-
Jian–Xin Zhu, Z. D. Wang
Subject area: Statistical physics and thermodynamics.
1995 Volume 64 Issue 2 Pages
335-338
Published: February 01, 1995
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Based upon a tight-binding model Hamiltonian and by applying the Jordan-Wigner transformation, the Aharonov-Bohm (AB) effect for charged hard-core bosons in one-dimensional (1D) mesoscopic rings is investigated for the first time. By introducing a specific unitary transformation, the energy spectrum and the persistent charge current are analytically derived for 1D perfect lattices. Similar to electron systems, it has been found that the energy and persistent current are periodic in AB flux with the period {Φ}
0=hc/q. More interestingly, we have exactly shown that, in the absence of the external AB flux, the charge current can be self-sustained via the AB effect, which is in fact the ground state of the system regardless of the number of hard-core bosons being even or odd.
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Hiroyasu Ejiri, Ken–ichi Fushimi, Ryuta Hazama, Michio Kawasaki, ...
Subject area: Nuclear decay and radioactivity.
1995 Volume 64 Issue 2 Pages
339-343
Published: February 01, 1995
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Double beta decays (β β ) from the 0
+ ground state in
116Cd to the 0
+ ground state in
116Sn were studied by means of ELEGANT V. A finite half-life for the two-neutrino ββ (2νββ ) and an upper limit on the neutrinoless one (0νββ) were obtained as T
2ν 1/2=2.6
+0.9-0.5× 10
19, y and T
0ν 1/2>6.3× 10
21, y (68\The nuclear matrix element M
2ν ββ was deduced as 0.069± 0.009 in units of (m
ec
2)
-1. This supports the universal quenching of the 2νββ rates in this mass region, which is consistent with that previously measured in
100Mo.
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Shuji Munejiri, Fuyuki Shimojo, Kozo Hoshino, Mitsuo Watabe
Subject area: Structure of liquids and solids; crystallography.
1995 Volume 64 Issue 2 Pages
344-347
Published: February 01, 1995
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We have derived the effective pair potential of liquid sodium at 373, K from the experimental structural data using the inverse method proposed by Reatto et al. (Phys. Rev. A 33 (1986) 3451) and shown that, to improve the accuracy and the efficiency of the method, it is necessary to obtain an accurate pair distribution function by performing the simulation for a large system with the pair potential truncated at a large cutoff distance and by extrapolating it carefully.
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Jun–ichiro Suda, Mitsugu Matsushita
Subject area: Structure of liquids and solids; crystallography.
1995 Volume 64 Issue 2 Pages
348-351
Published: February 01, 1995
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Huge spiral crystals of potassium dichromate (K
2Cr
2O
7)have been found to grow three-dimensionally in a gelatin medium when gelatincontaining K
2Cr
2O
7 was dried slowly in a test tube at a lowtemperature.These spirals were all right-handed, and their widths, axial pitches andlengths were 2--3, mm, 5--6, mm and 20--25, mm, respectively. When the gelatinconcentration in the medium was decreased, ordinary platelike crystals were observed to grow, instead of the spiral crystals. To the best of our knowledge, inorganiccompounds such as K
2Cr
2O
7 have so far not been reported toform such huge spiral crystals.It is conjectured that collagen molecules, which compose the gelatinmedium and have right-handed triple helix structure lead to the growth of spiralcrystals.
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Takashi Nagatani, Tadachika Seno
1995 Volume 64 Issue 2 Pages
352-355
Published: February 01, 1995
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Morphological changes induced by drift in the diffusion-limited aggregation (DLA) is investigated by using the experimental method of electrodeless reduction of silver ions from a AgNO
3 aqueous solution. The silver metal is grown around the electrodeless copper deposition plate within Hele-Shaw cell under an applied electric field which is induced by the electrodes positioned outside Hele-Shaw cell. The applied electric field induces drifts on the diffusive motion of silver ions. The growth pattern of the silver metal on the circular deposition plate is studied by varying strength of the applied electric field. The characteristic growth patterns appear due to the drift of silver ions. The growth-rate distribution around the circular deposition plate is determined experimentally. It is found that the drift-induced transition between growing and no growing phases occurs at a position on the circular plate.
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I. Bâldea, L. S. Cederbaum, H. Köppel
Subject area: Electron states in condensed matter.
1995 Volume 64 Issue 2 Pages
356-359
Published: February 01, 1995
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A simple analytical analysis shows that, contrary to what has been known to date, individual CDW pinning can occur even for small values of the Fukuyama-Lee-Rice parameter. The present analytical results provide a new explanation for some puzzling numerical simulation results on CDW. A test is proposed to determine the pinning nature by further numerical simulations.
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Ren–ichi Yamada, Shun–ichi Kobayashi
Subject area: Electronic transport in condensed matter.
1995 Volume 64 Issue 2 Pages
360-362
Published: February 01, 1995
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We measured the low-temperature resistance of two-dimensional random networks of very small tunneling junctions. The networks consist of slightly oxidized tin particles with linear size of about 0.1, μ m. The temperature dependence of the resistance was found to be stronger than that of the Arrhenius type within a certain temperature range. We interpret this behavior as a precursor of the charge Kosterlitz-Thouless-Berezinskii transition. The real transition is not attainable because the system is not ideally two-dimensional.
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Teruo Ono, Teruya Shinjo
Subject area: Electronic transport in condensed matter.
1995 Volume 64 Issue 2 Pages
363-366
Published: February 01, 1995
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A new class of multilayers was prepared by using substrates with V-groove micro-structures. The magnetoresistance ratio of a sample [Cu(58, Å)/Co(12, Å)/Cu(58, Å)/NiFe(12, Å)]× 180 fabricated on a substrate with a V-groove period of 2, μ m shows a large anisotropy; 12⊥endicular to the grooves and 8.1→ the grooves at room temperature.
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Atsushi Goto, Hiroshi Yasuoka, Kenji Otzschi, Yutaka Ueda
Subject area: Superconductivity.
1995 Volume 64 Issue 2 Pages
367-370
Published: February 01, 1995
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The carrier-concentration dependence of the pseudo spin gap behaviors in the optimum and the overdoped regions of the LaBa
2Cu
3O
y system has been studied by NMR. In the temperature dependences of 1/T
1T, it was observed that the spin gap behavior, which is known to exist in the underdoped region, is suppressed in the overdoped region. This seems to confirm the expectation that the spin gap behavior is specific to the underdoped region. However, LaBa
2Cu
3O
6.96, which has T
c as high as 95, K, still exhibits a clear spin-gap-like behavior. This fact suggests that the optimum hole concentration to maximize T
c does not necessarily coincide with that where the spin gap behavior disappears in this system.
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Shigemasa Matsuo, Hiroshi Shimahara, Katsuhiko Nagai
Subject area: Superconductivity.
1995 Volume 64 Issue 2 Pages
371-274
Published: February 01, 1995
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We consider a model d-wave superconductor in which the Y
2± 2 states have the highest transition temperature and the Y
2± 1 states have a slightly lower transition temperature and show that this model has a nonuniform phase just below the upper critical field in a wide temperature range. The nonuniform state is due to the mixing between the Y
2, ± 2 state and the Y
2, ± 1 state under magnetic field and has a spatially oscillating order parameter like the Fulde-Ferrell state but has a different character from the Fulde-Ferrell state because this nonuniform state is induced by the orbital magnetic effect. The relevance of the model to a heavy Fermion superconductor UPd
2Al
3 is mentioned.
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Ryuta Yagi, Shun–ichi Kobayashi
Subject area: Superconductivity.
1995 Volume 64 Issue 2 Pages
375-377
Published: February 01, 1995
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We have observed the breaking of charge-vortex duality (symmetry) in small Josephson junction arrays with finite widths. The symmetry is broken because of the difference in the sign of their image potential at the edges of the arrays. We show that the critical tunneling resistance for superconductor-insulator transition of the Josephson junction arrays depends on the width.
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Akiko Ishiguro, Anju Sawada, Yoshihiko Inada, Junko Kimura, Michiro Su ...
Subject area: Superconductivity.
1995 Volume 64 Issue 2 Pages
378-382
Published: February 01, 1995
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The ac susceptibility of the heavy fermion superconductor UPd
2Al
3 has been measured. The peak of the susceptibility has been observed in the vicinity of the upper critical field. This anomaly is explained by the flux pinning rather than by the Fulde-Ferrell state.
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Rikio Settai, Melike Abliz, Parhat Ahmet, Kazuyuki Motoki, Noriaki Kim ...
Subject area: Magnetic properties and materials.
1995 Volume 64 Issue 2 Pages
383-386
Published: February 01, 1995
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We have observed a metamagnetic transition in PrCu
2 where a cooperative Jahn-Teller effect occurs below 8, K. This transition brings about a conversion between an easy and a hard axes in magnetization, which is reflected in a drastic change of the de Haas-van Alphen amplitude, that is a change of the scattering lifetime of conduction electrons. The origin of the metamagnetic transition is ascribed to a quadrupole moment of the 4f level.
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Naoya Takeda, Jiro Kitagawa, Masayasu Ishikawa
Subject area: Magnetic properties and materials.
1995 Volume 64 Issue 2 Pages
387-390
Published: February 01, 1995
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Magnetic and transport properties of the ternary compoundCe
3Pd
20Si
6 are investigated down to 0.035, K.The temperature dependence of the electrical resistivity indicatesthat this compound is a new Kondo material. Thelow-temperature specific heat measurement reveals that C/T is strongly enhancedat low temperatures, reaching as high as 8 , J/mole , Ce · K
2 at 0.2 , K.This leads to the conclusion that Ce
3Pd
20Si
6 is one ofthe heaviest-electron systems.
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Shigenori Nagatomo, Sadamu Takeda, Kizashi Yamaguchi, Makoto Iwata, Yo ...
Subject area: Magnetics resonances and relaxations in condensed matter; MÖssbauer effect.
1995 Volume 64 Issue 2 Pages
391-394
Published: February 01, 1995
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A new phase transition of (CH
3NH
3)
5Bi
2Cl
11 was found at 520, K by proton NMR and differential thermal analysis. By the phase transition, the activation energy of translational diffusion of CH
3NH
3+ cation was reduced from 83, kJ/mol to 29, kJ/mol. Rotational motion of the cation in the low-temperature phase is also discussed.
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Mamoru Tanibayashi
Subject area: Mathematical methods in physics.
1995 Volume 64 Issue 2 Pages
395-400
Published: February 01, 1995
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An analytical formula is given for the power spectrum of a one dimensional system which is made up of two components in the Fibonacci sequence. In order to demonstrate the usefulness of the formula in the analysis of experimental results, we carried out an experiment, in which resonant oscillation is excited in a weakly damped harmonic oscillator by two species of pulses in the Fibonacci sequence.
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R. S. Banerjee
Subject area: Mathematical methods in physics.
1995 Volume 64 Issue 2 Pages
401-402
Published: February 01, 1995
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The Painlevé analysis of a new coupled dispersionless equations (recently suggestedby Konno and Oono) is performed. It is shown that the equations do possess Painlevé property.
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Kazuaki Nakayama, Jens Hoppe, Miki Wadati
Subject area: Mathematical methods in physics.
1995 Volume 64 Issue 2 Pages
403-407
Published: February 01, 1995
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Level-set approach to the motion of surfaces is presented. Applications to geometrical models in condensed matter physics are given. The finger solution and its generalizations, which were reported very recently, are derived in a simple way.
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Masato Hisakado, Miki Wadati
Subject area: Mathematical methods in physics.
1995 Volume 64 Issue 2 Pages
408-413
Published: February 01, 1995
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Presented is a set of integrable multi-component hybrid nonlinear Schrödinger (MCHNS) equations. Each multi-component equation is a superposition of the nonlinear Schrödinger (NS) equation and the derivative nonlinear Schrödinger (DNS)equation. For the MCHNS equations, the inverse scattering formulation is given. The gauge transformation relating 2-component hybrid nonlinear Schrödinger equation with the Manakov equation is explicitly shown. This also confirms that the former is integrable since the latter is integrable.
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Yoshihiro Nishiyama, Keisuke Totsuka, Naomichi Hatano, Masuo Suzuki
Subject area: Statistical physics and thermodynamics.
1995 Volume 64 Issue 2 Pages
414-422
Published: February 01, 1995
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The S=2 antiferromagnetic Heisenberg open chain is analyzed with the real-space numerical renormalization-group method improved by White. The low-lying spectrum and the one-point function are evaluated to show the degeneracy and the boundary effect on the ground state. Generalized string correlation functions were calculated for θ =π and θ =π\frasl2. The θ =π\frasl2 string correlation is found to indicate the long-range hidden order of the ground state. These results are quite consistent with the S=2 VBS argument.
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Hiroshi Takano, Seiji Miyashita
Subject area: Statistical physics and thermodynamics.
1995 Volume 64 Issue 2 Pages
423-429
Published: February 01, 1995
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Relaxation phenomena are studied for the ± J Ising spin glass in two dimensions by Monte Carlo method. For each spin, a representative relaxation time of the spin is estimated from the equilibrium autocorrelation function of the spin. Clusters of slowly relaxing spins are found to exist below the critical temperature of the nonrandom Ising ferromagnet. It is also found that the distribution of the relaxation times of spins is consistent with the prediction of the theory which assumes independent motion of clusters. This distribution explains the nonexponential decay of the averaged spin autocorrelation function as in the case of the diluted Ising ferromagnets.
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Toshiya Ohtsuki, Daisuke Kinoshita, Yoshikazu Takemoto, Akihisa Hayash ...
Subject area: Statistical physics and thermodynamics.
1995 Volume 64 Issue 2 Pages
430-434
Published: February 01, 1995
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Segregation by shaking in cohesionless granular mixtures is investigated by Molecular Dynamics simulations, where granular particles are modeled by inelastic hard discs. Temporal evolution of the height h of one tagged particle immersed in a set of monodisperse particles is pursued for various values of the particle size and density. The existence of the steady state independent of initial conditions is elucidated. The height h
∞ at the steady state is a continuously varying function of the particle size and density. With increasing size, h
∞ reaches a maximum after rapid increase, whereas h
∞ decreases with increasing density.
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Fumiaki Yabuki, Koya Abe, Katsuya Amako, Yasuo Arai, Tatsumi Arima, Yu ...
Subject area: Specific reactions and phenomenology.
1995 Volume 64 Issue 2 Pages
435-447
Published: February 01, 1995
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We measured the cross section for the γ γ → π
+π
- process in the pion pair invariant mass range of 1.0--1.5, GeV/c
2 with the VENUS detector at TRISTAN. The γ γ decay width of the f
2(1270) resonance was obtained by using Vermaseren's model and a partial wave analysis. The results from both analyses were in good agreement. The partial wave analysis indicated the presence of a J=0 component around at 1.2, GeV/c
2 with a resonance-like structure.
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Michio Sasanuma
Subject area: Heat flow, thermal and thermodynamic processes.
1995 Volume 64 Issue 2 Pages
448-455
Published: February 01, 1995
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Experimental examination of the reflection of light at the surface of noble metals at high temperature shows non existence of the radiative equilibrium condition and the induced emission. Interpretation of the thermal radiation is given without using the Planck's radiation formula and the Kirchhoff's law. Temperature shifts of the spectral peak of the emission band with increasing temperature are calculated by a quantum mechanical model, where the radiation is induced by an electron transition between two potentials and the spectral shape and shifts are determined by the Boltzmann factor in the potentials.
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Takahumi Miyazaki, Akio Harada, Nobuaki Ikuta
Subject area: Kinetic and transport theory of fluids; physical properties of gases.
1995 Volume 64 Issue 2 Pages
456-462
Published: February 01, 1995
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The velocity distribution and transport properties of model gases in thermal equilibrium at 300, K with mass of He having three cross sections proportional to the power of relative speed as v
r0, v
r-1/2 and v
r-1 are calculated by using the flight time integral (FTI) method. Gas particles of all the cross sections are settled in a Maxwell distribution with a mean energy of 3kT
g/2e, eV, but some of transport properties, mean colliding energies, reaction rates take different values due to relative velocity dependent cross sections even reduced to a common mean collision frequency. The fact that the gas can have different transport properties and reaction rates in the same temperature and collision frequency is noticeable.
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Ryutaro Kanno, Akio Ishida, Loren C. Steinhauer
Subject area: The physics of plasmas and electric discharges.
1995 Volume 64 Issue 2 Pages
463-478
Published: February 01, 1995
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The tilting mode in field-reversed configurations (FRC) is examined using ideal-magnetohydrodynamic stability theory. Tilting, a global mode, is the greatest threat for disruption of FRC confinement. Previous studies uniformly found tilting to be unstable in ideal theory: the objective here is to ascertain if stable equilibria were overlooked in past work. Solving the variational problem with the Rayleigh-Ritz technique, tilting-stable equilibria are found for sufficiently hollow current profile and sufficient racetrackness of the separatrix shape. Although these equilibria were not examined previously, the present conclusion is quite surprising. Consequently checks of the method are offered. Even so it cannot yet be claimed with complete certainty that stability has been proved: absolute confirmation of ideal-stable tilting awaits the application of more complete methods.
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Kazuyuki Itoh, Hiroshi Ohno, Shunji Kuragaki
Subject area: Structure of liquids and solids; crystallography.
1995 Volume 64 Issue 2 Pages
479-484
Published: February 01, 1995
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We determined the paraelectric crystal structure of RbHSO
4 using X-ray diffraction intensities collected by an automatic four-circle diffractometer. One of the two independent SO
4 ions takes two molecular arrangements with equal probability while the other SO
4 ion occupies a single site. The ferroelectric structure is estimated from the disordered paraelectric structure to deduce a plausible spontaneous polarization. We conclude that the ferroelectric phase transition is driven by the disordering of the SO
4 ions. The H atom connecting these ions is located near one of the two SO
4 ions and executes large thermal motion. This result is interpreted by the riding model of the H atom associated with the disordering of the SO
4 ion.
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Takuya Tsuzuki, Makoto Yao, Hirohisa Endo
Subject area: Structure of liquids and solids; crystallography.
1995 Volume 64 Issue 2 Pages
485-503
Published: February 01, 1995
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The measurements of EXAFS for liquid Te and liquid Te--Se mixtures, and neutron diffraction for liquid Te were carried out to study the static structure of liquid Te in a wide temperature range from near the melting point to a low temperature in the supercooled liquid state. The dynamic structure of liquid Te was also studied by means of quasielastic and inelastic neutron scatterings. It is found that near the melting point, liquid Te has a twofold coordinated chain structure consisting of long and short covalent bonds, and a strong interchain correlation exists between those chains. As the temperature decreases from the melting point, the number of the long bonds is reduced and the local structure changes substantially accompanied by the reduction of the interchain correlation. It is considered that the long bonds and the strong interchain correlation are associated with the metallic nature of liquid Te.
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Takaaki Ukeda, Kazuyuki Itoh, Chikako Moriyoshi
Subject area: Structure of liquids and solids; crystallography.
1995 Volume 64 Issue 2 Pages
504-512
Published: February 01, 1995
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Accurate crystal structure of K
2Mn
2(SO
4)
3 was determined at several temperatures in the high-temperature phase. It turns out from the split-atom calculation that the SO
4 ion takes two reorientational arrangements as has been implied in the early studies. Thermal vibrations of all the constituent atoms become large with approaching the phase transition temperature. We conclude that the coexistence of the disordered motions and the soft vibrations arises from the short Mn--O distances which govern the driving mechanism of the phase transition.
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Z. J. Li, Z. An, K. L. Yao
Subject area: Lattice dynamics and crystal statistics.
1995 Volume 64 Issue 2 Pages
513-517
Published: February 01, 1995
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We have studied the energy spectra of polaron and the localized vibrational modes around a polaron in the weakly coupled electron-phonon systems by using an extension of SSH model that includes the second-nearest neighbor hopping interactions. The results show that (1) The electron-hole symmetry of the energy band structure is broken and the energy gap 2Δ is slightly increased. (2) The number of localized electronic states and their location are changed as in the soliton case. (3) For a negative polaron, eight localized modes have been found, compared with seven in the previous results. (4) The energy spectra of polaron and the localized modes are related to the types of polarons by turning on the second-neighbor hopping interactions.
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Wenxiu Gao, Minoru Sasaki, Hiroshi Negishi, Masasi Inoue, Vladimir A. ...
Subject area: Electronic transport in condensed matter.
1995 Volume 64 Issue 2 Pages
518-526
Published: February 01, 1995
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The pulsed-laser induced “ transient thermoelectric effect (TTE) \
q \
q of a quasi-two-dimensional γ-Mo
4O
11 crystal has been measured under a static electric field over the time range 50, ns--100, ms and temperature range 6--300, K. Upon application of static electric field, the TTE voltages are enhanced and most of these signals change their sign for reversal of the field direction, which is attributable to the change in photoinduced \lq ambipolar states'. The TTE voltages are characterized by photo-generated carrier diffusions with four relaxation times τ
i (i=1-4), from which we have evaluated the carrier mobilities μ
i. Using our dynamic data and existing block-band model, we have self-consistently calculated the temperature dependence of the dc transport quantities, in satisfactory agreement with the experiments. The difference in the electronic properties for γ - and its similar η -type Mo
4O
11 is also discussed.
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Hiroyuki Yamaguchi, Tomohiro Yamaguchi, Seiichi Kagoshima, Taizo Masum ...
Subject area: Electronic transport in condensed matter.
1995 Volume 64 Issue 2 Pages
527-532
Published: February 01, 1995
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We studied pulsed photoconductivity of face-centered-cubic C
60 single crystals in the temperature range 4--300, K and the wave-length one 337--780 nm. Dominant photocarriers turned out to be electrons. We found photoconductivity anomalies at 85, K, 155, K and 260, K where structural phase transitions have been found or are expected to occur in the rotational degree of freedom of C
60 clusters. The anomaly at 155, K was found to be quenched by ambient oxygen.
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Yukio Okunuki, Nobuo Môri, Akira Ochiai, Yoshinori Haga, Takashi ...
Subject area: Electronic transport in condensed matter.
1995 Volume 64 Issue 2 Pages
533-539
Published: February 01, 1995
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We have investigated the transport properties and their pressure effects on Yb
4As
3, which shows a heavy Fermion property with extremely low carrier concentration. Temperature dependence of the resistivity and of the Hall coefficient under high pressure up to 1.2, GPa was measured in the temperature range from 4.2, K to 320, K. A remarkable change in both resistivity and the Hall coefficient was revealed under high pressure in the whole temperature range. The inverse Hall mobility was found to show no peak even under high pressure at the temperature where the resistivity and the Hall coefficient have a broad one. These results indicate that the carrier number changes drastically with temperature and pressure. We show that these anomalous behavior can be explained well by a two-band model at least in the low temperature region. This model suggests that a narrow band with high density of states reflecting the large γ -value plays an important role on the transport properties in Yb
4As
3.
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Kohji Sonoda, Kozo Hoshino, Mitsuo Watabe
Subject area: Electronic structure and electrical properties of surfaces, interfaces and thin films.
1995 Volume 64 Issue 2 Pages
540-548
Published: February 01, 1995
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We have investigated the feature of the screening effect in metal clusters to clarify how it differs from that in bulk metals. For this purpose we employ a jellium sphere as a model for a metal cluster and calculate the change in the electronic states when an extra positive point charge is introduced at its center, by solving the Kohn-Sham equation in the local-density approximation. The screening charge density around the extra charge is estimated by subtracting the charge induced near the cluster surface from the total induced charge density thus calculated. It is found for sodium clusters that, even for small clusters with the number of atoms N=20, 40 and 58, the screening effect is similar to that in the bulk jellium and that the screening charge distributions for larger clusters with N=92 and 198 almost coincide with that in the bulk.
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Seiji Higashitani, Katsuhiko Nagai
Subject area: Superconductivity.
1995 Volume 64 Issue 2 Pages
549-564
Published: February 01, 1995
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The Meissner effect in normal-superconducting proximity-contact double layers is discussed in the clean limit. The diamagnetic current is calculated using the quasi-classical Green's function. We obtain the quasi-classical Green's function linear in the vector potential in the proximity-contact double layers with a finite reflection coefficient at the interface. It is found that the diamagnetic current in the clean normal layer is constant in space, therefore, the magnetic field linearly decreases in the clean normal layer. We give an explicit expression for the screening length in the clean normal layer and study its temperature dependence. We show that the temperature dependence in the clean normal layer is considerably different from that in the dirty normal layer and agrees with a recent experiment in Au--Nb system.
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Yasusi Koyama, Yositake Takane, Hiromichi Ebisawa
Subject area: Superconductivity.
1995 Volume 64 Issue 2 Pages
565-571
Published: February 01, 1995
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We modify the Blonder, Tinkham and Klapwijk theory to calculate the differential conductance of the interface between the normal conductor and the d-wave superconductor at zero temperature. The differential conductance is calculated as a function of the bias voltage in the absence or presence of the barrier potential at the interface. It is shown that the behavior of the conductance in the case of the d-wave symmetry is quite different from that in the case of the s-wave symmetry. Thus the information of the symmetry for the Cooper pair should be obtained from the quasiparticle transport phenomena at the normal-superconducting microconstriction.
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Tetsutaro Inoue, Taro Kuroda, Kiyohiro Sugiyama, Yoshinori Haga, Takas ...
Subject area: Magnetic properties and materials.
1995 Volume 64 Issue 2 Pages
572-580
Published: February 01, 1995
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The high-field magnetization of low carrier semimetallic CeP is investigated in the temperature region from 1.3, K to 77, K and applied fields in the {100} and {110} planes up to 64, Tesla (T). A ferrimagnetic state in the low field region changes to an antiferromagnetic state by the application of the field below 10, T. Above 20, T, multi-step magnetizations of the Ce moment related with the Landau level crossing of the conduction electron are observed. The critical fields are almost temperature independent below 35, K. This phenomenon is explained by the Stoner-Landau model that the spin population change in the low concentration conduction electron system at the crossing field induces magnetic phase changes in the Ce spin system. Each critical field is angular dependent.
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Nobuyoshi Hosoito, Teruo Ono, Hidefumi Yamamoto, Teruya Shinjo, Yasuo ...
Subject area: Magnetic properties and materials.
1995 Volume 64 Issue 2 Pages
581-587
Published: February 01, 1995
Released on J-STAGE: October 01, 1999
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By polarized neutron diffraction, a long range antiparallel alignment of Co and NiFe(permalloy) layer magnetizations is confirmed in a non-coupled Co(10, Å)/Cu(36, Å)/NiFe(10, Å)/Cu(36, Å) giant magnetoresistance system. A general relationship between the magnetoresistance and the magnetization vectors of the Co and NiFe layers under various magnetic fields and temperatures is experimentally derived. The observed large temperature change in the magnetoresistance ratio is understood with this relationship.
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Ikuo Nakai
Subject area: Magnetic properties and materials.
1995 Volume 64 Issue 2 Pages
588-594
Published: February 01, 1995
Released on J-STAGE: October 01, 1999
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We have investigated the longitudinal fluctuation of the local magnetization for an amorphous ferrimagnet Gd
65Co
35 using the precise measurement of the magnetization curve below 5.3, T. The longitudinal fluctuation varies as ST
2 with temperature T. The parameter S depends on the magnetic field B as S=S
0(1-S
1B). A linear combination of the longitudinal and transverse fluctuations well accounts for the field and temperature dependence of the magnetization below 120, K except near 4.2, K. The ferrimagnet shows a weak random magnetic anisotropy at low temperatures, which causes the magnetic isotherm at 4.2, K to approach to saturation as B
-1/2.
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Masahito Yamaga, Kiyoshi Kawamura
Subject area: Magnetic properties and materials.
1995 Volume 64 Issue 2 Pages
595-604
Published: February 01, 1995
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The Kondo effect in the system where localized spins are mutually coupled in investigated, taking account of the dynamics of internal magnetic fields applied to a scattering center. Results show that it is not the magnitude of internal magnetic fields but its fluctuation multiplied by a correlation time to determine whether the Kondo effect appears or not.
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Tosizumi Aoki
Subject area: Magnetic properties and materials.
1995 Volume 64 Issue 2 Pages
605-611
Published: February 01, 1995
Released on J-STAGE: October 01, 1999
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The ground-state properties of the S=1/2 spatially anisotropic Heisenberg antiferromagnet on the square lattice are investigated by use of the self-consistent spin-wave approach, in which the effect of kinematical interaction between spin waves is taken into account seriously. In terms of an anisotropic parameter λ, our result can be expressed as follows: At finite λ, Néel-ordered ground state is always stabilized and only in the limit of vanishing λ, a disordered ground state can be realized, where λ =1 corresponds to spatially isotropic case and λ =0 to extremely anisotropic case in which the system becomes spin chains. The present result is in contradiction to the recent work of Parola, Sorella and Zhong, but in agreement with the one of Sakai and Takahashi based on the interchain mean-field theory.
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Takehiko Oguchi, Hidetsugu Kitatani
Subject area: Magnetic properties and materials.
1995 Volume 64 Issue 2 Pages
612-616
Published: February 01, 1995
Released on J-STAGE: October 01, 1999
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The dimer state for the spin-1/2 quantum Heisenberg antiferromagnet is studied using the theory of resonating valence bond. The present theory is systematic and much more simple than the other theories. We obtain two important theorems. By use of them we can get the dimer eigen state in the linear chain, ladder, square and simple cubic lattices by the unified way. If the relations between exchange integrals are satisfied, the obtained dimer eigen state is the ground state.
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Hideki Yoshizawa, Yasushi Okayama, Yasuaki Oohara, Hiroki Takahashi, N ...
Subject area: Magnetic properties and materials.
1995 Volume 64 Issue 2 Pages
617-630
Published: February 01, 1995
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Pressure effects on crystal electric field (CEF) excitations in ultra-low carrier systems CeP and CeAs have been studied up to 2.8, GPa. There are two critical pressures P
c and P
B: 0.25, GPa and 1.1, GPa for CeP, while 1.3, GPa and 2.5, GPa for CeAs, respectively. CEF excitations are well-defined for P
B, and there is no anomaly at the onset pressure of the ferromagnetic order, Pc. In contrast, striking anomalies have been observed around PB. For CeP, the CEF excitation decreases to 12, meV and a new CEF excitation appears at 9, meV near PB, then it gradually replaces the first one above PB. For CeAs, a CEF excitation exhibits strong softening as well as broadening near PB. Finally, the CEF spectra exhibit strong broadening around 40, K in the low tempe rature phase near and above PB.
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Teodor N. Khazanovich, Nikolai R. Skrynnikov
Subject area: Magnetics resonances and relaxations in condensed matter; MÖssbauer effect.
1995 Volume 64 Issue 2 Pages
631-635
Published: February 01, 1995
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The errors that may arise from the use of the external random field (ERF) approximation in the spin relaxation theory are estimated for the case of a binary solution. The experiments by M. Ishiwata and Y. Ishii (J. Phys. Soc. Jpn. 60 (1991) 1379, ibid. 60 (1991) 1743) have been analyzed. Coupled spin-lattice relaxation of solute molecules has been measured in the experiments where the solvent spin system was exposed to the effect of nonselective pulses. Going beyond the ERF model we assume that the behavior of a solvent spin system can be characterized by a single polarization. This approach involves the consideration ofcoupled solvent-solute relaxation (CSSR). It has been found that the parametersof molecular motion, extracted with the CSSR approach, differ noticeably from those obtained within the scope of the ERF model. We conclude that if the solvent spin system is perturbed during the experiment and its spin-lattice relaxation time is not too short, the CSSR approach should be recommended for quantitative study of the motion of solute molecules.
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Mitsumasa Ishiwata, Takashi Ono
Subject area: Magnetics resonances and relaxations in condensed matter; MÖssbauer effect.
1995 Volume 64 Issue 2 Pages
636-642
Published: February 01, 1995
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13C and
1H relaxations of
13C-enriched chloroform dissolved in the smectic A phase of S2 are measured at 90, MHz for
1H. From various experiments for the coupled spinsystem together with
1H-data for the same mol\with natural abundance of
13C, we have separated spectral densities on reorientation of a molecular axis of the chloroform. They are markedly different from those expected from the purely rotational dynamics; namely, only the component for fluctuation of a dipolar field in the direction of the magnetic field, which has a nonzero average in the ordered state, have been fairly large and frequency-dependent. This result is presumably due to the coupling of translational and rotational motions of the solute deeply inherent in the smectic phase.
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Toshihiro Yamanishi, Tatsuo Kanashiro, Yoshitaka Michihiro, Yutaka Kis ...
Subject area: Magnetics resonances and relaxations in condensed matter; MÖssbauer effect.
1995 Volume 64 Issue 2 Pages
643-650
Published: February 01, 1995
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The results of the temperature dependence of nuclear relaxation rate, 1/T
1 measured for
23Na,
35Cl and
79Br in AgX and NaX with X being Cl and Br are interpreted in terms of the quadrupole relaxation due to lattice vibrations and defect motions. The data of 1/T
1 in the low temperature region are compared with a model calculation based on an ionic model, in which the degree of covalency is estimated. The result is 24.5\an order of magnitude larger than the values in sodium halides. On the other hand, from an analysis of 1/T
1 data in the high temperature region, the migration and formation energies of defects are evaluated and compared with the results of previous conductivity measurements. The obtained activation energies for migration are 0.27, eV in AgBr, 0.23, eV in AgCl and 0.60, eV in NaCl.
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Naoki Matsuura, Kikuo Cho
Subject area: Optical properties and condensedmatter spectroscopy and other interactions of matter with particles and radiation.
1995 Volume 64 Issue 2 Pages
651-662
Published: February 01, 1995
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As an application of the nonlocal theory of radiation matter interaction, pump-probe spectra for ultrathin (<500, Å) platelets of CuCl have been calculated for the pumping condition between exciton and biexciton levels. Typical aspects such as (1) pump induced absorption to biexciton states, and (2) optical Stark shift and resonant broadening of size quantized exciton levels can be seen in the calculated response spectra. The spatial variation of the light field inside the samples depends sensitively on the frequency and slab thickness, which is clearly reflected in the response spectra as quasi k-selection rule. For thicker samples the k-selection rule becomes more strictly valid, as expected.
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Yo Horikawa
Subject area: Biophysics.
1995 Volume 64 Issue 2 Pages
663-666
Published: February 01, 1995
Released on J-STAGE: October 01, 1999
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Effects of velocity dispersion and noise on spike propagation in excitable media are studied. Mutual information of the interspike intervals of a spike train before and after propagation is derived through a kinematic equation. There is the mean interspike interval that has the maximum mutual information.
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JunIchiro Tada, Kazuaki Katoh
Subject area: Other areas of research of general interest to physicists.
1995 Volume 64 Issue 2 Pages
667-673
Published: February 01, 1995
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The concept of the “ absorbed dose'' of ionizing radiation is scrutinized from physical point of view. It is shown that the concept and definition of the quantity in the ICRU system is disqualified as a physical quantity and the absorbed dose can not always be a “ measure of cause'' in describing causality relation between radiation and effects on matter. The current absorbed dose depends even on the energy that have already been brought out from the matter, contrary to the intention of introducing the quantity. Trials to remove these difficulties are made. However, it is also shown there still exists an essential problem that cannot be solved by improving the formulation.
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Kazuo Suzuki
Subject area: Structure of liquids and solids; crystallography.
1995 Volume 64 Issue 2 Pages
674-675
Published: February 01, 1995
Released on J-STAGE: October 01, 1999
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