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Shingo Ishiwata, Yoshiko Okada, Shinsuke Watanabe, Hiroshi Tanaca
1990 Volume 59 Issue 9 Pages
3029-3032
Published: September 15, 1990
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Soliton propagation in a random medium has been numerically studied. As a model of the system, we consider a one-dimensional Toda lattice where two different mass particles are distributed randomly but the interaction potential is uniform. It is shown that the amplitude of a soliton decreases as
n−1∼
n−1.2 (
n denotes the lattice point) in the course of propagation and that the damping is enhanced with soliton amplitude. The possibility of soliton damping with hysteresis is suggested.
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Yoshiomi Kondoh, Jia-Ling Liang, Takashi Yabe, Takeo Ishikawa, Satarou ...
1990 Volume 59 Issue 9 Pages
3033-3036
Published: September 15, 1990
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A new method to improve numerical schemes for solving hyperbolic equations is presented. In this method, multisubscales are locally opened in addition to the main-scale mesh, depending on the local magnitudes of the first and the second derivatives. Singular points such as sharp edge regions of curves are processed by using a delta functionlike treatment. Numerical results on the propagations of triangular and square waves are shown to clarify the usefulness of the method.
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Shozo Takeno, Kazunari Hori
1990 Volume 59 Issue 9 Pages
3037-3040
Published: September 15, 1990
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A pure one-dimensional lattice with quartic anharmonicity and nearest-neighbor interactions is shown to exhibit a fairly well-defined propagating self-localized mode above the harmonic frequency band. This is a propagating-mode version of a stationary, immobile p-like self-localized mode having the displacement pattern (…, 0, 0, −1⁄2, 1/2, 0, 0, …) in the extreme localization limit. An approximate analytical expression for localized-mode envelope functions is obtained in a form similar to that of the Ablowitz-Ladik lattice solitons. Nonlinear eigenvalue equations are studied by using the method of lattice Green’s functions, by which an approximate analytical expression for the dispersion relation of the localized mode is also obtained.
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Noriko Akutsu, Yasuhiro Akutsu
1990 Volume 59 Issue 9 Pages
3041-3044
Published: September 15, 1990
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We propose an efficient approximation scheme to calculate one-dimensional anisotropic interface tension γ(θ) (θ: interface orientation angle). For a given system, we set up an approximate free random-walk problem where an extra
imaginary factor e
iφ⁄2 is assigned at each turn of the walks, just as in Feynman-Vdovichenko’s random-walk solution of the Ising model. We calculate γ(θ) from the lattice Green’s function (
Remark: Graphics omitted.) associated with the random-walk problem. The equilibrium crystal shape is simply given by imaginary poles of (
Remark: Graphics omitted.). We apply the method, the
imaginary path-weight method, to the hexagonal antiferromagnetic Ising model in a uniform field. We show that, at a particular orientation, the calculated γ(θ) reproduces the accurate solid-on-solid result. The Wulff plot and the equilibrium crystal shape are presented.
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Takayuki Kamimura, Masanori Matoba, Shuichiro Anzai
1990 Volume 59 Issue 9 Pages
3045-3048
Published: September 15, 1990
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X-ray diffraction, electrical resistivity, DSC and XPS investigations were carried out on Cu
4Sn
1−xGe
xS
4 (0≤
x≤1.0). At room temperature, the orthorhombic structure changes to a monoclinic one at a transition concentration of
xt=0.6 as
x increases. This transition also exhibits the expansions in the energy width between the top of the valence band and the Fermi level and in the lattice parameter
B. The transition has the characteristics of the first-order high (high temperature)-to-low (low temperature) conductivity phase transition as reported on Cu
4SnS
4. The transition temperature
Tt linearly increases with
x. These features are briefly compared with the electronic and structural phase transition reported on SnTe and Pb
1−xGe
xTe.
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Noritaka Kuroda, Masamichi Sakai, Masashi Suezawa, Yuichiro Nishina, K ...
1990 Volume 59 Issue 9 Pages
3049-3052
Published: September 15, 1990
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On the basis of the temperature dependence of the ESR spectrum, the optically induced unpaired spins in [Pt(en)
2][Pt(en)
2Cl
2](ClO
4)
4, where en is ethylenediamine, are verified to form dimeric states of Pt ions which are mobile but transport no electric charge. The dimer hops along the …–Pt–Cl–Pt–Cl–… chain in a manner of random walk. The hopping rate is given by ν
c=ν
0 exp (−
Δ⁄
kT) with ν
0=1.3×10
9 sec
−1 and
Δ=13±1 meV over a wide temperature range from liquid He to the ambient. This state is most likely the neutral soliton.
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Hiroshi Kamimura, Mikio Eto
1990 Volume 59 Issue 9 Pages
3053-3056
Published: September 15, 1990
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By the first-principles variational calculations we show that, with the increase of Sr concentration, the ground state of CuO
6 octahedron in La
2−xSr
xCuO
4 changes from
1A
1g to
3B
1g near the observed onset concentration of superconductivity while the ground state of the CuO
4 cluster in Nd
2−xCe
xCuO
4 is always
3B
1g in the presence of dopant electrons. Based on this result, two kinds of phase diagrams are predicted for hole- and electron-doped superconductors. These results support the spin polaron mechanism proposed by Kamimura
et al.
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Hirokazu Tsunetsugu
1990 Volume 59 Issue 9 Pages
3057-3060
Published: September 15, 1990
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Stability of the Penrose lattice against the other local isomorphism classes is studied from the viewpoint of electron kinetic energy. Numerical calculations on a tight-binding Hamiltonian with up to 1364 sites indicate that the original Penrose lattice is the most stable for the electron concentration 0<ν<0.082 and 0.112<ν<0.540. This stability is explained in terms of the ring statistics of the lattice. Some features of the energy spectrum, energy gaps and degeneracy of the confined/string states, are also discussed.
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Teruya Shinjo, Hidefumi Yamamoto
1990 Volume 59 Issue 9 Pages
3061-3064
Published: September 15, 1990
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Multilayers consisting of two magnetic components with different anisotropies were prepared by successively depositing Co, Cu, Ni
80Fe
20 and Cu layers. By applying a moderate field, the two magnetizations are oriented antiparallel with each other, and then the electric resistance significantly increases due to spin-dependent electron scattering. A large magnetoresistance change, 9.9% at 300 K, was observed in [Co(30 Å)/Cu(50 Å)/NiFe(30 Å)/Cu(50 Å)]×15.
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Hideo Yoshioka, Hidetoshi Fukuyama
1990 Volume 59 Issue 9 Pages
3065-3068
Published: September 15, 1990
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The Josephson current induced by the proximity effect is calculated for a structure with a mesoscopic ring. The result shows that the phase of superconductors and that of mesoscopic systems are entangled and the maximum current is a periodic function of the magnetic flux through the ring.
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Ryuta Yagi, Yasuhiro Iye, Toshihito Osada, Seiichi Kagoshima
1990 Volume 59 Issue 9 Pages
3069-3072
Published: September 15, 1990
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In an attempt to understand angular-dependent oscillatory magnetoresistance phenomena recently discovered in organic conductors, calculations of magnetoresistance in quasi-two-dimensional systems were carried out in the framework of the Boltzmann transport theory. Calculated magnetoresistance curves show the angular-dependent oscillations reminiscent of those found experimentally. It is argued that the essential physics underlying the resistance oscillations lies in the angular dependence of the high field asymptotic behavior (saturation
vs divergence) of semiclassical magnetoresistance which arises from Fermi surface topology.
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Kazuyoshi Yoshimura, Youichi Nishizawa, Yutaka Ueda, Koji Kosuge
1990 Volume 59 Issue 9 Pages
3073-3076
Published: September 15, 1990
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The ac susceptibility was measured for the powdered samples of La
2−xSr
xCuO
y with various Sr and oxygen contents. Only the sample with a composition of
x∼0.16 and
y∼4.0 shows a sharp superconducting transition at 38 K having the maximum value of the Meissner volume fraction
f of more than 80% of the ideal value. The samples with the other concentrations have broad transitions at lower transition temperatures with smaller
f, while the onset temperature of the Meissner effect was observed to be independent of
x and
y, and close to 38 K, suggesting that only the compound with
x∼0.16 and
y∼4.0 shows intrinsic superconductivity in this system.
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Susamu Taketomi, Nobuyuki Inaba, Hiromasa Takahashi, Hideki Miyajima
1990 Volume 59 Issue 9 Pages
3077-3080
Published: September 15, 1990
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The magnetic-field,
H, dependence of the magnetic birefringence of two kinds of magnetic fluid thin-film samples was measured in a region with a low magnetic field of less than 150 Oe. While the magnetic fluid of one sample had been exposed in a vacuum state for several minutes before the optical measurement, that of the other had not. The birefringence
Δn of the former sample is proportional to
H2, but
Δn of the latter is in proportion to
H in the low-field region. The magnetic birefringence of the former sample is attributed to the interaction between an individual magnetic colloidal particle and the external field, but that of the latter is due to the interaction among the colloidal particles exerted by the field.
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Kinshiro Hirakawa, Ray Osborn, Andrew D. Taylor, Kaoru Takeda
1990 Volume 59 Issue 9 Pages
3081-3084
Published: September 15, 1990
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LiNiO
2 has been pointed out as a candidate for the model substance of
S=1⁄2 triangular antiferromagnet with Ising-like interaction whose ground state would be a spin quantum liquid as proposed by Fazekas and Anderson. In order to see the nature of the excitation spectrum, a pulse neutron scattering study was performed, and a strong inelastic diffuse scattering has been observed instead of the antiferromagnetic Bragg scattering.
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Masato Nakamura, Toshimichi Yasuda
1990 Volume 59 Issue 9 Pages
3085-3088
Published: September 15, 1990
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We investigate the spin depolarization of a classical particle performing random walk on a linear chain with Larmor frequencies arranged in Fibonacci sequence. This model may correspond to muon spin depolarization in a quasicrystal at high temperature. We compare the result with those for alternating and random arrangements of Larmor frequencies.
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Hirohito Fukutani, Akio Yamada, Kazutoshi Yagi, Satoshi Ooe, Kazuyuki ...
1990 Volume 59 Issue 9 Pages
3089-3092
Published: September 15, 1990
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Neutron-irradiated graphites were studied by reflectivity and photoemission (UPS, ARUPS, XPS) measurements. The π-band reflectivity peak of graphite, located at 5 eV, changed significantly and a small absorption band ascribed to vacancies produced by neutron bombardment was found to grow around 3 eV. Modification of the valence band by neutron irradiation was studied by ARUPS. The π-valence band shifts to lower binding energy towards the Fermi level and its band width becomes smaller. These results were also confirmed by the optical joint density of states obtained from K–K analysis of the reflectivity.
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Yoshimasa Matsuno
1990 Volume 59 Issue 9 Pages
3093-3100
Published: September 15, 1990
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A systematic method is developed for evaluating conservation laws of nonlinear evolution equations (NEE’s) by employing the time parts of the Bäcklund transformations. The properties of conservation laws are then investigated in detail to obtain the informations about the structure of NEE’s themselves. In particular, we focus our attention on the independence of conservation laws. The NEE’s considered in this paper are the Boussinesq equation, a model equation for shallow-water waves due to Hirota and Satsuma, the Sawada-Kotera and the Kaup equations and the Ito equation. For all these equations, the inverse scattering transform problems have not been fully solved since the associated isospectral equations become higher-order ones in comparison with the usual Schrödinger equation.
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Akira Nakamura
1990 Volume 59 Issue 9 Pages
3101-3111
Published: September 15, 1990
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We consider the 2+1 dimensional Toda Molecule equation
Δ log
Vn−
Vn+1+2
Vn−
Vn−1=0 where
Δ≡(∂⁄∂
x)
2+(∂⁄∂
y)
2. The boundary condition is molecule type, which is
Vn=0 at finite
n corresponding to both ends of the molecule. Recently we reported the existence of the Toda Molecule cylindrical solitons which have smooth connection to the Toda Lattice cylindrical solitons in the large molecule limit and are expressed by the associated Legendre functions. We have found that such cylindrical solitons can be generalized further by the use of Jacobi polynomials.
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Yuji Nakawaki
1990 Volume 59 Issue 9 Pages
3112-3126
Published: September 15, 1990
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To complete solving the nonlinear Schrödinger model by means of the quantum inverse scattering method, we realize scattering data operators including those for bound states in terms of reflection coefficient operators in the framework of the inverse problem. To this end, we formulate quantum Gel’fand-Levitan equations for Jost solutions of generalized Zakharov-Shabat eigenvalue problems. Our formulation becomes simpler and clearer than that of Göckeler because we fully use the newly found fact that in the similar manner as the classical case one of Jost solutions can be described in terms of linearly independent ones for each
n (
n=1, 2, 3, …). We also verify operator identities among Jost solutions for each
n which are indispensable to express discontinuities of piecewise analytic operators in such a way that we obtain closed Gel’fand-Levitan equations.
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Shozo Takeno
1990 Volume 59 Issue 9 Pages
3127-3141
Published: September 15, 1990
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A quantum theory of dynamical self-trapping in a quasi-one-dimensional (1d) lattice of vibrons by phonons is presented to explore possible existence of soliton-like entities in α-helical proteins and related model dynamical 1d lattices. The theory developed here distinguishes itself from others based on the Fröhlich-type Hamiltonian and the use of the continuum approximation in the following two respects: (1) By virtue of the number-nonconserving nature of vibrons, coherent states can be taken as a natural basis for studying a soliton-like state in quantum mechanics. (2) A self-localized mode, movable or stationary, appearing below the bottom of the frequency band of phonon-free vibrons can be identified as a soliton in the lattice system. To solve integro-differential-difference equations, an adiabatic approximation and the lattice-Green’s functions are used.
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Tsuyoshi Horiguchi
1990 Volume 59 Issue 9 Pages
3142-3147
Published: September 15, 1990
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We investigate the low-temperature behaviors of the spin-pair correlation functions at large distances, the correlation length and the zero-field susceptibility for the infinite-spin Ising model in a one-dimensional lattice. By solving an integral equation, we find that the divergent behavior of the correlation length is weaker than the one for the finite-spin Ising models.
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Wei Guo Jin, Takayoshi Horiguchi, Masanori Wakasugi, Yasukazu Yoshizaw ...
1990 Volume 59 Issue 9 Pages
3148-3154
Published: September 15, 1990
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Isotope shifts of 5 transitions from the
3H6 and
3F4 levels of the ground configuration 4
f126
s2 in Er I were measured for the stable isotopes with
A=162–170 by the atomic-beam laser spectroscopy. Hyperfine constants
A and
B of 7 atomic levels were determined. Changes of mean square nuclear charge radii δ〈
r2〉 and mean square nuclear deformation parameters δ〈β
2〉 were deduced. The deformations of
164−170Er were found to be mainly quadrupole and contributions of higher order deformation parameters for
162Er were estimated.
J-dependence of isotope shifts in the (6, 1) term of 4
f126
s6
p was found. It is concluded that the
J-dependence was caused by the crossed-second-order effect in which the field shift has dominant contribution.
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S. Chang, B. M. Garraway, V. G. Minogin
1990 Volume 59 Issue 9 Pages
3155-3166
Published: September 15, 1990
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We examine the dynamics of five-level atoms interacting with two standing waves. In our approach we describe the motion of the atoms by a Fokker-Planck equation, including the effect of velocity-dependent two-photon Raman processes within the second order rate equation approximation. By using this procedure we numerically calculate the cooled temperatures of sodium atoms. We then find two principal types of behaviour; that of two-level and three-level atomic systems. We are also able to find detunings of the standing waves for which the atoms are cooled to temperatures below the “Doppler limit”.
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Katsumi Takenouchi, Zhipo Tang
1990 Volume 59 Issue 9 Pages
3167-3181
Published: September 15, 1990
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The two-dimensional magnetohydrodynamic flow is investigated, in which the applied magnetic field is produced by an electric current perpendicular to the main flow whose speed is supersonic. The equations are linearlized assuming that the magnetic Reynolds number and the interaction parameter are small, and the solutions are obtained by means of the bilateral Laplace transform. The numerical results show that the flow is decelerated almost over the flow region, and that downstream of the current position remarkably oscillatory variations occur in the retarded flow. These features of supersonic flow are particularly of interest as compared with the subsonic case.
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Takeshi Iizuka, Miki Wadati
1990 Volume 59 Issue 9 Pages
3182-3193
Published: September 15, 1990
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A nonlinear stage of the two-dimensional Rayleigh-Taylor instability is studied by including the effect of surface tension between the two fluids. By means of the reductive perturbation method, three types of nonlinear evolution equations for the interface are obtained. Each equation is valid within a certain region of the wave number
k introduced in the linearized theory. When
k is sufficiently large and thus in the stable region, the nonlinear Schrödinger equation is derived. Depending on the value of
k in this region, bright or dark solitons exist. When
k is nearly equal to the critical wave number
kc, the unstable nonlinear Schrödinger equation is obtained. Further, it is shown that a nonlinear diffusion equation is obtained in the unstable region where
k is smaller than
kc.
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Jae-Tack Jeong, Moon-Uhn Kim
1990 Volume 59 Issue 9 Pages
3194-3202
Published: September 15, 1990
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Two problems on the two-dimensional slow viscous flow due to the rotation of a body with cusped edges are considered on the basis of the Stokes approximation. An exact formal expression for the flow produced by the rotation of a star-shaped body composed of finite hinged plates of equal length and angular separation is obtained by use of the Wiener-Hopf technique. And an explicit expression for the flow due to the rotation of a hypocycloid is given. Special attention is paid to the flow near the protruding cusped edge for each case. The torque exerted on the body is also calculated.
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Keiichi Kondo, Nobuaki Ikuta
1990 Volume 59 Issue 9 Pages
3203-3216
Published: September 15, 1990
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Rotational temperature rise of N
2 molecules in the repetitive positive streamer corona in a point to plane gap in air under DC voltage is measured with high resolution in space and time. In the pair of the successive luminous waves in each stramer, the gas temperature rise of a few hundred degrees is observed only in the secondary wave over its luminous period. The gas temperature rise in such a small level seems to bring small effect on the sparkover of the whole gap following to the secondary wave. The mechanisms of the gas heating and cooling, the development of primary and secondary waves and of the whole gap sparkover are discussed.
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Shigehiko Nonaka
1990 Volume 59 Issue 9 Pages
3217-3226
Published: September 15, 1990
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Fundamental solutions for radio frequency (RF) discharges between parallel-plate electrodes were obtained theoretically using a quasi-static linear Laplace equation, in particular, the produced plasma density and the minimum RF threshold voltage for maintaining the plasma. In this theory, the plasma was assumed to be uniformly produced between electrodes, and each electrode was completely covered by a dielectric. The theory shows that the mechanism for RF discharges arises from a geometrical resonance of electron plasma oscillation. The phase and amplitude properties for electric field in plasma were also deduced qualitatively from this theory. This theory may be applicable for wide ranges of gas pressure and RF frequency.
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Reiji Sugaya
1990 Volume 59 Issue 9 Pages
3227-3236
Published: September 15, 1990
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Nonlinear absorption due to nonlinear Landau damping of lower-hybrid waves is investigated theoretically by analyzing the kinetic wave equations which describe nonlinear Landau damping of electrostatic waves propagating almost perpendicularly to the magnetic field. It is shown that nonlinear ion-cyclotron damping can cause a nonlinear absorption by bulk ions at ω⁄ω
1h\lesssim1.2∼1.5, and nonlinear electron Landau damping can cause an efficient nonlinear absorption by bulk electrons at ω⁄ω
1h\gtrsim1.5∼2. The former nonlinear absorption depends on
k⊥ρ
i and weakly depends on the electron temperature. The latter depends on the electron temperature strongly.
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Tetsu Yajima, Miki Wadati
1990 Volume 59 Issue 9 Pages
3237-3248
Published: September 15, 1990
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In order to investigate soliton phenomena in electron beam plasma, the unstable nonlinear Schrödinger equation i
qx+
qtt+2|
q|
2q=0 is studied. By the inverse scattering method, initial value problem is solved for a class of decreasing functions. Two special initial conditions are examined in detail. Based on the results, properties and roles of solitons in unstable nonlinear systems are discussed. Further, a recent experiment on nonlinear waves in electron beam plasma is explained.
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Yukio Noda, Hirofumi Kasatani, Yukiho Watanabe, Hikaru Terauchi, Kazuo ...
1990 Volume 59 Issue 9 Pages
3249-3253
Published: September 15, 1990
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Structure analysis of K
3D(SO
4)
2 was performed by X-ray diffraction at room temperature. Cell parameters were obtained as
a=9.787(3) Å,
b=5.682(2) Å,
c=14.697(4) Å, β=103.00(2)° with a space group
A2⁄
a,
Z=4. Excess electrons were found on a differential Fourier map around a center of inversion. The structure is isomorphous to that of K
3H(SO
4)
2 reported by Noda
et al., and the deuterium atoms take the disordered state at room temperature. Obtained hydrogen bond character such as
ROO=2.519(2) Å and
RDD=0.66(8) Å were compared with those of K
3H(SO
4)
2 in connection with a geometrical isotope effect.
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Haruyuki Mori, Kozo Hoshino, Mitsuo Watabe
1990 Volume 59 Issue 9 Pages
3254-3259
Published: September 15, 1990
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The density dependence of the structure of liquid Cs expanded along the liquid-vapour coexistence curve is studied by the molecular dynamics (MD) simulation based on the effective pair potential calculated by the pseudopotential theory. The obtained pair correlation functions are compared with the recent neutron diffraction experiment due to Winter
et al. and with the theoretical results in the modified hypernetted-chain (MHNC) approximation. It is shown that the characteristic features of the density dependence of the MD results agree well with the experimental ones and that the MD results are in excellent agreement with the MHNC results. The characteristic features of the atomic arrangements are also investigated by using the Voronoi tessellation.
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Yoshiko H. Ohashi, Kazutoshi Ohashi, Mitsuru Fukuchi
1990 Volume 59 Issue 9 Pages
3260-3268
Published: September 15, 1990
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Depinning process of a dislocation from an obstacle has been investigated by using the method of computer simulation. The motion of a dislocation is analyzed by using the Frenkel-Kontorova model in which both effects of an impurity atom and temperature are included. When an impurity atom shows strong effect on a dislocation, the dislocation may be trapped by the defect. But, with increasing temperature, the dislocation may be escaped from the defect with the help of thermal phonon. When this depinning process occurs in the lower temperature region, the dislocation climbs the defect potential well with extending its core size. On the other hand, when the depinning process occurs in the high temperature region, the oscillating dislocation can climb the well just as a classical particle because of its large kinetic energy.
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Yasusada Yamada
1990 Volume 59 Issue 9 Pages
3269-3275
Published: September 15, 1990
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The successive phase transition scheme in VRu alloy has been discussed based on Ginzburg-Landau type phenomenological treatment. The intrinsic soft mode in this material is assumed to be on the [110]-direction as usually happens in various bcc-based marten-sites. The particular incommensurate phase with an off-symmetric modulation wave vector is characterized to be a ‘partially incommensurate’ (PIC) phase in which only one component of the wave vector of the intrinsic soft mode selectively locks into the commensurate value. It is noticed that the partial lock-in is a characteristic feature of the multiple-Q state stabilization. It is also noticed that due to the coupling between the modulation waves and bulk strain, the PIC phase completely overrides the IC phase, whence the transition proceeds as N→PIC→C in consistent with the experimental results.
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Doan Nhat Quang
1990 Volume 59 Issue 9 Pages
3276-3283
Published: September 15, 1990
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A theory is developed of the Auger recombination occurring in a piezoelectric semiconductor propagated by an intense acoustic noise flux. The calculation of the Auger coefficient is carried out within the classical approach to the piezoelectric noise field and for the case of nondegenerate carrier statistics. Then a simple analytic expression of the Auger coefficient is derived, which exhibits a linearly exponential function of the flux intensity. The screening effect of charge carriers is shown to be of great importance. The Auger recombination is found to be strongly enhanced as compared to that in the appropriate noiseless sample up to several orders of magnitude at large flux intensity, low temperature and small carrier concentration. Thus this gives another example illustrating the earlier statement that the Auger transition might still be one of the leading recombination mechanisms for disordered systems.
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Kouki Yamamoto, Kazuo Ueda
1990 Volume 59 Issue 9 Pages
3284-3288
Published: September 15, 1990
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The exact numerical diagonalization of the 1-D Kondo lattice is done to obtain energies and correlation functions of this system. In this system the ground state changes from a ferromagnetic state in the low density limit of conduction electrons to a total spin singlet state for the half-filled conduction band. The main mechanism for the suppression of the total spin for half-filling is the antiferromagnetic correlation between the localized spins of nearest neighbor sites. However, the comparison of energies show that the Kondo effect also plays an important role. Increasing the magnetization of the 1-D Kondo lattice the system changes its nature and behaves as a simple spin system, which is determined only by the RKKY interaction.
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Tsuyoshi Yamaguchi, Nobuhisa Fujima
1990 Volume 59 Issue 9 Pages
3289-3298
Published: September 15, 1990
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Electronic states are calculated by the DV–Xα method for (i) the planar octahedron cluster Cu
4O
20, (ii) the planar pyramid cluster Cu
4O
16, (iii) the planar square cluster Cu
4O
12, and (iv) the linear square cluster Cu
4O
13, in the high
TC superconductor oxides. The calculation is performed for cases where the cluster is completely ionic and where a single hole or electron is doped. The hole doped in the Cu
4O
20 cluster stays in the Cu–O basal plane and does not stay at the apex O site. The hole or electron doped in the remaining three clusters stays over the whole cluster. It is important to take into account of Madelung energy in the calculation of electronic states of clusters cut out from crystals.
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Katsuhiko Takegahara, Tadao Kasuya
1990 Volume 59 Issue 9 Pages
3299-3306
Published: September 15, 1990
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One-electron energy band structure for LuInCu
4, which is a proper reference material for the study of the valence transition in YbInCu
4, is calculated by a self-consistent APW method with the local density approximation. The calculated result shows that the compound is the semimetal. This property is consistent with the observed unusual behavior. In order to estimate the mixing term between the 4
f electron and the valence and conduction electrons, the energy band structure for YbInCu
4 is also calculated. The obtained result is followings; (
pfσ)=0.27 eV for Yb 4
f and Cu
p states and (
dfσ)=−0.14 eV for Lu 4
f and Cu 3
d states. These values are nearly same order as those of Ce compounds.
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Kosai Tanabe, Mitsuru Ogoshi
1990 Volume 59 Issue 9 Pages
3307-3321
Published: September 15, 1990
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To describe comprehensively the superconducting phase together with the other phases realized in the copper oxcides, the normal phase, the antiferro-magnetic and the spin-glass phases, an application of the constrained thermal Hartree-Fock-Bogoliubov (CTHFB) approximation is proposed. A set of the electron number- and the magnetization-constrained formalism is exemplified by employing the one-band Hubbard model. The CTHFB equation is applicable to the microscopic interaction whether it includes the phonon-mediated pairing interaction, or it provides a self-sustaining mechanism of the Cooper pair formation. A new type of the order parameter is introduced by extending the generalized Bogoliubov transformation to mix electron spin projections onto the quantization axis (i.e. \hat
Sz). This yields the lowered minimum of the grand potential, which corresponds to the physical solution violating time-reversal invariance. The gradient method is proposed to solve the CTHFB equation, the non-linear eigenvalue broblem with constraints.
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Takehiko Oguchi, Hidetsugu Kitatani
1990 Volume 59 Issue 9 Pages
3322-3330
Published: September 15, 1990
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A spin wave theory for a frustrated antiferromagnetic Heisenberg model on a square lattice is developed using spin operators introduced by Oguchi and Honma. Exchange integrals between nearest neighbor and next nearest neighbor are denoted by
J1=
pJ and
J2=(1−
p)
J where 0≤
p≤1, and
J is a positive constant. Since the ground state for 0≤
p≤1⁄3 is different from that for 1⁄3≤
p≤1, they are treated separately. The energy, staggered magnetization and correlation functions in the ground state are calculated over the whole range of
p. For the special case of
p=0, they are compared with Takahashi’s theory. Furthermore, direct calculations for finite lattice with 16 and 20 spins are shown for reference.
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Kiyohiro Sugiyama, Hiroyuki Fuke, Koichi Kindo, Kenji Shimohata, Alois ...
1990 Volume 59 Issue 9 Pages
3331-3339
Published: September 15, 1990
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High-field magnetization and magnetoresistance of URu
2Si
2 single crystal are investigated up to 600 kOe. Three-step metamagnetic transitions are obtained with the transition fields of 358, 365 and 396 kOe at 1.3 K. The experimental results are explained quantitatively by introducing the model that the heavy Fermion state produced by the mixing of the f- and conduction electrons is destroyed by applying the field and that the exchange interactions between the recovered local f-electron magnetic moments on the uranium atom play an important role on the magnetic properties at high field. The frustration due to the exchange interactions induces the three-step metamagnetic transitions.
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Keiichi Ohara, Kei Yosida
1990 Volume 59 Issue 9 Pages
3340-3344
Published: September 15, 1990
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In the modified spin-wave theory for square-lattice antiferromagnets developed in a previous paper, the susceptibility was calculated analytically in the low temperature limit. In this paper, the susceptibility and the specific heat are calculated numerically over the whole temperature range and compared with those obtained by high-temperature expansion. The correlation length is also calculated numerically as a function of temperature.
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Katsurou Hanzawa, Fujihiko Komatsu, Kei Yosida
1990 Volume 59 Issue 9 Pages
3345-3350
Published: September 15, 1990
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A consistent explanation of the electric field gradients at Cu and O nuclei in YBa
2Cu
3O
7 is obtained provided that on-site 3
d and 2
p holes give the dominant contributions. The number of holes per Cu(2) site in the planer
dx2−y2-
pσ antibonding orbital is estimated to be nearly one (that is, the orbital is nearly half-filled), more than half of which are attributed to the oxygen 2
p holes. For oxygen sites, it is necessary to consider both the
pσ and
pπ holes, while more than 80% of 2
p holes reside on the
pσ orbitals in all oxygen sites.
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Ryuji Abe, Masakiyo Horioka, Izumi Sakumiya, Tadaaki Nakagawa
1990 Volume 59 Issue 9 Pages
3351-3357
Published: September 15, 1990
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The dielectric dispersion and nuclear magnetic relaxation of glycerol-water and glycerol-deuterium oxide mixtures have been measured in the range from room temperature to liquid nitrogen temperature. The Cole-Cole plots of both glycerol-water and glycerol-deuterium oxide mixtures can be well represented by the Williams-Watts description. The parameter β appearing in the description becomes a definite value with approaching the glass transition temperature
T0. The temperature dependence of the relaxation time for both glycerol-water and glycerol-deuterium oxide mixtures can be well represented by the Vogel-Tamman-Fulcher law. Both the parameters,
B and
T0, appearing in the relation decreases with decreasing contents of glycerol, but
B⁄
T0 remains constant. These results are discussed by the idea of hierarchically constrained dynamics proposed by Palmer
et al.
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Shin Imada, Takeo Jo
1990 Volume 59 Issue 9 Pages
3358-3373
Published: September 15, 1990
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We present a calculation of magnetic circular dichroism in 3
d and 4
d core X-ray absorption spectra of rare earth systems assuming that a trivalent rare earth ion is placed in an infinitesimal uniform magnetic field. The calculation covers all rare earth elements between Ce and Tm. Features of the dichroism are explained by elementary considerations of transition matrix of a polarized light, spin-orbit coupling of a core hole, and exchange interaction between a core hole and a 4
f electron.
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Satoshi Sasaki, Noboru Miura, Yoshiji Horikoshi
1990 Volume 59 Issue 9 Pages
3374-3387
Published: September 15, 1990
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Magneto-optical spectra of the type I(GaAs)
m/(Al
xGa
1−xAs)
n (
x\simeq0.5) short period superlattices have been investigated in pulsed high magnetic fields up to 40 T. In two samples with (
m,
n)=(6, 6) and (7, 5), formation of fairly wide minibands in the perpendicular direction to the layers resulted in only small anisotropy in observed reduced masses of electrons and holes with respect to field configuration, and small binding energy of heavy hole excitons. Calculations of magnetic energy levels were conducted within the frame work of envelope function formalism for magnetic field parallel to the layers. The calculated results were found to be in excellent agreement with the experimental results, implying the validity of the effective mass approximation for these values of
m and
n.
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Shin-ichi Kimura, Takao Nanba, Satoru Kunii, Tadao Kasuya
1990 Volume 59 Issue 9 Pages
3388-3392
Published: September 15, 1990
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Optical conductivity spectra of rare-earth hexaboride crystals (ReB
6: Re=La, Ce, Pr, Nd, Sm, Eu and Gd) were obtained by the Kramers-Kronig transformation of the reflectivity spectra measured in the photon energy from 1 meV to 25 eV. The majority of the structures in these spectra were assigned to originate from the optical interband transition from the bonding Boron 2
p bands to the anti-bonding Boron 2
p bands. The main 5
d band was assigned to be about 5 eV above the Fermi level. The peaks at about 14 eV for SmB
6, 15 eV for GdB
6 and 9 eV for EuB
6 were assigned to be the transition from the 4
f states to the 5
d band. The oscillator strength of this 4
f-5
d transition was estimated to be 0.57∼0.67 for SmB
6 and 0.54 for GdB
6.
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Hideo Suzuki, Keisho Umezaki, Tohru Sugimoto
1990 Volume 59 Issue 9 Pages
3393-3400
Published: September 15, 1990
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The interaction of formamide with the external electric field produced by a unit point-charge moving in one direction at a constant velocity is calculated according to our extended INDO–CI method for valence-shell electrons and the perturbation theory for degenerate states. Also, the change in the net-charges on atoms in formamide caused by the interaction is examined, together with the change in the internal electric field produced at the position of the point-charge by the net-charge distribution in formamide. It is thus shown that the interaction between formamide and the point-charge exerts a considerable influence not only on the net-charge distribution in formamide but also on the internal electric field acting on the point-charge.
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Ichiro Aoki
1990 Volume 59 Issue 9 Pages
3401-3407
Published: September 15, 1990
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A system-theoretical approach, the input-output flow analysis, is applied to the study of water flow, protein metabolism and energy flow in human body: indices characterizing patterns of flow, that is, throughflow, total system throughflow, path length, cycling index and trophic position are calculated and discussed for flow-networks within human body. Cycling indices for energy-flow are zero and those for mass-flow are large; this tendency is also the case for ecosystems as systems-ecology shows. In this respect, a human body can be regarded as a “mini-ecosystem”. Trophic positions for mass-flow are larger than the numberings of compartment, showing also quantitatively the existence of intense cycling in mass-flow in human body.
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Riki Kawashima, Hiroshi Isoda
1990 Volume 59 Issue 9 Pages
3408-3409
Published: September 15, 1990
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