Journal of the Physical Society of Japan
Online ISSN : 1347-4073
Print ISSN : 0031-9015
ISSN-L : 0031-9015
Volume 65, Issue 12
Displaying 1-50 of 74 articles from this issue
  • Iwao Hosokawa, Shin–ichi Oide, Tsukasa Satoh, Kiyoshi Yamamoto
    Subject area: Fluid dynamics.
    1996 Volume 65 Issue 12 Pages 3683-3685
    Published: December 01, 1996
    Released on J-STAGE: October 01, 1999
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    The probability density function of lateral velocity increment across an arbitrary distance ranging from the Kolmogorov scale to the integral scale in isotropoic turbulence is predicted in a semi-empirical way. The method is based on the previous theory of the first author for treating statistics of longitudinal velocity increment and new data of direct numerical simulation of decaying isotropic turbulence on a 5123 grid.
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  • Daiju Dogen, Mieko Toida, Yukiharu Ohsawa
    Subject area: The physics of plasmas and electric discharges.
    1996 Volume 65 Issue 12 Pages 3686-3688
    Published: December 01, 1996
    Released on J-STAGE: October 01, 1999
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    Propagation of finite-amplitude magnetosonic waves in a collisionless plasma containing two ion species is studied with a one-dimensional, fully electromagnetic code based on a three-fluid model. It is found that perpendicular magnetosonic waves are damped in a two-ion-species plasma; a magnetosonic pulse accelerates heavy ions in the direction parallel to the wave front, which results in the excitation of a longer wavelength perturbation behind the pulse. The damping due to the energy transfer from the original pulse to the longer wavelength perturbation occurs even if the plasma is collisionless and the pulse amplitude is small. The theoretically obtained damping rate is in agreement with the simulation result.
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  • Yoshinori Tabata
    Subject area: Lattice dynamics and crystal statistics.
    1996 Volume 65 Issue 12 Pages 3689-3691
    Published: December 01, 1996
    Released on J-STAGE: October 01, 1999
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    A stable solitary wave in the diatomic Toda lattice was found by means of numerical calculation.This wave can occur when the mass ratio (μ) of the two kinds of particles in the diatomic Toda lattice is 0.320191 in the case that the two Toda potential parameters are equal to unity.The stability was confirmed over a long period up to t=50, 000.
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  • Tomozo Tomoyose, Akira Fukuchi, Masaru Aniya
    Subject area: Electron states in condensed matter.
    1996 Volume 65 Issue 12 Pages 3692-3695
    Published: December 01, 1996
    Released on J-STAGE: October 01, 1999
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    Effective charges of superionic conductors are calculated by using a microscopic dielectric function which is composed of valence electron and localized d electron terms. The d electron terms of the effective charge are evaluated by using the tight-binding approximation. It is found that the d electrons enhance the transverse effective charge.
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  • Susumu Sasaki, Azusa Matsuda, C. W. Chu
    Subject area: Electron states in condensed matter.
    1996 Volume 65 Issue 12 Pages 3696-3699
    Published: December 01, 1996
    Released on J-STAGE: October 01, 1999
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    We report a study of 13C NMR spin-lattice relaxation in the superconducting fulleride K3C60 at low temperatures (T). The experimentally obtained relaxation data, which are scaled to a T-independent relaxation shape, are found to be well reproduced by the anisotropy parameter α spin ≡ Aisospin/Aaxspin, where Aisospin and Aaxspin are the isotropic and anisotropic part of the 13C hyperfine coupling of conduction electrons, respectively. Simulation for a powder sample with various α spin values indicates that the deviation from a single-exponential relaxation is largest when the hyperfine coupling is isotropic to some extent (i.e., α spin ≈ 0.5) instead of purely anisotropic (i.e., α spin = 0). These results justify a model based on the electronic single site. Moreover, from the validity of the extended Korringa relation with K(α ) = 5.7, it is found that the electronic state is a Fermi liquid in which the relaxation rate is enhanced substantially by the antiferromagnetic electron interaction.
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  • Satoshi Fujimoto, Norio Kawakami
    Subject area: Electronic transport in condensed matter.
    1996 Volume 65 Issue 12 Pages 3700-3703
    Published: December 01, 1996
    Released on J-STAGE: October 01, 1999
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    We investigate the system-size dependenceas well as the temperature dependence of theconductance in 1D electron systems, paying particularattention to the effect of Umklapp scattering.By taking into account the renormalization ofthe external potential due to electron-electron interaction, the correction to the conductance, 2e2/h, due to Umklapp scattering is estimated perturbatively.The Tomonaga-Luttinger liquid parameter appearsin the conductance via the system-size and temperature dependence.
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  • Shingo Katsumoto, Mitsuru Kimura
    Subject area: Electronic transport in condensed matter.
    1996 Volume 65 Issue 12 Pages 3704-3707
    Published: December 01, 1996
    Released on J-STAGE: October 01, 1999
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    We report the current-voltage characteristics of a single-electron circuit, in which the Coulomb island of a single-electron transistor is connected to the source electrode of another transistor.The Josephson-like current of one of the transistors was tuned by adjusting the gate voltage of the other, reflecting the uncertainty relation between the phase difference and the particle number. We found that the “parity effect” or “even-odd asymmetry” was also affected by the gate voltage of the other transistor. A possible explanation for this asymmetry-tuning is presented.
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  • Shiro Kawabata, Katsuhiro Nakamura
    Subject area: Electronic transport in condensed matter.
    1996 Volume 65 Issue 12 Pages 3708-3711
    Published: December 01, 1996
    Released on J-STAGE: October 01, 1999
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    The existence of hc/2e oscillation of magneto-conductance, analogous to the Al'tshuler-Aronov-Spivak (AAS) effect in disordered metal rings, is theoretically predicted for experimentally-realizable ballistic Aharonov-Bohm (AB) billiards. The diagonal term of the wave-number averaged reflection probability δ RD(Φ) is calculated for chaotic and integrable (and mixed) billiards by use of the semiclassical scattering theory. We find that the difference between chaotic and integrable (and mixed) classical scatterings produces qualitatively different formulas for δ RD(Φ) with their behavior determined only by knowledge regarding the underlying classical dynamics. These formulas provide a new testing ground for exploring quantum chaos.
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  • Arisato Kawabata, Tobias Brandes
    Subject area: Electronic transport in condensed matter.
    1996 Volume 65 Issue 12 Pages 3712-3715
    Published: December 01, 1996
    Released on J-STAGE: October 01, 1999
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    We investigate the effect of electron-electron interactions on the transport properties of disordered quasi one-dimensional quantum wires with two or more subbands occupied. We apply two alternative methods to solve the logarithmic divergent problem, namely the parquet graph theory and a renormalization group calculation. We solve the group equations analytically in the weak coupling limit and find a power law for the temperature dependent conductivity of a multi-channel system. The exponent is roughly equal to the inverse of the number of the occupied subbands.
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  • Tohru Okamoto, Shinji Kawaji
    Subject area: Electronic structure and electrical properties of surfaces, interfaces and thin films.
    1996 Volume 65 Issue 12 Pages 3716-3719
    Published: December 01, 1996
    Released on J-STAGE: October 01, 1999
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    We have studied a possible ring-exchange process of neighboring three electrons in a triangular lattice formed in a Si inversion layer.In the absence of the normal component of the magnetic field, the exchange leads to ferromagnetic interaction between nearest neighbor spins.When there is a finite magnetic flux through the exchange path, the Aharonov-Bohm effect drastically changesthe nature of the exchange interaction.Such a picture clearly explainsthe observed peculiar dependence of activation energyon the magnetic field and its direction.
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  • Kazushige Machida, Masa–aki Ozaki, Tetsuo Ohmi
    Subject area: Superconductivity.
    1996 Volume 65 Issue 12 Pages 3720-3723
    Published: December 01, 1996
    Released on J-STAGE: October 01, 1999
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    The odd-parity pairing states are classified group-theoretically under tetragonal symmetry and characterized when the spin-orbit coupling is weak. The classified states include higher orbital angular momentum p, f, … -wave pairing.In connection with a layered perovskite superconductor, Sr2RuO4, prominent physical properties of the non-unitary state such as the spontaneous moment, large residual density of states and the spontaneous lattice distortion are highlighted to help to distinguish it from other triplet and singlet states.
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  • Naoto Nagaosa, Akira Furusaki, Manfred Sigrist, Hidetoshi Fukuyama
    Subject area: Magnetic properties and materials.
    1996 Volume 65 Issue 12 Pages 3724-3727
    Published: December 01, 1996
    Released on J-STAGE: October 01, 1999
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    The effect of nonmagnetic impurities in the two-leg Heisenberg laddersystem and other spin liquids with excitation gap is discussed.It is shown that the random depletion of spins introduces a randomBerry phase term into the nonlinear σ model.The classical nature of the antiferromagnetic correlation is enhancedby the topological decoherence, and the staggered susceptibility showsmore singular behavior at low temperatures than the uniformantiferromagnetic Heisenberg chain.
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  • Youichirou Iino, Masatoshi Imada
    Subject area: Magnetic properties and materials.
    1996 Volume 65 Issue 12 Pages 3728-3731
    Published: December 01, 1996
    Released on J-STAGE: October 01, 1999
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    Effects of nonmagnetic impurity doping on an antiferromagnetic spin-1/2 Heisenberg ladder system are studied by the quantum Monte Carlo method.A single nonmagnetic impurity induces a localized spin-1/2 moment accompanied by static and enhanced antiferromagnetic correlations around it.A small and finite concentration of impurities induces a remarkable change ofmagnetic and thermodynamic properties with gapless excitations.It also shows rather sharp but continuous crossover around a impurity concentration of about 4%.Above the crossover concentration, all the spins are strongly coupled, participating in the enhanced and rather uniform power-law decay of the antiferromagnetic correlation.Below the crossover concentration, each impurity forms an antiferromagnetically correlated cluster only weakly coupled each other.For random distribution of impurities, large Curie-like susceptibility accompanied with small residual entropy is obtained at low temperatures, in agreement with recent experimental observation in Zn-doped SrCu2O3.The temperature dependence of antiferromagnetic susceptibility shows power-law-like but weaker divergence than the single chain antiferromagnet in the temperature range studied.
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  • Harumi Sakamoto, Kenn Kubo
    Subject area: Magnetic properties and materials.
    1996 Volume 65 Issue 12 Pages 3732-3735
    Published: December 01, 1996
    Released on J-STAGE: October 01, 1999
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    We examined a one-dimensional Hubbard model withnearest- and next-nearest-neighbor hopping with up to 32 sites by means of the density-matrix renormalization-group method. The model has two energy bands and includes the flat-band model studied by Tasaki as a special case. The model with finite band dispersion is found to show metallic (saturated) ferromagnetism for a sufficiently strong interaction.No partially polarized ground state is found.The interaction necessary to realize a ferromagnetic ground statebecomes weak when the electron density is decreased from the quarter-filling.
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  • Kazuma Hirota, Nobuhisa Kaneko, Akinori Nishizawa, Yasuo Endoh
    Subject area: Magnetic properties and materials.
    1996 Volume 65 Issue 12 Pages 3736-3739
    Published: December 01, 1996
    Released on J-STAGE: October 01, 1999
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    Neutron-scattering experiments have been performed on a LaMnO3 singlecrystal. The spin waves exhibit two-dimensional anisotropic dispersion, that is, strong planar ferromagnetic coupling and weak antiferromagneticinterplane coupling with a finite gap. The critical exponent β of theorder parameter is 0.25 ± 0.01, which is much smaller than valuesobtained for the three-dimensional Ising (0.326) and Heisenberg (0.367) models. Ferromagnetic spin-wave-like dispersion remains for ω > 10 meV atTc ≈ 140 K, though the spectrum near the zone center is entirelyoverdamped around ω = 0.
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  • Haruhiro Hiraka, Yasuo Endoh
    Subject area: Magnetic properties and materials.
    1996 Volume 65 Issue 12 Pages 3740-3742
    Published: December 01, 1996
    Released on J-STAGE: October 01, 1999
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    The effects of external pressure and the substitution of S by Se on the ferromagnetic phase transtion in CoS_2 were studied by magnetization measurements.Both operations reduced Tc, made the magnetic phase transition discontinuousand gave rise to the metamgnetic transition immediately above Tc.In terms of the phenomenological Landau theory, our experimental results are consistently interpreted on the basis of the variation of the fourth coefficient (F4)from a small positive value through zero to a negative value by varying Se-concentration or applying pressure.The appearance of weak metamagnetic transition in CoS2 at ambient pressure also supports that F4 is nearly equal to zerounder the external field.Therefore, the anomalous critical exponents in CoS2 reflect the tricritical behavior, as in the previous argument.
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  • Kazuhiro Murata, Shin–ichi Kuroda, Yukihiro Shimoi, Shuji Abe, T ...
    Subject area: Magnetics resonances and relaxations in condensed matter; MÖssbauer effect.
    1996 Volume 65 Issue 12 Pages 3743-3746
    Published: December 01, 1996
    Released on J-STAGE: October 01, 1999
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    Light-induced ESR (LESR) measurements have been performed on undoped poly(paraphenylene vinylene) (PPV) down to 4K. The ESR signal increases significantly for the excitation energy above 3.1--3.2eV, as in the case of the excitation spectra of photocarriers reported in PPV derivatives. The anisotropic light-induced ESR spectra in oriented samples are well reproduced by the spectra calculated using a theoretical polaron spin distribution in the case of finite electron-electron interaction. These spectral features indicate that the observed spins are photogenerated polarons.
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  • Yutaka Itoh, Masahiro Matsumura, Hideki Yamagata
    Subject area: Magnetics resonances and relaxations in condensed matter; MÖssbauer effect.
    1996 Volume 65 Issue 12 Pages 3747-3750
    Published: December 01, 1996
    Released on J-STAGE: October 01, 1999
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    The temperature (T) dependence of the planar 63Cu nuclear spin-lattice relaxation rate (1/T1) and its anisotropy have been measured for 63Cu-enriched high-Tc Cu oxides, La2-xSr_xCuO4 (x=0.13, Tc-- 34K; and 0.18, Tc-- 35K), where the Cu(A) and the Cu(B) resonance lines are clearly discriminated. We found that 1/T1T shows a sharp maximum at 45--50K above Tc. From the T-dependent anisotropy of 1/T1, possible origins for the peak of 1/T1T are discussed based on current spin fluctuation theories.
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  • Yutaka Itoh, Takato Machi, Atsushi Fukuoka, Keiichi Tanabe, Hiroshi Ya ...
    Subject area: Magnetics resonances and relaxations in condensed matter; MÖssbauer effect.
    1996 Volume 65 Issue 12 Pages 3751-3753
    Published: December 01, 1996
    Released on J-STAGE: October 01, 1999
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    We observed the pseudo spin-gap behavior of spin excitations in lightly doped single-CuO2-layer HgBa2CuO4+δ (Tc=50, 72 and 80, K) using the Cu NMR spin-echo technique. The results indicate that lightly doped high-Tc Cu oxide inherently possesses the pseudo spin-gap.
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  • Norio Ogita, Tsutomu Minami, Yoshifumi Tanimoto, Osamu Fujita, Jun Aki ...
    Subject area: Optical properties and condensedmatter spectroscopy and other interactions of matter with particles and radiation.
    1996 Volume 65 Issue 12 Pages 3754-3757
    Published: December 01, 1996
    Released on J-STAGE: October 01, 1999
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    Detailed temperature dependence of (c, c) Raman scattering spectra has been measured for CuGeO_3 in the vicinity of spin-Peierls transitiontemperature (Tsp). Below Tsp, six peaks at 30, 105, 227, 370, 416, and 817 cm-1 have been observed. We newly observed a peak at 416 cm-1. The energy of the 30 cm-1 peak decreases continuously with increasing temperature and becomes zero above Tsp. The peak at 30 cm-1 is assigned as the soft mode in the spin-Peierls phase from the agreement with the temperature dependence of the super-lattice reflection intensity. The peak at 227 cm-1 is assigned as a two-magnon along the c-axis (Cu chain direction). The peaks at 370, 416, and 817 cm-1 are assigned as the phonons, which appear by the symmetry change. The new peaks of (c, c) are not sensitive to the magnetic field along the a-axis below 9 T at 4.7 K.
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  • Shozo Takeno
    Subject area: Mathematical methods in physics.
    1996 Volume 65 Issue 12 Pages 3759-3768
    Published: December 01, 1996
    Released on J-STAGE: October 01, 1999
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    A lattice Green's function theory is formulated to give a band-theoretical interpretation of stationary nonlinear localized modes (SNLM) in pure nonlinear lattices. In one-dimensional lattices and in its simplest form in higher-dimensional cases, the theory yields the eigenfrequency ω of the SNLM in terms of the frequency ω 0(q) (q is the wave vector) of the corresponding linear lattice in the form ω =ω 0(q0+iK), where q0 is an edge point of the Brillouin zone of ω 0(q), and K≡ K(A) is a parameter depending on the localized mode amplitude A. Such a result and more general ones involving lattice Green's functions lead to the ubiquity of the existence of the SNLM irrespective of the lattice dimensionality as approximate nonlinear modes in nonintegable lattices and its similarity to force-constant defect modes. Stationary solitons in the Ablowitz-Ladik lattice can be considered as an example of the SNLM in integrable lattices.
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  • Nobuyoshi Ohta
    Subject area: Mathematical methods in physics.
    1996 Volume 65 Issue 12 Pages 3769-3775
    Published: December 01, 1996
    Released on J-STAGE: October 01, 1999
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    A collective field method is extended to obtain all the explicit solutions ofthe generalized Calogero-Sutherland models that are characterizedby the roots of all the classical groups, including the solutionscorresponding to spinor representations for BN and DN cases.
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  • Juan Garía–Escudero
    Subject area: Mathematical methods in physics.
    1996 Volume 65 Issue 12 Pages 3776-3779
    Published: December 01, 1996
    Released on J-STAGE: October 01, 1999
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    A class of four-colour heptagonal selfsimilar patterns is studied. Two equivalent algebraic descriptions for the generation of the patterns are considered, allowing to obtain recursion relations for the Fourier amplitudes and also positions for the Bragg peaks.
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  • Hidetoshi Nishimori, Yoshihiko Nonomura
    Subject area: Statistical physics and thermodynamics.
    1996 Volume 65 Issue 12 Pages 3780-3796
    Published: December 01, 1996
    Released on J-STAGE: October 01, 1999
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    We develop the statistical mechanics of the Hopfield model ina transverse field to investigate how quantum fluctuationsaffect the macroscopic behavior of neural networks.When the number of embedded patterns is finite, the Trotterdecomposition reduces the problem to that of a random Isingmodel. It turns out that the effects of quantum fluctuationson macroscopic variables play the same roles as those of thermal fluctuations.For an extensive number of embedded patterns, we apply the replica method to the Trotter-decomposed system. The result is summarized as a ground-state phase diagram drawn in terms of the number of patterns per site, α, and the strength of the transverse field, Δ. The phase diagram coincides very accurately with that of the conventional classical Hopfield model if we replace the temperature T in the latter model byΔ. Quantum fluctuations are thus concluded tobe quite similar to thermal fluctuations in determination of the macroscopic behavior of the present model.
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  • Tatsuya Uezu, Yoshiyuki Kabashima, Kazuo Nokura, Naomi Nakamura
    Subject area: Statistical physics and thermodynamics.
    1996 Volume 65 Issue 12 Pages 3797-3809
    Published: December 01, 1996
    Released on J-STAGE: October 01, 1999
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    We study learning from examples by a perceptron when a return to an example is given by a stochastic relation which is represented by the conditional probability distribution P(u), where uis proportional to the inner product between theoptimal synaptic weight vector and the example vector. The problem is analyzed by replica method in the case of spherical weights.Since the replica symmetric(RS) solution turns out to be unstable for stochastic cases, we consider the one-step replica symmetry breaking (RSB) solution.We investigate the asymptotic behavior of the learning curve as α ≡ \frac{p}{N} → ∞, wherep is the number of samples and N is the dimension of the synaptic weights.The average generalization error ε gis expressed as (ε g - ε min) ∝ α - γin the asymptotic region.For the minimum-error algorithm, we find γ=\frac{1+δ}{1+3δ} for the RS solution and γ=\frac{1+δ}{1+2δ} for the one-step RSB solution in the case of the function P(u) which is monotonic and expressedas P(u) ~= const. + a sgn(u)|u| δ around u =0 .That is, the exponent γ is determined by the local property of P(u) around u=0.In particular, for the case of δ=1, the one-step RSB ansatz, unlike the RS ansatz, gives thesame result up to a logarithmic correction as previous results obtained by non-replica methods in the one-dimensional model.
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  • Takao Yamamoto
    Subject area: Statistical physics and thermodynamics.
    1996 Volume 65 Issue 12 Pages 3810-3818
    Published: December 01, 1996
    Released on J-STAGE: October 01, 1999
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    A new coarse-grained terrace-step-kink (TSK) picture for the vicinal surface is proposed.In this picture called harmonically-interacting step (HIS) picture, the vicinal surface is expressed by an assembly of the harmonically-interacting steps which look like flexible continuous strings.Through the transfer matrix representation, we show the equivalence between the HIS picture and the capillary wave picture for the vicinal surface in the length-scale much larger than the average step-spacing.To establish the validity and to show the usefulness of the HIS picture, we pay attention to the step deformation width.The deformation width is studied both by the analytic calculation based on the HIS picture and by the Monte-Carlo calculations for the free-Fermion TSK model and for the solid-on-solid step TSK model.The results from these calculations agree very well.
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  • Hideaki Ujino, Miki Wadati
    Subject area: Statistical physics and thermodynamics.
    1996 Volume 65 Issue 12 Pages 3819-3823
    Published: December 01, 1996
    Released on J-STAGE: October 01, 1999
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    Thermodynamics of the quantum Calogero model is studied by themicrocanonical ensemble approach.We formulate a thermodynamic Bethe ansatz (TBA), whose referencestate is the generalized ideal gas with fractional statistics(free a-on).Using the a-onic TBA, the free-quasiparticle picture forthe Calogero model is identified as the free a-on.We calculate the thermodynamic potential and the distribution functionfor the Calogero model in the thermodynamic limit.The thermodynamic potential at thermal equilibrium can be understoodby the Bernoulli equation.We also show that the thermodynamics of the Calogero model andthe Sutherland model are the same except for the dispersion relations.
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  • Akihiro Taniguchi, Tomohiko Ikuta, Akihiko Osa, Hiroshi Yamamoto, Kiyo ...
    Subject area: Nuclear structure.
    1996 Volume 65 Issue 12 Pages 3824-3834
    Published: December 01, 1996
    Released on J-STAGE: October 01, 1999
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    The level structure of 153Pm has been studied from the decay of 153Nd. The radioactivities of 153Nd were separated from the fission products of 235U using the upgraded KUR-ISOL. A precise decay scheme of 153Nd has been constructed up to 2, MeV and 115 γ -rays and 36 levels were involved in the decay scheme, in which 107 γ -rays and 28 levels were newly observed. The multipolarities and E2/M1 mixing ratios of 11 γ -transitions were deduced from the measurement of internal conversion electrons. From the results of the angular correlation measurements, the spin values of 450.5, 105.4 and 32.3, keV levels were deduced to be 3/2+, 7/2+ and 5/2+, respectively and the previous assignments were confirmed. The half-lives of 32.3 and 105.4, keV levels were determined to be 1.2(1), ns and 0.44(2), ns, respectively and the enhanced E1 transitions with B(E1)=10-3-- 10-4, W.u. were observed. The 153Pm level structure was compared with the result of a calculation with a rotation-vibration coupling model (RVCM) and it was found that 153Pm has a typical nuclear structure of the deformed nucleus. Moreover, the observation of enhanced E1 transitions between parity doublet bands indicates the possibility of the existence of the reflection asymmetric deformation in 153Pm.
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  • Kazuo Minami, Xiaodong Zheng, Masaaki Ota, Md. Ruhul Amin, Koji Tanaka ...
    Subject area: Electricity and magnetism: fields and charged particles.
    1996 Volume 65 Issue 12 Pages 3835-3841
    Published: December 01, 1996
    Released on J-STAGE: October 01, 1999
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    Linear dispersion relation for an axisymmetric metal-wall slowwave structure (SWS) with double period corrugations has beenanalyzed numerically. The double period SWS is here proposed forimproving the oscillation frequency performance of high-power backwardwave oscillators that maysustain stable oscillation despite the energy exhaustion ofthe driving electron beam from upstream to downstream in the SWS.It is shown that conventional TM01 mode in a single period SWSis split into a number of isolated branches. Oscillation frequencies arekept comparatively unchanged rather than the case of single period SWS.
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  • Hiroshi Miyazaki, Yoji Jimba, Chong–Yeal Kim, Takeshi Watanabe
    Subject area: Optics.
    1996 Volume 65 Issue 12 Pages 3842-3852
    Published: December 01, 1996
    Released on J-STAGE: October 01, 1999
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    The concept of local photonic lattice (PL) is introduced in 1D photonic lattices (PL's) to interpret the defects as donor-like or acceptor-like within any band gap of the host PL. Based on the concept of the local PL, an analysis is presented on the tunability of a movable defect which would be used as a tunable frequency filter. By further extending the local PL, we introduce a 1D photonic well composed of the well-like 1D PL sandwiched by the barrier-like 1D PL's. Similarity is investigated between the 1D photonic wells and the semiconductor quantum wells (QW's). It is shown that the bound states are well described by the effective “mass” approximation in analogy to the QW's. These bound states appear as sharp peaks in the transmission spectrum of the finite size 1D photonic well.
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  • Jun–ichi Ueda, Yoshiro Sadamoto, Yasuko Nishiyama, Kenji Fukushi ...
    Subject area: Mechanics, elasticity, and rheology.
    1996 Volume 65 Issue 12 Pages 3853-3857
    Published: December 01, 1996
    Released on J-STAGE: October 01, 1999
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    The anelasticity of elastic substances now attracts an intense attention of physicists who attempt more precise definition of the Newtonian constant of gravitation and also the detection of gravitational waves. In this context a close understanding of the anelasticity seems to be hasted. We in this paper propose a new dynamical model of the anelasticity which closely reflects the motion of impurities, grain walls, crystalline defects and so on embodied in elastic substances and subjected to applied stress. Recently Ueda and Sadamoto observed an anomalous frequency dependence of the effective-mass in the spring-mass system, which seemed due to the anelasticity and turned out not explainable in terms of a usual visco-elastic model. The new model is shown to be consistent with their experiment and the effective-mass-ratio analysis used by them is demonstrated to be very powerful to determine the anelasticity parameters involved.
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  • Masaru Shinohara
    Subject area: Fluid dynamics.
    1996 Volume 65 Issue 12 Pages 3858-3861
    Published: December 01, 1996
    Released on J-STAGE: October 01, 1999
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    An experimental investigation has been made of the lateral velocity of two spherical particles sedimenting symmetrically about the axis of a vertical circular cylinder. The particle Reynolds number is in the range of 0.025--0.171. The ratio of the particle radius to the cylinder radius is in the range of 0.0086--0.0174. The particles sedimenting near the cylindrical wall leave the wall and those sedimenting near the axis migrate away from the axis. The experimental results show that two spheres move to an equilibrium position at a distance from the axis of about 0.4 times the cylinder radius. This is much different from the result of a single small sphere which moves to the axis of a cylinder.
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  • Keisuke Araki, Shinichiro Yanase, Jiro Mizushima
    Subject area: Fluid dynamics.
    1996 Volume 65 Issue 12 Pages 3862-3870
    Published: December 01, 1996
    Released on J-STAGE: October 01, 1999
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    The effect of a weak azimuthal shear flow on the Bénardconvection in a spherical shell is investigated numerically wheregravity is directed to the center of the spheres. Differential rotation of the spheres is introduced as the simplestdriving mechanism of the shear flow. Axisymmetric steady solutions are obtained by an iterative methodand their stability is analyzed. Bifurcation diagram of the steady solutions is extensively searchedover the parameter space. It is shown by both the fully numerical calculation and the weaklynonlinear analysis that the weak shear flow breaks the asymptoticreflection symmetry due to the self-adjointness of the linearizedsystem so that the pitchfork bifurcation is deformed and thesaddle-node bifurcation occurs.
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  • A. L. A. Fonseca, J. L. Ferreira, O. A. C. Nunes
    Subject area: The physics of plasmas and electric discharges.
    1996 Volume 65 Issue 12 Pages 3871-3876
    Published: December 01, 1996
    Released on J-STAGE: October 01, 1999
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    The problem of plasmon instability of an electron-plasmon system is studied. When the plasma electron have a net drift velocity relative to the background of positive charges in the presence of a static, strong, uniform magnetic field, it is found that the plasmons may become unstable when certain value for the drift velocity is exceeded. We have studied both the general case of arbitrary Landau quantum number n and the extreme quantum limit (EQL) where the electrons are all accomodated in the lowest Landau level. In the EQL (n=0) provided the electron cyclotron energy is greater than the thermal energy the plasmon instability occurs but it is restricted to magnetic field values greater than a critical value.
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  • Yasuaki Kishimoto
    Subject area: The physics of plasmas and electric discharges.
    1996 Volume 65 Issue 12 Pages 3877-3889
    Published: December 01, 1996
    Released on J-STAGE: October 01, 1999
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    A model which describes the nonlinear evolution of the radiation field in a high current Raman regime free-electron laser with a rectangular waveguide is presented. In the presence of the electrostatic field (i.e. the plasma wave), although the TE and TM modes which are completely separated eigen-modes in a vacuum waveguide couple with each other, the coupling is found to be weak and decoupled by taking the wiggler average. Such weak coupling allows one to derive the equation to determine the electrostatic field which can be solved by introducing the Gould-Trivelpiece (G-T) mode expansion method. We apply the model to investigate the effect of space charge on the amplification of the FEL by using a self-focusing wiggler which has parabolically shaped pole faces with a relatively low beam energy of around 1, MeV. The electrostatic field significantly affects the dispersion especially for higher mode number of the radiation. It is found that the electrostatic field makes the resonance condition strict, so that the dispersion relation reveals fine structure, reflecting the spatial distribution of the beam and the 3-dimensional particle motion.
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  • Kohtaro Orito
    Subject area: The physics of plasmas and electric discharges.
    1996 Volume 65 Issue 12 Pages 3890-3895
    Published: December 01, 1996
    Released on J-STAGE: October 01, 1999
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    The quasi-two-dimensional nonlinear equations for drift and Rossby vortices have some stationary multipole solutions, and especially the dipole vortex solution is called modon.These solutions are valid only in the lowest order where the fluid velocity has a stream function.In order to investigate features of the multipole solutions more accurately, the effect of the higher order terms, for example the polarization drift in a plasma or the Coriolis force in a rotating planet, needs to be considered.It is shown that the higher order analysis through a new technique based on a transformation of variables is much easier than a straightforward iteration.The solutions in this analysis are obtained by inverse transformation to the original coordinates, where the profiles of potentials are distorted by the effects of higher order terms.
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  • Wei Wang, Takeji Hashimoto
    Subject area: Structure of liquids and solids; crystallography.
    1996 Volume 65 Issue 12 Pages 3896-3900
    Published: December 01, 1996
    Released on J-STAGE: October 01, 1999
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    We have observed the coalescence process of elementary nematic droplets having either radial or bipolar structure. The coalescence causes symmetry-breaking in elementary droplets and then creates new defects either in the bulk or at the surface of the coalesced droplet; the defects annihilate and the shape of the droplets after coalescence changes, resulting in symmetry-recovering and formation of the larger droplets which have the same structure as the former ones. We found that the number and feature of the defects formed and then annihilated during ordering processes can be precisely interpreted in terms of the topological theorems: the Gauss theorem for the droplets with the normal boundary condition, and the Poincaré theorem for the droplets with the tangential boundary condition.
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  • Toshihiko Yokoyama, Yoshiki Yonamoto, Toshiaki Ohta
    Subject area: Structure of liquids and solids; crystallography.
    1996 Volume 65 Issue 12 Pages 3901-3908
    Published: December 01, 1996
    Released on J-STAGE: October 01, 1999
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    We have measured and analyzed the temperature dependence of extended X-ray absorption fine structure (EXAFS) spectra of tetrahedral systems MBr4 (M=C, Si, Ge). The EXAFS analysis by means of the cumulant expansion technique enables one to obtain information about force constants including the third-order anharmonicity. The second-order cumulants obtained experimentally are in excellent agreement with the values expected by the vibrational data and the third-order cumulants have been determined successfully. For the first nearest neighbor (NN) Br--M shells the stretching motions are apparently dominant to describe EXAFS, while for the second NN Br--Br shell the bending modes are found to contribute significantly to the cumulants especially for the third-order anharmonicity. The obtained force constants are compared to each other and the origin of observed bending anharmonicity is discussed.
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  • Toshihiko Yokoyama, Toshiaki Ohta
    Subject area: Structure of liquids and solids; crystallography.
    1996 Volume 65 Issue 12 Pages 3909-3914
    Published: December 01, 1996
    Released on J-STAGE: October 01, 1999
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    We observed a noticeable dynamical effect of the scattering amplitude in Br K-edge extended X-ray-absorption fine structure (EXAFS) spectra of linear triatomic CuBr2-. The conventional static treatment of the scattering amplitude was found to give appropriate thermal damping for the first-nearest neighbor (NN) Br--Cu shell, while it showed fatal discrepancy for the second-NN Br--Br shell which contains strong multiple-scattering paths due to the collinear arrangement. We have thus employed the dynamical treatment of the scattering amplitude for the second-NN shell with the assumption of the harmonic oscillators. The thermal damping of the second-NN shell was estimated appropriately by taking the bending motions into account. The present study gives the first clear example for the dynamical effect of the scattering amplitude and indicates that great care should be taken in the analysis of higher-NN shells containing multiple-scattering paths.
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  • Hisashi Hiramoto, Mahito Kohmoto
    Subject area: Lattice dynamics and crystal statistics.
    1996 Volume 65 Issue 12 Pages 3915-3919
    Published: December 01, 1996
    Released on J-STAGE: October 01, 1999
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    We study the classical vibration problem of a chain with spring constants which are modulated in a quasiperiodic manner, i.e., a model in which the elasticenergy is ∑jkj( uj-1-uj)2, where kj=1+Δcos[2πσ(j-1/2)+θ] and σ is an irrational number. For Δ < 1, it is shown analytically that the spectrum is absolutely continuous, i.e., all theeigen modes are extended. For Δ=1, numerical scaling analysis shows that the spectrum is purely singular continuous, i.e., all the modes are critical.
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  • Takashi Itoh, Tetsuya Yamagata, Hiroya Ishikawa, Masato Hashimoto, Tak ...
    Subject area: Equations of state, phase equilibria, and phase transitions.
    1996 Volume 65 Issue 12 Pages 3920-3925
    Published: December 01, 1996
    Released on J-STAGE: October 01, 1999
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    Intra- and intermolecular interactions in nylon 66 crystal are calculated mainly using internal rotation and Lennard-Jones potential functions reasonably supposing that the amide planes are fixed and the hexamethylene moiety in the chain has an inversion center. Partition function is formularized on the basis of sum of the intra- and intermolecular interaction potentials in analogy with the Ising model on a rectangular lattice with degeneracy of interaction energy to show that the first-order phase transition occurs when the transition temperature Tt is lower than the critical temperature Tc and the second-order phase transition does when Tt=Tc, where Tc only depends on the intermolecular interaction and Tt on the intramolecular one mainly. The pressure effect on this phenomenon is qualitatively explained from temperature- or Δd (d100-d110, 010)-dependence of Tc and Tt.
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  • D. –Y. Kim, Y. S. Cho, S. –I. Kwun
    Subject area: Equations of state, phase equilibria, and phase transitions.
    1996 Volume 65 Issue 12 Pages 3926-3930
    Published: December 01, 1996
    Released on J-STAGE: October 01, 1999
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    The normal-incommensurate phase transition of K2ZnCl4 and [N(CH3)4]2ZnCl4 were studied by the linear birefringence method for the determining critical exponent, β . The critical linear birefringence behavior can well be described by standard 3-d XY model over the temperature range 10-3<(Ti-T)/Ti<10-2. The effect of symmetry breaking was not found in both K2ZnCl4 and [N(CH3)4]2ZnCl4. So we can determine the critical exponent β directly from linear birefringence by scaling analysis. As the temperature was decreased in K2ZnCl4 the critical linear birefringence behavior asymptotically approach to the prediction of classical mean field theory.
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  • Yasumitsu Matsuo, Junko Hatori, Katsumi Irokawa, Masaru Komukae, Toshi ...
    Subject area: Equations of state, phase equilibria, and phase transitions.
    1996 Volume 65 Issue 12 Pages 3931-3934
    Published: December 01, 1996
    Released on J-STAGE: October 01, 1999
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    Thermal, dielectric, X-ray and optical investigations of Tl2SeO4 were carried out above room temperature. It was found that Tl2SeO4 undergoes an improper ferroelastic phase transition at 388°C, and has spontaneous strain as=(e22-e33)/2 = 1.97 × 10-2 at room temperature. Tl2SeO4 shows domain structures composed of three kinds of orientations with two types of domain boundaries. The crystal belongs to the space group P63/mmc with the hexagonal unit cell parameters of ah=6.295(6) Å and ch=8.189(5) Å at 410°C . It was deduced that the improper ferroelastic phase transition is characterized by the symmetry change from P63/mmc to Pnam.
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  • Kêichiro Aizu
    Subject area: Equations of state, phase equilibria, and phase transitions.
    1996 Volume 65 Issue 12 Pages 3935-3937
    Published: December 01, 1996
    Released on J-STAGE: October 01, 1999
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    U- (or H-) ferroelectricity is ferroelectricity that should (or should not) vanish if the prototypic phase is brought from being undulated to homogeneity. This paper deals only with H-ferroelectricity. For simplicity the order parameter system is assumed to comprise only one real variable. Prototype undulation exerts certain influences upon H-ferroelectricity. As one of these influences, prototype undulation causes the following distinction for the paraelectric to ferroelectric transition. If the direction of prototype undulation is perpendicular to the ferroelectric direction, the transition is amplitudinal. If parallel, phase-differential. (In the case of homogeneous prototype, no such distinction exists; the transition is neither amplitudinal nor phase-differential.) A detailed theory on the distinction is given.
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  • Sergey V. Dmitriev, Kohji Abe, Takeshi Shigenari
    Subject area: Equations of state, phase equilibria, and phase transitions.
    1996 Volume 65 Issue 12 Pages 3938-3944
    Published: December 01, 1996
    Released on J-STAGE: October 01, 1999
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    A simple one-dimensional crystal model was proposed in order to study theincommensurate phase formation and its properties were numerically analyzed.In this model each particle (molecule) of the crystal has two degrees of freedomso that a longitudinal sound wave propagation is possible. In the case of smalldisplacements and incompressible molecules the model has the Hamiltonianidentical to that for a linear chain with a local fourth orderanharmonic potential and the harmonic nearest- and next-nearest-neighborinteractions. Particular emphasis has been placed on the analysisof the incommensurate phases caused by the soft modes with short wavelengthwhich has not been studied in most of the previous investigations.
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  • Taku Seki, Yoshio Kuramoto, Tomotoshi Nishino
    Subject area: Electron states in condensed matter.
    1996 Volume 65 Issue 12 Pages 3945-3951
    Published: December 01, 1996
    Released on J-STAGE: October 01, 1999
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    This paper investigates origin of the extra stability associated with particular values (magic numbers) of the total angular momentum of electrons in a quantum dot under strong magnetic field.The ground-state energy, distribution functions of density and angular momentum, and pair correlation function are calculated in the strong field limit by numerical diagonalization of the system containing up to seven electrons.It is shown that the composite fermion picture explains the small magic numbers well, while a simple geometrical picture does better as the magic number increases.Combination of these two pictures leads to identification of all the magic numbers. Relation of the magic-number states to the Wigner crystal and the fractional quantum Hall state is discussed.
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  • Ryuichi Ugajin
    Subject area: Electron states in condensed matter.
    1996 Volume 65 Issue 12 Pages 3952-3956
    Published: December 01, 1996
    Released on J-STAGE: October 01, 1999
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    An addition spectral analysis on a finite clusterfrom the double-layered lattice model, which has beenintroduced to describe quantum dot arrays under an externalelectric field perpendicular to the array, is presented.When the density of electrons is near to quarter-filled, we found a new type of Mott transition, in which themetal-insulator transition goes through a heavy-electron phase.In this new Mott transition, the Mott insulating state becomes unstablebecause Gibbs states having more pairs of electronsare favored as well as the Mott insulating state, resulting in an enhancement of electron-density fluctuation.
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  • Izumi Hase, Yoshikazu Nishihara
    Subject area: Electron states in condensed matter.
    1996 Volume 65 Issue 12 Pages 3957-3963
    Published: December 01, 1996
    Released on J-STAGE: October 01, 1999
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    The electronic energy band structures for Sr2RuO4 and Sr2RhO4, which are considered as highly correlated layered structure systems, have been calculated by using the scalar-relativistic full-potential linearized augmented plane wave (FLAPW) method within the local-density approximation. The result of the calculation suggests that both compounds are compensated metals. It is found that one of the calculated Fermi surfaces of Sr2RhO4 have three-dimensional characters.
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  • Nikolai Plakida
    Subject area: Electronic transport in condensed matter.
    1996 Volume 65 Issue 12 Pages 3964-3972
    Published: December 01, 1996
    Released on J-STAGE: October 01, 1999
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    Frequency dependent conductivity σ(ω)is calculated for the asymmetric Hubbard model in the limit ofstrong correlations, U >> |tαβ|, where tαβ are the hopping integrals for the lower (α = β =1) or the upper (α = β =2) Hubbard bands.By applying the memory function technique in terms of the Hubbard operatorsrelaxation rates due to electron scattering on spin and charge dynamicalfluctuations are calculated.A generalized Drude law for σ(ω)is obtained with essentially two contributions in the low frequencyregion (Drude part) and in the high frequency region, hω ≅ U. It is shown that the Drude relaxation rate isproportional to [(tαα)2 - (t12)2]2and goes to zero for the symmetric Hubbard model (tαβ =t)where σ(ω) ∝ δ (ω). It is suggestedthat for electronically doped copper oxides spin fluctuation relaxationrates should be much weaker then for hole doped ones.
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  • Masayuki Tanaka, Masashi Hasegawa, Humihiko Takei
    Subject area: Electronic transport in condensed matter.
    1996 Volume 65 Issue 12 Pages 3973-3977
    Published: December 01, 1996
    Released on J-STAGE: October 01, 1999
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    Single crystals of PdCoO2 have been successfully grown using the metathetical reaction. The obtained crystals have silverly metallic lustre and a well-habited hexagonal platelet shape. Anisotropic temperature dependence of the electrical resistivity and magnetic susceptibility have been first clarified. The resistivities both perpendicular and parallel to the c-axis show a metallic behavior with large anisotropy. The resistivities perpendicular to the c-axis are particularly in order of μΩcm at room temperature, which are lowest among the usual, normal state oxides.
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