlinear waves.View full abstractDownload PDF (358K) -
Minoru Ogawa2006 Volume 75 Issue 6 Pages 064006
Published: June 15, 2006
Released on J-STAGE: August 27, 2009
JOURNAL RESTRICTED ACCESSIn this paper, we treat symplectic difference equations with one degree of freedom. For such cases, we see that the relationship between that the dynamics on the two-dimensional phase space is reduced to be on one-dimensional level sets by a conserved quantity and that the dynamics is integrable, under some assumptions. The process which we introduce is related to interval exchange transformations.View full abstractDownload PDF (110K) -
Kiyoshi Sogo2006 Volume 75 Issue 6 Pages 064007
Published: June 15, 2006
Released on J-STAGE: August 27, 2009
JOURNAL RESTRICTED ACCESSA discrete version of Euler’s Elastica problem is formulated by a variational principle. Hirota’s bilinear equations, Lax pair formalism and the exact solution are obtained explicitly. Geometrical properties are also discussed such as discrete Frenet–Serret equations.View full abstractDownload PDF (91K) -
K. Fushimi, H. Kawasuso, E. Aihara, R. Hayami, M. Toi, K. Yasuda, S. N ...2006 Volume 75 Issue 6 Pages 064201
Published: June 15, 2006
Released on J-STAGE: August 27, 2009
JOURNAL RESTRICTED ACCESSA thin (0.05 cm) and wide area (5×5 cm2) NaI(Tl) scintillator was developed. The performance of the thin NaI(Tl) plate, energy resolution, single photoelectron energy and position sensitivity were tested. An excellent energy resolution of 20% (FWHM) at 60 keV was obtained. The single photoelectron energy was calculated to be approximately 0.42±0.02 keV. Position information in the 5×5 cm2 area of the detector was also obtained by analyzing the ratio of the number of photons collected at opposite ends of the detector. The position resolution was obtained to be 1 cm (FWHM) in the 5×5 cm2 area.View full abstractDownload PDF (343K) -
K. Fujimura2006 Volume 75 Issue 6 Pages 064401
Published: June 15, 2006
Released on J-STAGE: August 27, 2009
JOURNAL RESTRICTED ACCESSNumerical simulation has been carried out on the evolution of two-dimensional disturbances in plane Poiseuille flow. In a linearly stable region, we introduced a single anti-symmetric eigenmode belonging to the Orr–Sommerfeld spectra, and examined whether or not Tollmien–Schlichting waves were excited beyond a threshold of the subcritical instability. It is shown that a wall mode may easily trigger the nonlinear growth beyond the threshold. An initial threshold amplitude, above which the subcritical instability eventually sets in, depends on the initially introduced eigenmode: both the fifth and the eighth eigenmodes have the initial thresholds about ten times larger than that of the first eigenmode. Except for the initially introduced one, for t≤1, all the eigencomponents embedded in the fundamental Fourier mode are found to exhibit transient growth of ∝t2. It is due to the nonlinear self-interaction of the initial disturbance.View full abstractDownload PDF (937K) -
T. Chonan, S. Katayama2006 Volume 75 Issue 6 Pages 064601
Published: June 15, 2006
Released on J-STAGE: August 27, 2009
JOURNAL RESTRICTED ACCESSMolecular-dynamics studies on lattice thermal conductivity (κL) of Pb1−xSnxTe and Pb1−xGexTe are carried out by employing ion model potential for mutual ion-ion interactions at the average temperatures 300 and 500 K under non-equilibrium condition. Special emphasis of investigation is placed on the alloying effects of κL calculated by changing the alloy content x in PbTe-based alloys. It has been shown that a remarkable reduction of κL at finite x is demonstrated in Pb1−xSnxTe and Pb1−xGexTe without relying on a phonon scattering description. We have compared our results with ones evaluated by the Abeles’ formula of lattice thermal conductivity due to phonon scattering from alloy fluctuations.View full abstractDownload PDF (265K) -
MD Calculation Studies of Residence Site and Diffusion Path of Li Ions in Perovskite-Type (LaLi)TiO3Yasuaki Maruyama, Hiroaki Ogawa, Makoto Kamimura, Michisuke Kobayashi2006 Volume 75 Issue 6 Pages 064602
Published: June 15, 2006
Released on J-STAGE: August 27, 2009
JOURNAL RESTRICTED ACCESSA computer simulation is performed by a molecular dynamics method to study the structural and dynamical properties in superionic conductor La4⁄3−xLi3x\\square2⁄3−2xTi2O6 (\\square=vacancy), which is the perovskite-type Li ion conductor. At low Li concentrations, Li ions conduct with a two-dimensional motion, while Li ions diffuse with a three-dimensional motion at high Li ion concentrations. The partial distribution function for Li–Ti and the diffusion paths of Li ions suggest that Li ions stay for a long time at off-site positions which are 2.7 Å away from a body-centered Ti ion. The Li ion concentration dependence of σ is in approximate agreement with experiments.View full abstractDownload PDF (1367K) -
Hiroko Kaji, Kiminori Kakitani, Akio Yoshimori2006 Volume 75 Issue 6 Pages 064603
Published: June 15, 2006
Released on J-STAGE: August 27, 2009
JOURNAL RESTRICTED ACCESSThe electronic states of the clean Si(100)2×1 surface disordered system are calculated at various temperatures using the Monte Carlo simulation technique. The calculation generates the position of the atoms based on the Ising model and gives numerically the electronic eigenstates based on the tight-binding model on each generated disordered structure. The electronic structure is discussed in terms of the density of states projected to the reciprocal space averaged over those obtained electronic states. The results clarify that the short-range ordering effect is the origin of the behavior found in experiments.View full abstractDownload PDF (1070K) -
Shafiq Ahmad, M. Ayaz Ahmad, M. Irfan, M. Zafar2006 Volume 75 Issue 6 Pages 064604
Published: June 15, 2006
Released on J-STAGE: August 27, 2009
JOURNAL RESTRICTED ACCESSAn attempt is made to study the existence of non-statistical fluctuations of relativistic particles using the method of scaled factorial moments (SFMs) in the interactions of 28Si and 12C nuclei at 4.5 A GeV/c with nuclear emulsion. The experimental result has also been compared with FRITIOF generated data. The analysis of SFMs gives an evidence for an intermittency pattern of fluctuations. The increasing trend of anomalous fractal dimensions, dq, of the pseudo-rapidity distribution with the order of the moment, q observed in the present study supports a self-similar cascade mechanism. The results for experimental data are quite consistent with those obtained for FRITIOF data. Finally, it can be concluded that no universality in the values of the multifractal specific, c, is found for our data.View full abstractDownload PDF (252K) -
Sadayoshi Kanamaru, Hidekatsu Suzuura, Hiroshi Akera2006 Volume 75 Issue 6 Pages 064701
Published: June 15, 2006
Released on J-STAGE: August 27, 2009
JOURNAL RESTRICTED ACCESSSpatial distributions of the electron temperature perpendicular to the applied current are obtained in quantum Hall systems with compressible and incompressible strips at low lattice temperatures by solving equations of electron number conservation and energy conservation as well as Poisson’s equation self-consistently. In the linear-response regime, variations of the electron temperature concentrate in the incompressible strips as the lattice temperature decreases. The electron temperature indicates an anti-symmetric distribution: it becomes lower than the lattice temperature in the side of a sample with a higher electrochemical potential, and higher in the opposite side. Around the breakdown of the quantum Hall effects, the electron temperature becomes much higher than the lattice temperature as the applied current increases. Reflecting the anti-symmetric distribution in the linear-response regime, the rise of the electron temperature is suppressed in the higher potential side with increasing current. In the same side, the current density becomes large and the current-induced potential shows a steep variation. At even larger currents, accompanying disappearance of the compressible and incompressible strips, the electron temperature becomes uniform.View full abstractDownload PDF (772K) -
Yoshiko Obiraki, Hiroshi Nakashima, Andrei Galatanu, Tatsuma D Matsuda ...2006 Volume 75 Issue 6 Pages 064702
Published: June 15, 2006
Released on J-STAGE: August 27, 2009
JOURNAL RESTRICTED ACCESSWe succeeded in growing single crystals of ferromagnets NdRh3B2 and GdRh3B2 with the hexagonal structure, and measured the electrical resistivity, specific heat, magnetic susceptibility and magnetization. From these measurements, the Curie temperature TC is determined as TC=10.2 K in NdRh3B2 and TC=93 K in GdRh3B2. The magnetic moments of about 2.5 μB in NdRh3B2 and 7.7 μB in GdRh3B2 are oriented in the basal plane. The crystalline electric field scheme is proposed for NdRh3B2 on the basis of the experimental results of Schottky anomaly in the specific heat and anisotropic susceptibility and magnetization. The Fermi surface in NdRh3B2 is very similar to that in a non-4f reference compound LaRh3B2, possessing the quasi-one dimensional electronic character.View full abstractDownload PDF (1457K) -
Kenji Goto, Masashi Fujisawa, Hidekazu Tanaka, Yoshiya Uwatoko, Akira ...2006 Volume 75 Issue 6 Pages 064703
Published: June 15, 2006
Released on J-STAGE: August 27, 2009
JOURNAL RESTRICTED ACCESSMagnetization and neutron elastic scattering measurements under a hydrostatic pressure were performed on KCuCl3, which is a three-dimensionally coupled spin dimer system with a gapped ground state. It was found that an intradimer interaction decreases with increasing pressure, while the sum of interdimer interactions increases. This leads to the shrinkage of spin gap. A quantum phase transition from a gapped state to an antiferromagnetic state occurs at Pc≈8.2 kbar. For P>Pc, magnetic Bragg reflections were observed at reciprocal lattice points equivalent to those for the lowest magnetic excitation at zero pressure. This confirms that the spin gap decreases and closes under applied pressure.View full abstractDownload PDF (302K) -
Moo-Sung Kim, Yuki Nakai, Hideki Tou, Masafumi Sera, Fumitoshi Iga, To ...2006 Volume 75 Issue 6 Pages 064704
Published: June 15, 2006
Released on J-STAGE: August 27, 2009
JOURNAL RESTRICTED ACCESSThe thermopower, S, of CexR1−xB6 (R=La, Pr, Nd) was investigated. S with a positive sign shows a typical behavior observed in the Ce Kondo system, an increase with decreasing temperature at high temperatures and a maximum at low temperatures. The S values of all the systems at high temperatures are roughly linearly dependent on the Ce concentration, indicating the conservation of the single-impurity character of the Kondo effect in a wide x range. However, the maximum value of S, Smax, and the temperature, Tmax, at which Smax is observed exhibit different x dependences between CexLa1−xB6 and CexR1−xB6 (R=Pr, Nd). In CexLa1−xB6, Tmax, which is ∼8 K in CeB6, decreases with decreasing x and converges to ∼1 K in a very dilute alloy and Smax shows an increase below x∼0.1 after decreasing with decreasing x. In CexR1−xB6 (R=Pr, Nd), Tmax shows a weak x dependence but Smax shows a roughly linear decrease in x. These results are discussed from the standpoint of the chemical pressure effect and the Ce–Ce interaction. S in the long-range ordered phase shows very different behaviors between CexPr1−xB6 and CexNd1−xB6.View full abstractDownload PDF (540K) -
Takahiro Misawa, Youhei Yamaji, Masatoshi Imada2006 Volume 75 Issue 6 Pages 064705
Published: June 15, 2006
Released on J-STAGE: August 27, 2009
JOURNAL RESTRICTED ACCESSTricritical point in charge-order systems and its criticality are studied for a microscopic model by using the mean-field approximation and exchange Monte Carlo method in the classical limit as well as by using the Hartree–Fock approximation for the quantum model. We study the extended Hubbard model and show that the tricritical point emerges as an endpoint of the first-order transition line between the disordered phase and the charge-ordered phase at finite temperatures. Strong divergences of several fluctuations at zero wavenumber are found and analyzed around the tricritical point. Especially, the charge susceptibility χc and the susceptibility of the next-nearest-neighbor correlation χR are shown to diverge and their critical exponents are derived to be the same as the criticality of the susceptibility of the double occupancy χD(0). The singularity of conductivity at the tricritical point is clarified. We show that the singularity of the conductivity σ is governed by that of the carrier density and is given as |σ−σc|∼|g−gc|pt(Alog|g−gc|+B), where g is the effective interaction of the Hubbard model, σc (gc) represents the critical conductivity(interaction) and A and B are constants, respectively. Here, in the canonical ensemble, we obtain pt=2βt=1⁄2 at the tricritical point. We also show that pt changes into pt′=2β=1 at the tricritical point in the grand-canonical ensemble when the tricritical point in the canonical ensemble is involved within the phase separation region. The results are compared with available experimental results of organic conductor (DI-DCNQI)2Ag.View full abstractDownload PDF (904K) -
Yasutaka Nishida, Atsushi Tsuruta, Kazumasa Miyake2006 Volume 75 Issue 6 Pages 064706
Published: June 15, 2006
Released on J-STAGE: August 27, 2009
JOURNAL RESTRICTED ACCESSThe behavior of the resistivity of Ce-based heavy fermion systems is studied using a 1⁄N-expansion method á la Nagoya, where N is the spin-orbital degeneracy of f-electrons. The 1⁄N-expansion is performed in terms of the auxiliary particles, and a strict requirement of the local constraints is fulfilled for each order of 1⁄N. The physical quantities can be calculated over the entire temperature range by solving the coupled Dyson equations for the Green functions self-consistently at each temperature. This 1⁄N-expansion method is known to provide asymptotically exact results for the behavior of physical quantities in both low- and high-energy regions when it is applied to a single orbital periodic Anderson model (PAM). On the basis of a generalized PAM including crystalline-electric-field splitting with a single conduction band, the pressure dependence of the resistivity ρ is calculated by parameterizing the effect of pressure as the variation of the hybridization parameter between the conduction electrons and f-electrons. The main result of the present study is that the double-peak structure of the T-dependence of ρ(T) is shown to merge into a single-peak structure with increasing pressure.View full abstractDownload PDF (511K) -
Junya Otsuki, Yoshio Kuramoto2006 Volume 75 Issue 6 Pages 064707
Published: June 15, 2006
Released on J-STAGE: August 27, 2009
JOURNAL RESTRICTED ACCESSThe non-crossing approximation (NCA) is generalized for the Anderson model with finite Coulomb repulsion U. Resummation of infinite number of terms is performed so as to incorporate all leading contributions in the limit of large degeneracy of the local states. With negligible weight of the doubly occupied local states in equilibrium, the extension is achieved through simple modifications of the lowest order formulae. The single-particle excitation spectrum is calculated with almost the same computational effort as in the original NCA. The present scheme reproduces the scaling behavior of the Kondo resonance in the density of states, and gives reasonable description of thermodynamics of the finite-U Anderson model over a wide range of temperature.View full abstractDownload PDF (409K) -
Gen Tatara, Toshihiko Takayama, Hiroshi Kohno, Junya Shibata, Yoshinob ...2006 Volume 75 Issue 6 Pages 064708
Published: June 15, 2006
Released on J-STAGE: August 27, 2009
JOURNAL RESTRICTED ACCESSThreshold current of domain wall motion under spin-polarized electric current in ferromagnets is theoretically studied based on the equation of motion of a wall in terms of collective coordinates. Effects of non-adiabaticity and a so-called β-term in Landau–Lifshitz equation, which are described by the same term in the equation of motion of a wall, are taken into account as well as extrinsic pinning. It is demonstrated that there are four different regimes characterized by different dependence of threshold on extrinsic pinning, hard-axis magnetic anisotropy, non-adiabaticity and β.View full abstractDownload PDF (191K) -
Isao Kagomiya, Hiroyuki Suzuki, Eiji Kita, Yorihiko Tsunoda, Kay Kohn, ...2006 Volume 75 Issue 6 Pages 064709
Published: June 15, 2006
Released on J-STAGE: August 27, 2009
JOURNAL RESTRICTED ACCESSMagnetization was measured for a ZnCr2O4 single crystal as a function of field direction, in a magnetic field range of 0.5–50 kOe, mainly at 5 K. To examine the effect of magnetic domain distribution, the crystal was cooled through TN, 12.2 K, with or without pressure along the [001] axis and a magnetic field of 50 kOe along the [1\\bar11] or of 60 kOe along the [0\\bar11] axis. No spontaneous magnetization was detected within the accuracy of the experiment. Above 3 kOe, the anisotropy of magnetic susceptibility decreases with increasing magnetic field, to approximately two or three orders of magnitude smaller at 30 kOe. This finding indicates that the ground state lies near the magnetically isotropic (symmetric) state but is slightly distorted. The energy difference between the symmetric state and the ground state was estimated to be on the order of 10−2 J/g or 10−3 cm−1/Cr ion, by magnetization curves. It was suggested that the magnetic symmetry of the ground state is lower than monoclinic.View full abstractDownload PDF (186K) -
Yorihiko Tsunoda, Hiroyuki Suzuki, Susumu Katano, Kiiti Siratori, Eiji ...2006 Volume 75 Issue 6 Pages 064710
Published: June 15, 2006
Released on J-STAGE: August 27, 2009
JOURNAL RESTRICTED ACCESSMotivated by recent magnetic anisotropy measurements, we performed neutron scattering experiments for a single crystal of a typical geometrical frustration system (ZnCr2O4) under a magnetic field. The magnetic structure of ZnCr2O4 is easily affected by the applied magnetic field of about 2 T. The (hh0) (h=n⁄2,n=odd) series magnetic Bragg peaks disappear when the magnetic field is applied along the [111] axis. It means that the magnetic structure turns into a new structure with higher symmetry than that in the ground state under a small magnetic field.View full abstractDownload PDF (234K) -
S. Tsuda, T. Yokoya, T. Kiss, T. Shimojima, S. Shin, T. Togasi, S. Wat ...2006 Volume 75 Issue 6 Pages 064711
Published: June 15, 2006
Released on J-STAGE: August 27, 2009
JOURNAL RESTRICTED ACCESSWe study the superconducting gap of the filled skutterudite superconductor LaRu4P12 (transition temperature Tc=7.2 K) using a newly developed sub-meV resolution photoemission spectrometer with a vacuum-UV laser as a light source. The result at 4.8 K shows the opening of a superconducting gap, whose spectral shape is well explained with an isotropic s-wave Dynes function using a gap size of 1.3 meV. This corresponds to the reduced gap 2Δ(0)⁄kBTc of 4.2. The temperature dependence of the superconducting gap shows fairly good agreement with the conventional BCS theory. The present results are consistent with those of a moderately strong-coupling and isotropic s-wave superconductor.View full abstractDownload PDF (130K) -
Khian-Hooi Chew, Yoshihiro Ishibashi, Franklin G. Shin2006 Volume 75 Issue 6 Pages 064712
Published: June 15, 2006
Released on J-STAGE: August 27, 2009
JOURNAL RESTRICTED ACCESSA one-dimensional lattice model based on the Landau–Ginzburg theory to study the intrinsic properties of a periodic superlattice with interfacial coupling is developed. The effects of thickness and interfacial coupling on the properties of a superlattice consisting of alternating ferroelectric and paraelectric constituent layers are investigated. Competition between the thickness effects of each constituent layer is expected and indeed can play an important role in governing the properties of an interface-coupled superlattice, depending on the strength of the interfacial coupling. This work may provide useful information on the possibility of manipulating structures to obtain the desired properties for specific applications.View full abstractDownload PDF (185K) -
Ikufumi Katayama, Koichiro Tanaka2006 Volume 75 Issue 6 Pages 064713
Published: June 15, 2006
Released on J-STAGE: August 27, 2009
JOURNAL RESTRICTED ACCESSWe have investigated luminescence spectra and their decay kinetics in potassium tantalate (KTaO3) to reveal the nature and dynamics of the photoexcited states. The temperature dependence of the absorption spectra indicates electron–phonon coupling in KTaO3 that is sufficiently strong to stabilize self-trapped excitons. We attribute the observed 2.5 eV luminescence to the self-trapped exciton luminescence. The decay kinetics of the 2.5 eV luminescence is found to be nonexponential with power-law behavior and shows a long lifetime of several milliseconds at 5 K, which indicates separate localization of photoexcited electrons and holes. Similar decay profiles are also observed in the oxygen-deficient and lithium-doped crystals. The decay kinetics is successfully reproduced by a model based on the tunneling recombination process. The model calculation of the excitation density dependence reveals that the number of localized electrons should be finite, which gives rise to the conductive electrons overflowing from the localized states. These results support the Maxwell–Wagner model for the photoinduced giant permittivity in KTaO3.View full abstractDownload PDF (303K) -
Masato Makino, Hideaki Koda, Masao Doi2006 Volume 75 Issue 6 Pages 064714
Published: June 15, 2006
Released on J-STAGE: August 27, 2009
JOURNAL RESTRICTED ACCESSWe found, by numerical simulation, an anomalous behavior in the average magnetic moment of a dilute suspension of magnetic particles of elongated shape under shear flow. In a shear flow v=\\dotγyex, (ex being the unit vector in x direction), upon the application of the magnetic field in y direction, magnetic moment first appears in x direction. The magnetic moment starts to orient towards y direction after the magnetic field exceeds a certain critical value. This phenomena is caused by the competition of the shear flow and the magnetic moment, and is seen when the effect of Brownian motion is negligible. When the Brownian motion is present, the anomaly becomes less obvious, but can be seen for high Peclet number. An analytical theory is given to explain the behavior.View full abstractDownload PDF (266K) -
Thang Manh Hoang, Masahiro Nakagawa2006 Volume 75 Issue 6 Pages 064801
Published: June 15, 2006
Released on J-STAGE: August 27, 2009
JOURNAL RESTRICTED ACCESSIn previous works, the chaos synchronization of multi-delay feedback systems with multi-feedback driving signal has been examined and used for designing a secure communication system. By utilizing the feature that one master can synchronize with slave(s) on multiple manifolds, a new scheme of modulation technique was proposed, i.e., synchronization manifold shift keying. In that secure communication system, the value of parameters and that of delays are kept constant in operation. In this paper, the methods which might be used for attacking the proposed secure communication system are discussed and schemes to enhance the security by means of change in the value of encoder’s parameters and that of manifolds’ delay are presented. As a result, the secure communication system can resist from existing breaking methods and future ones. The numerical simulations demonstrate and verify the effectiveness of these schemes.View full abstractDownload PDF (736K) -
Kazumi Suematsu2006 Volume 75 Issue 6 Pages 064802
Published: June 15, 2006
Released on J-STAGE: August 27, 2009
JOURNAL RESTRICTED ACCESSWithin the framework of the random distribution assumption of cyclic bonds, the preceding theory of gelation is extended to mixing systems with multifunctionalities. To examine the validity of the assumption, the theory is applied to experimental data in polyurethane network formation. The good agreement was found between the theory and experiments, in support of the soundness of the theory in the prediction of gel points and gel fraction.View full abstractDownload PDF (475K) -
Kazuki Nakanishi, Macoto Kikuchi2006 Volume 75 Issue 6 Pages 064803
Published: June 15, 2006
Released on J-STAGE: August 27, 2009
JOURNAL RESTRICTED ACCESSWe investigate aggregation mechanism of two proteins in a thermodynamically unambiguous manner by considering the finite size effect of free energy landscape of HP lattice protein model. Multi-self-overlap-ensemble Monte Carlo method is used for numerical calculations. We find that a dimer can be formed spontaneously as a thermodynamically stable state when the system is small enough. It implies the possibility that the aggregation of proteins in a cell is triggered when they are confined in a small region by, for example, being surrounded by other macromolecules. We also find that the dimer exhibits a transition between unstable state and metastable state in the infinite system.View full abstractDownload PDF (161K) -
Ryo Akiyama, Yasuhito Karino, Yasuhiro Hagiwara, Masahiro Kinoshita2006 Volume 75 Issue 6 Pages 064804
Published: June 15, 2006
Released on J-STAGE: August 27, 2009
JOURNAL RESTRICTED ACCESSIn theoretical studies on the depletion interaction between macromolecules in crowding media, usually only the macromolecules and large cosolutes are considered by assuming that the solvent can be treated as an inert background. Here, the interaction between macromolecules immersed in a solvent–cosolute mixture is calculated using the integral equation theories combined with a hard-sphere model. On the basis of the results, we point out the crucial importance of explicit incorporation of solvent molecules in the theoretical treatment. The behavior observed is highly nonlinear due to the complicated intermolecular correlations and remarkably dependent on the total packing fraction and the cosolute concentration. An example result is that the cosolute can act both as a stabilizer and as a destabilizer for a dimer of macromolecules. We present new physical pictures elucidating the behavior.View full abstractDownload PDF (145K) -
Conformational Entropy Mechanism for Periodic Motion of DNA under Constant-Field Gel ElectrophoresisRyuzo Azuma, Hajime Takayama2006 Volume 75 Issue 6 Pages 064805
Published: June 15, 2006
Released on J-STAGE: August 27, 2009
JOURNAL RESTRICTED ACCESSEntropic elasticity of a single charged polymer undergoing gel electrophoresis is a fundamental theme of polymer statistical physics since the discovery of “periodic” behavior in constant field gel electrophoresis (CFGE). In the present work we address the problem numerically by two steps. In the first step, we carry out Brownian dynamics (BD) simulations on CFGE by solving semi-microscopic Langevin equations of a polymer consisting of beads separated by a mean distance much smaller than the Kuhn length. Results are analyzed based on coarse-graining over the Kuhn length scale. We show the averaged elongation–contraction motion involves asymmetric V-shaped configurations whose shorter arm length depends on the field and the temperature consistently with what is expected when the BD chain is described by the freely-jointed chain (FJC) model with a suitable Kuhn length. To our knowledge, this is the first numerical confirmation of the FJC model itself from a submicroscopic description of polymer motion. The saturation of chain mobility in high fields agrees well with the nonlinear dependence of this shorter arm length on the field. In the second step, we discuss the periodic elongation–contraction motion of the coarse-grained chain by such a simplified model as a one-dimensional chain consisting of beads, elastic strings, and obstacles. The results from these two chain models indicate that the periodic elongation–contraction motion of DNA under CFGE is self-organized by a balance between the field force and the conformational entropic force.View full abstractDownload PDF (903K) -
Kiyotaka Miyoshi, Yusuke Takamatsu, Jun Takeuchi2006 Volume 75 Issue 6 Pages 065001
Published: June 15, 2006
Released on J-STAGE: August 27, 2009
JOURNAL RESTRICTED ACCESSDownload PDF (108K) -
Minoru Sumita, Haruhisa Ishigami, Masaru Komukae, Toshio Osaka2006 Volume 75 Issue 6 Pages 065002
Published: June 15, 2006
Released on J-STAGE: August 27, 2009
JOURNAL RESTRICTED ACCESSDownload PDF (97K) -
Chikashi Arita2006 Volume 75 Issue 6 Pages 065003
Published: June 15, 2006
Released on J-STAGE: August 27, 2009
JOURNAL RESTRICTED ACCESSDownload PDF (61K)
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