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Takahiro Nitta, Hideaki Kato, Hisashi Haga, Koji Nemoto, Kazushige Kaw ...
2005 Volume 74 Issue 11 Pages
2875-2879
Published: November 15, 2005
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We measure the static friction
Fc of agar gels on glass substrates immersed in water.
Fc is independent of the nominal contact area, and increases with the normal load and the duration
tw of contact prior to sliding. Using a confocal laser-scanning microscope, many fine dark spots are clearly visible in the optical reflection distribution images on the glass interface in contact with the gel. The total area of the dark spots increases with
tw, corresponding qualitatively to that of
Fc. These observations indicate that
Fc originates from the formation of the contacting spots at the interface, which is not due to asperities of the gel surface alone but related to the drainage of water trapped by the gel polymer network at the frictional interface.
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Shigemasa Suga, Akira Sekiyama, Shin Imada, Akihiko Shigemoto, Atsushi ...
2005 Volume 74 Issue 11 Pages
2880-2884
Published: November 15, 2005
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By use of high-resolution soft X-rays, intrinsic temperature dependences of bulk Yb 4f photoelectron spectra were obtained for fractured surfaces of high-purity YbAl
3 single crystals. The spectra of not only bulk 4f
13 but also 4f
12 final states are analyzed by noncrossing approximation (NCA) calculation for the f
14, f
13, and f
12 initial states based on the single impurity Anderson model (SIAM). In order to consistently interpret the temperature dependences of both 4f
13 and 4f
12 final states, however, it is found that a constant set of parameters of the hybridization strength Δ, bare 4f energy ε
f and electron correlation energy
Uff is insufficient. The limitation of SIAM is confirmed for YbAl
3 and the importance of the Kondo lattice effects is suggested.
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Kazuhiro Sano, Yoshiaki Ono, Yuh Yamada
2005 Volume 74 Issue 11 Pages
2885-2888
Published: November 15, 2005
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Recently, Matsukawa
et al. discovered a new superconductor, Pr
2Ba
4Cu
7O
15−δ, in which metallic CuO double chains are responsible for the superconductivity. To investigate its superconductivity, we employ the
d–
p double chain model where the tight-binding parameters are determined so as to fit a band structure in the local density approximation (LDA). On the basis of the Tomonaga–Luttinger liquid theory, we obtain a phase diagram that includes the superconducting phase in the weak coupling limit. We also calculate the Luttinger liquid parameter
Kρ as a function of the electron density
n using the Hartree–Fock approximation. With increasing
n from quarter filling,
Kρ increases and then exceeds 1/2 when the superconducting correlation becomes most dominant.
Kρ has a maximum at an optimal density between quarter- and half-filling. These results are consistent with the experimental observation.
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Yoshinori Haga, Dai Aoki, Hiroshi Yamagami, Tatsuma D. Matsuda, Kunihi ...
2005 Volume 74 Issue 11 Pages
2889-2892
Published: November 15, 2005
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We observed de Haas–van Alphen (dHvA) oscillation in a paramagnetic plutonium compound, PuIn
3. In the present paper, we report the first observation of dHvA effect in plutonium compounds. One detected dHvA branch named γ corresponds to a closed band-27 electron Fermi surface, where three kinds of closed Fermi surfaces are calculated on the basis of the 5
f-itinerant band model. The cyclotron mass of branch γ was determined as 4.8
m0. The dHvA signals are found to be extremely reduced as a function of time due to point defects produced by α-decay of
239Pu.
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Yoichi Tanabe, Tadashi Adachi, Takashi Noji, Yoji Koike
2005 Volume 74 Issue 11 Pages
2893-2896
Published: November 15, 2005
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We have grown a single crystal of La
2−xSr
xCuO
4 in which the Sr concentration,
x, continuously changes from 0.24 to 0.29 in the overdoped regime and obtained many pieces of single crystals with different
x values by slicing the single crystal. From detailed measurements of the magnetic susceptibility, χ, of each piece, it has been found that the absolute value of χ at the measured lowest temperature 2 K, |χ
2 K|, on field cooling rapidly decreases with increasing
x as well as the superconducting (SC) transition temperature. As the value of |χ
2 K| is regarded as corresponding to the SC volume fraction in a sample, it has been concluded that a phase separation into SC and normal-state regions occurs in a sample of La
2−xSr
xCuO
4 in the overdoped regime.
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Akito Kobayashi, Shinya Katayama, Yoshikazu Suzumura
2005 Volume 74 Issue 11 Pages
2897-2900
Published: November 15, 2005
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The superconductivity that occurs below the charge ordering temperature in a quasi-two-dimensional (quasi-2D) organic conductor, the α-(ET)
2I
3 salt, has been examined by applying the mean field theory and the random phase approximation to the extended Hubbard model with four sites in the unit cell and anisotropic nearest-neighbor interactions. It is shown that, under uniaxial pressure, the insulating phase moves to the metal phase with small pockets of electrons and holes, while the charge ordering state with the horizontal stripe pattern is retained. The novel property of the metal phase gives rise to the superconducting (SC) state with the full gap. It is found that the pairing interaction for the superconductivity is given mainly by the spin fluctuation existing between hole-rich sites in the unit cell. The role of the anisotropic repulsive interaction is discussed for the mechanism of the present SC state.
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Hiroshi Watanabe, Masao Ogata
2005 Volume 74 Issue 11 Pages
2901-2904
Published: November 15, 2005
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To investigate the possibility of charge order and superconductivity in a doped two-dimensional triangular lattice, we study an extended Hubbard model with the variational Monte Carlo method. At
n=2⁄3, a commensurate filling for a triangular lattice, it is shown that the nearest-neighbor Coulomb interaction
V induces honeycomb-type charge order and antiferromagnetic spin order at
U\\gtrsim10
t. We also discuss the possibility of superconductivity induced by charge fluctuation and the relation to the superconductivity in Na
0.35CoO
2·1.3H
2O and θ-type organic condoctors.
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Masafumi Udagawa, Youichi Yanase, Masao Ogata
2005 Volume 74 Issue 11 Pages
2905-2908
Published: November 15, 2005
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We have studied the superconducting state of Sr
2RuO
4 under a magnetic field parallel to the superconducting plane. We show that due to a weak spin–orbit coupling, a nonunitary
ky(\\hat
z−
iα\\hat
y) state is formed right at
Hc2, which then changes to a unitary
ky\\hat
z state as the magnetic field is lowered. On the basis of this crossover, we address the origin of the observed double peaks of specific heat and the disappearance of the double peaks at low fields.
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Hiroya Sakurai, Kazunori Takada, Takayoshi Sasaki, Eiji Takayama-Murom ...
2005 Volume 74 Issue 11 Pages
2909-2912
Published: November 15, 2005
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We discovered that oxonium (H
3O
+) ion content is a key parameter to the understanding of unique superconductivity in sodium cobalt oxyhydrate. As Na
+ ions are substituted by H
3O
+ ions, keeping the Co valence constant, the superconducting phase is transformed into a magnetically ordered phase, and then into a hitherto hidden superconducting phase. Furthermore, the superconducting phase previously discovered is suppressed by the magnetic phase under application of a magnetic field. These facts indicate that the superconductivity is induced by magnetic interactions which are substantially governed by the oxonium ion content.
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Shuji Kishimoto, Akihiro Kondo, Moo-Sung Kim, Hideki Tou, Masafumi Ser ...
2005 Volume 74 Issue 11 Pages
2913-2916
Published: November 15, 2005
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We have investigated the physical properties of Ce
0.7Pr
0.3B
6 in order to clarify the doping effect on the multipolar interactions in CeB
6 and PrB
6. As a result of the suppression of the antiferro-quadrupolar ordering temperature
TQ and the enhancement of
TN by Pr doping, six long-range ordered (LRO) phases appear.
TQ exhibits a smooth increase with increasing magnetic field as in CeB
6. At a high magnetic field, above ∼10 T, only phase II exists. As for the three LRO phases below ∼10 T and below
TQ, there exists a possibility of incommensurate quadrupolar and magnetic ordering. A new question of how the quadrupolar ordering is compatible with the magnetic ordering appears in the present study. The coexistence of the magnetic and quadrupolar orderings in Ce
0.7Pr
0.3B
6 indicates that the strong Ce–Pr interaction is different from the weak Ce–Nd interaction in Ce
xNd
1−xB
6.
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Yasuo Yoshida, Osamu Wada, Yuji Inagaki, Takayuki Asano, Kenji Takeo, ...
2005 Volume 74 Issue 11 Pages
2917-2920
Published: November 15, 2005
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Specific heat measurements in a magnetic field up to 8 T have been performed on an
S=1⁄2 weakly coupled alternating ferromagnetic (F) and antiferromagnetic (AF) dimer chain system, (CH
3)
2NH
2CuCl
3. We have observed a spontaneous AF ordering and a field-induced one below and above the 1/2 magnetization plateau field range from 2 to 3.5 T, respectively. The
H–
T phase boundaries for the orderings are completely different from the general reentrant ones of the other quantum spin systems investigated thus far. In the plateau field range, a double-peaked structure is observed in the temperature dependence of specific heat, reflecting the coexistence of F and AF excitations.
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Kazuki Koshino, Hajime Ishihara
2005 Volume 74 Issue 11 Pages
2921-2924
Published: November 15, 2005
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We have investigated the optical response of a superradiant system composed of
N two-level systems, which undergoes three different damping mechanisms: radiative dissipation (γ
r), dephasing (γ
d), and nonradiative dissipation (γ
n). Whereas the roles of γ
d and γ
n are equivalent in the linear susceptibility χ
(1), the third-order nonlinear susceptibility χ
(3) drastically depends on the ratio of γ
d and γ
n: When γ
d\\lesssimγ
n, χ
(3) is essentially that of a single two-level system. In contrast, in the opposite case of γ
d>>
Nγ
n, χ
(3) suffers the size enhancement effect and becomes proportional to the system size
N after an incubation period.
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Hiroyuki Matsuzaki, Hisashi Takamatsu, Hideo Kishida, Hiroshi Okamoto
2005 Volume 74 Issue 11 Pages
2925-2928
Published: November 15, 2005
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A pressure-induced neutral-to-ionic (
N–
I) transition in tetrathiafulvalene-
p-chroranil was studied by infrared vibration spectra. With increasing pressure, two CO stretching bands probing coexisting
N and
I states merge due to rapid valence fluctuations. From the spectral analyses with the exchange-narrowing model, we derive the pressure dependence of the
N–
I exchange rate related to the
N–
I domain-wall motions, which explains the anomalous increase in conductivity under pressure. We also demonstrate a para- to ferro-electric transition at 1.5 GPa as well as the
N–
I transition at 0.95 GPa.
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Hiroshi Ajiki
2005 Volume 74 Issue 11 Pages
2929-2932
Published: November 15, 2005
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We determine the optimal conditions for achieving strong nonlinearity in semiconductor cavities as a function of the
Q factor, coupling constant
g, and longitudinal (γ
1) and pure transverse (γ
2) damping constants. The intensity of the third-order nonlinear field becomes maximum in the strong-coupling regime near the condition γ
1+2γ
2=ω
c⁄2
Q, where ω
c is the cavity-quasimode frequency. However, the most effective optical Kerr effect can be realized in the intermediate-coupling regime. Both of the nonlinearities are enhanced significantly also in the weak-coupling regime satisfying ω
c⁄
Q=(
g2⁄γ
1)[\\sqrt1+8γ
1⁄(γ
1+2γ
2)−1], and their intensities depend only on the damping constants.
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Yasuaki Masumoto, Fumitaka Suto, Michio Ikezawa, Chikako Uchiyama, Mas ...
2005 Volume 74 Issue 11 Pages
2933-2936
Published: November 15, 2005
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A highly sensitive heterodyne-detected photon echo enabled us to observe the signal from one layer of neutral self-assembled InP quantum dots under an electric field. The photon echo signal dramatically increased when charged InP quantum dots were neutralized with the application of negative electric bias. This fact suggests the hypothesis that charged quantum dots do not produce the photon echo. With the further increase of negative electric bias, photoluminescence was quenched and the photon echo decayed faster. The photon echo showed tunneling-induced dephasing and decayed nonexponentially, reflecting the non-Markovian nature of the tunneling process.
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Rui-Feng Zhang, Jia-Hao Li, Bai-Xin Liu
2005 Volume 74 Issue 11 Pages
2937-2940
Published: November 15, 2005
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A dual-phase Y–W metallic glass is observed in nanoscaled Y–W multilayered films upon 200 keV xenon ion irradiation. Diffraction analysis and bright field images reveal that the metallic glass consists of separated glass phases evolved from the Y and W lattices, respectively, through spinodal decomposition, and that the glass features a two-dimensional fractal morphology consisting of the W-based glass phase branches sitting on the Y-based glass substrate. The fractal dimension is determined to be 1.75±0.05, suggesting that the fractal is grown through a cluster-diffusion-limited-aggregation model. Moreover, based on a newly derived n-body Y–W potential, atomistic simulations confirm the possibility of metallic glass formation in the equilibrium immiscible Y–W system.
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Changzheng Qu, Dongbo Zhang
2005 Volume 74 Issue 11 Pages
2941-2944
Published: November 15, 2005
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It is shown that the WKI model of type II which is solved in terms of the WKI scheme arises from the motion of curves in
E3. Its symmetry groups and an one-dimensional optimal system are presented, and the corresponding group-invariant solutions are obtained.
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Jin-Yuan Hsieh, Che-Ming Li, Der-San Chuu
2005 Volume 74 Issue 11 Pages
2945-2948
Published: November 15, 2005
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In this work, an analog analogue of Grover’s quantum search algorithm was studied. A generalized Hamiltonian driving the evolution of a quantum state in the analog search system was derived. Equations relating all parameters considered in the present problem were given according to the required maximal probability for finding the marked state. Using these equations, both the measuring time and the system energy gap suitable for a quantum search with or without certainty can thus be evaluated. Moreover, the reduction of the searching probability caused by a random and uncontrollable phase error for an initial state has been investigated. It was shown that in an efficient quantum search computation, the measuring time should be proportional to the square root of the size of the database.
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Ying Guo, Guihua Zeng
2005 Volume 74 Issue 11 Pages
2949-2956
Published: November 15, 2005
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To simultaneously detect random and burst quantum errors which may be generalized as quantum event errors, a quantum error detection code, called the quantum event-error detection code, is first investigated in analogy to the classical event-error detection code. The proposed code can be used to detect the length, number and location of errors occurring in every error event. Two special quantum event-error detection codes are constructed by exploiting different approaches according to the derived syndrome, and their number-bound of generators of the stabilizer is also derived. Finally, the proposed theory on the quantum event-error detection code for quantum single-event error is extended to a more general case, i.e., the quantum composite-event error, so that the general quantum event-error detection code can be constructed.
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Norikazu Todoroki, Seiji Miyashita
2005 Volume 74 Issue 11 Pages
2957-2960
Published: November 15, 2005
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We consider the Blume–Capel model with quantum tunneling between the excited states. We find a magnetically ordered phase transition induced by quantum fluctuation in the model. The model has no phase transition in the corresponding classical case. Usually, quantum fluctuation breaks the ordered phase, as in the case of the transverse field Ising model. However, in the present case, an ordered phase is enhanced by a quantum fluctuation. Moreover, we find a phase transition between a quantum paramagnetic phase and a classical diamagnetic phase at a zero temperature. We study the properties of the phase transition using mean-field approximation (MFA) and a quantum Monte Carlo method to confirm the result of the MFA.
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Masaki Kawamura, Michiko Yamana, Masato Okada
2005 Volume 74 Issue 11 Pages
2961-2965
Published: November 15, 2005
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We discuss the effects of common synaptic inputs in a recurrent neural network. Because of the effects of these common synaptic inputs, the correlation between neural inputs cannot be ignored, and thus the network exhibits sample dependence. Networks of this type do not have well-defined thermodynamic limits, and self-averaging breaks down. We therefore need to develop a suitable theory without relying on these common properties. While the effects of the common synaptic inputs have been analyzed in layered neural networks, it was apparently difficult to analyze these effects in recurrent neural networks due to feedback connections. We investigated a sequential associative memory model as an example of recurrent networks and succeeded in deriving a macroscopic dynamical description as a recurrence relation form of a probability density function.
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Kazuyuki Hara, Masato Okada
2005 Volume 74 Issue 11 Pages
2966-2972
Published: November 15, 2005
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We analyze ensemble learning including the noisy case where teacher or student noise is present. Linear perceptrons are used as teacher and student. First, we analyze the homogeneous correlation of initial weight vectors. The generalization error consists of two parts: the first term depends on the number of perceptrons
K and is proportional to 1⁄
K, the second does not depend on
K in the first case. In the inhomogeneous correlation of initial weight vectors case, the weighted average could be optimized to minimize the generalization error. We found that the optimal weights do not depend on time without student noise, while the optimal weights depend on time and become 1⁄
K with student noise.
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Kazuo Sasaki
2005 Volume 74 Issue 11 Pages
2973-2980
Published: November 15, 2005
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We propose a simple theoretical model for a molecular chemical engine that catalyzes a chemical reaction and converts the free energy released by the reaction into mechanical work. Binding and unbinding processes of reactant and product molecules to and from the engine are explicitly taken into account. The work delivered by the engine is calculated analytically for infinitely slow (“pseudo-static”) processes, which can be reversible (quasi-static) or irreversible, controlled by an external agent. It is shown that the work larger than the maximum value limited by the second law of thermodynamics can be obtained in a single cycle of operation by chance, although the statistical average of the work never exceeds this limit and the maximum work is delivered if the process is reversible. The mechanism of the energy transduction is also discussed.
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Mariko Segawa, Atsushi Tomyo, Yasuki Nagai, Yasuyuki Temma, Tomohiro M ...
2005 Volume 74 Issue 11 Pages
2981-2986
Published: November 15, 2005
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We have for the first time determined with high precision the energy spectrum of low-energy neutrons (
En<10 keV) which are produced in the
7Li(
p,
n)
7Be reaction, by detecting γ-rays of the
197Au(
n,γ)
198Au reaction whose cross section is known. An anti-Compton NaI(Tl) spectrometer played an essential role in detecting the γ-rays with a good signal to noise ratio by discriminating large background due to thermalized neutrons in the measurement room. The low energy neutrons thus derived were successfully used to measure the
62Ni(
n,γ)
63Ni reaction cross section. The present low energy neutrons could be extensively used for cross section measurements for neutron capture reactions and elastic scatterings from nuclei of nuclear astrophysical interests.
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Shinichiro Toda, Kimitaka Itoh
2005 Volume 74 Issue 11 Pages
2987-2989
Published: November 15, 2005
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A set of model transport equations is analyzed which induces the radial transition of the electric field by use of the theoretical model for the anomalous transport diffusivities as a candidate. Condition for the onset of the transition as well as a scaling relation between the reduced thermal diffusivity and the normalized temperature gradient is obtained. The test of the adopted theoretical model for the anomalous transport diffusivities is done compared with the experimental result in Large Helical Device (LHD).
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Hiroaki Kadowaki, Akihito Nishiyama, Kazuyuki Matsuda, Yutaka Maniwa, ...
2005 Volume 74 Issue 11 Pages
2990-2995
Published: November 15, 2005
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The structure of bundles of single-walled carbon nanotubes (SWNT) has been refined by Rietveld analysis using neutron and X-ray powder diffraction data. Based on previous simulation studies of powder diffraction data of SWNT and standard Rietveld analyses, we have developed a pattern fit technique for SWNT which provides precise structure parameters. We also show that the present technique can be used with the maximum entropy method (MEM), which is complementary to the Rietveld analysis. Using the neutron diffraction data of pristine SWNT, we have successfully reconstructed the density of carbon nuclei and zero density in the inner cavity of SWNT by MEM.
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Akihito Shimofusa, Toru Kuga, Osamu Kido, Hitoshi Suzuki, Yoshio Saito ...
2005 Volume 74 Issue 11 Pages
2996-3001
Published: November 15, 2005
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The change of Ga smoke particles to GaN particles in a plasma field of a mixture of nitrogen and helium gasses has been studied by transmission electron microscopy. The size of Ga drop and amounts of exited nitrogen clearly influenced the single-crystalline nanoparticle growth. Most of the particles had a wurtzite structure. Small crystallites with a zincblende structure were frequently included in a wurtzite particle. When the nitrogen partial pressure became 10 Torr, perfect single-crystal particles less than 30 nm in size were formed.
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C. Stock, H. Luo, D. Viehland, J. F. Li, I. P. Swainson, R. J. Birgene ...
2005 Volume 74 Issue 11 Pages
3002-3010
Published: November 15, 2005
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The temperature and zone dependence of the lattice dynamics in Pb(Mg
1⁄3Nb
2⁄3)O
3 is characterized using neutron inelastic scattering. Through a detailed study of the phonon lineshape and a comparison of the structure factors to SrTiO
3, we conclude that the coupling between the acoustic and optic modes is weak. However, based on a direct comparison between the (110) Brillouin zone where the diffuse scattering is strong to the (220) zone where the diffuse scattering is weak, a strong coupling between the diffuse component and low-energy acoustic phonon mode is observed. We conclude that the coupling to the diffuse component is the reason for several recent conflicting interpretations of the lattice dynamics based on data from zones with a strong diffuse component.
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Tomozo Tomoyose, Nobuaki Shimoji, Kunio Wakamura
2005 Volume 74 Issue 11 Pages
3011-3015
Published: November 15, 2005
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The ground state energy and the wavefunction of proton in the cubic perovskite-type oxides ABO
3 are studied by using the double-well potential constructed from the one-dimensional O–H–O bond. We have found that when the O–O separation between the nearest neighbor oxygens becomes lower than 2.9 A the proton wavefunction spreads over the double-well potential and the proton transfers between the minimum sites in the double-well potential. We have calculated the activation energy
Ea for the proton transfer by using the small polaron model coupled with the lattice vibration of the O–B–O bond-bending mode. The calculated activation energy is found to be
Ea=0.56 eV for the cubic ABO
3. We have also found the B-atom mass dependence that
Ea decreases with the B-atom mass in the O–B–O bond-bending mode. This B-atom mass dependence of
Ea is similar to that shown in the deformed perovskite-type oxides ABO
3.
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Rikio Settai, Tetsuo Kubo, Tomoyuki Shiromoto, Daisuke Honda, Hiroaki ...
2005 Volume 74 Issue 11 Pages
3016-3026
Published: November 15, 2005
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We have studied a change of the Fermi surface in an antiferromagnet CeIn
3 via the de Haas–van Alphen experiment under pressure up to 3 GPa. With increasing pressure
P, the Néel temperature
TN=10 K decreases and becomes zero at a critical pressure
Pc\\simeq2.6 GPa. In the pressure region
P>
Pc, we have observed a large main Fermi surface named
a, which indicates that the electronic state of 4
f electron in CeIn
3 changes from localized to itinerant at
Pc, as observed in the similar antiferromagnets CeRh
2Si
2 and CeRhIn
5. The cyclotron effective mass
mc∗ of this main Fermi surface is extremely enhanced around
Pc:
mc∗\\simeq60
m0 at 2.7 GPa for the magnetic field along the 〈100〉 direction.
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Takeshi Nakanishi, Tsuneya Ando
2005 Volume 74 Issue 11 Pages
3027-3034
Published: November 15, 2005
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The Boltzmann conductivity is calculated for carbon nanotubes in the presence of an Aharonov–Bohm magnetic flux. Effects of impurity scattering are considered at low temperatures and those of electron–phonon scattering are considered at room temperature. Effects of strains and curvature manifest themselves as a prominent conductivity peak as a function of the flux. The appearance of the peak corresponds to the absence of backscattering in metallic linear bands.
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Hiroshi Tsukahara, Tsuneya Ando
2005 Volume 74 Issue 11 Pages
3035-3040
Published: November 15, 2005
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Transport properties of quantum-wire arrays with disorder in the period are studied theoretically within a self-consistent Born approximation. Although no band gap opens to the lowest order because of the flat average potential, a pseudo-band-structure is recovered in higher order due to effects of strong diffuse Bragg scattering as long as the disorder remains small. A pseudo-band-gap manifests itself in the density of states, the spectral function, and the anisotropic conductivities, and modifies the conductivity in the quantum-wire direction qualitatively in the vicinity of the zone boundary.
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Akihiko Sumiyama, Keisuke Nakatsuji, Yosifumi Tsuji, Yasukage Oda, Tak ...
2005 Volume 74 Issue 11 Pages
3041-3045
Published: November 15, 2005
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Josephson critical current
Ic between a single crystal CePt
3Si and Al has been measured for the junctions on the CePt
3Si surface perpendicular to the
a and
c axes. In the magnetic-field dependence of
Ic, a dominant maximum peak at zero field has been observed only for the junction on the
a-axis face thus far, indicating that the Josephson effect is allowed at least for current flow parallel to the
a axis. This result places a restriction on the representations of the order parameter in the noncentrosymmetric superconductor CePt
3Si.
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Mai Yokoi, Taketo Moyoshi, Yoshiaki Kobayashi, Minoru Soda, Yukio Yasu ...
2005 Volume 74 Issue 11 Pages
3046-3056
Published: November 15, 2005
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Data taken by various methods including NMR/NQR and neutron scattering are presented for Na
xCoO
2, particularly Na
0.5CoO
2. Attention has also been paid to the
x dependence of the electronic nature of this system. The pseudo-gap-like behavior observed in the region of
x<
xc∼0.6 is emphasized. For samples with
x≤0.6, signals from two kinds of Co sites with different quadrupole frequencies ν
Q of ∼4.1 and ∼2.8 MHz were observed, and the former ν
Q, which is nearly equal to that of the superconducting system Na
0.3CoO
2·
yH
2O, becomes dominant with decreasing
x to 0.3. For Na
0.5CoO
2, the Co sites with the larger ν
Q have larger magnetic moments. They align antiferromagnetically at
Tc1∼87 K with their direction within the plane, while the Co sites with the smaller ν
Q have smaller moments. They align in the direction parallel to the
c axis. The ordered moments at the two distinct sites exhibit the same
T-dependence, indicating that the existence of these sites is not due to macroscopic phase separation. Although we have observed the splitting of the zero-field NMR signals from Co sites with smaller ν
Q at the second transition temperature
Tc2∼53 K, any other anomaly of the ordered magnetization has not been observed at
Tc2 in the
T-dependences of neutron and NMR data. As
x decreases, the two-dimensional nature of the electrons is enhanced and the antiferromagnetic correlation increases. On the basis of these results, the superconducting pair state in Na
0.3CoO
2·
yH
2O is discussed.
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Tomoya Kishi, Melanie David, Wilson Agerico Diño, Hiroshi Nakan ...
2005 Volume 74 Issue 11 Pages
3057-3059
Published: November 15, 2005
Released on J-STAGE: February 07, 2008
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We investigate magnetic properties of Fe nanoislands on Cu(111) in the relaxed structure within the density functional theory. We observe that the nanoislands exhibit the ferromagnetic properties with large magnetic moment. We find that the change in the magnetic moment of each Fe atom is induced by deposition on Cu(111) and structure relaxation of Fe nanoislands. Moreover, we examine the stability of ferromagnetic states of Fe nanoislands by performing the total energy calculations.
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Nobuyoshi Hosoito, Takuo Ohkochi
2005 Volume 74 Issue 11 Pages
3060-3065
Published: November 15, 2005
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Depth-resolved induced magnetic polarization in the Cu layer of the [Gd (57.4 Å)/Cu (16.5 Å)] multilayer is determined by resonant X-ray magnetic diffraction technique. The X-ray energy was tuned near the Cu
K absorption edge (8981 eV). The resonant magnetic diffraction peaks from second to fourth order were measured at 10 and 75 K by helicity switching combined with field reversal. The analysis indicates that the induced magnetic polarization extends to the center of the Cu layer and that the magnetization polarization distribution scaled to the Gd magnetization is unchanged against temperature. The shape of the magnetic polarization distribution in the Gd/Cu multilayer is different from that predicted theoretically in the Co/Cu multilayer, where the induced magnetic polarization is concentrated mainly at the interface. A possible reason for the different distribution of the magnetic polarization in the Gd/Cu and Co/Cu systems is discussed.
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Kazuhiro Marumoto, Yasuhito Muramatsu, Yoji Nagano, Takamichi Iwata, S ...
2005 Volume 74 Issue 11 Pages
3066-3076
Published: November 15, 2005
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We report electron spin resonance (ESR) studies on field-induced charge carriers in regioregular poly(3-hexylthiophene) (RR-P3HT) and regioregular poly(3-octylthiophene) (RR-P3OT) for metal–insulator–semiconductor (MIS) diode structures with Al
2O
3 as an insulating layer. The field-induced ESR signals (
g∼2.002) were clearly observed; their intensities monotonically increased as the absolute value of the gate bias increased in the accumulation mode with a saturation behavior at higher voltages. The ESR signals were consistent with those of the photogenerated positive polarons in RR-P3HT and RR-P3OT, demonstrating that the carriers are polarons. The transient responses of the field-induced ESR intensity show fast and slow components. The self-organized lamellar molecular orientation was confirmed by the anisotropic ESR signals due to π-electrons, which is semiquantitatively reproduced by an ESR simulation.
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Masahiro Hasuo, Atsuyoshi Shimamoto, Takeshi Fujiwara, Norihiro Okuda, ...
2005 Volume 74 Issue 11 Pages
3077-3081
Published: November 15, 2005
Released on J-STAGE: February 07, 2008
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We have vapor-deposited CuCl films on rutile TiO
2, Al
2O
3 and synthesized quartz surfaces. The photoluminescence spectra of the films with the thickness from 50 to 1500 nm were observed and compared with that of bulk CuCl. The energy position of the free
Z3 exciton luminescence was found to shift to lower energy side with the increase in the film thickness. This phenomenon suggested that the
Z3 exciton polaritons could not relax to the bottleneck region during their lifetime in the thin films. The observed substrate dependence of the spectra suggested that the relaxation was determined by the film thickness rather than the substrates we used in the experiment.
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Michio Ikezawa, Jialong Zhao, Atsushi Kanno, Yasuaki Masumoto
2005 Volume 74 Issue 11 Pages
3082-3087
Published: November 15, 2005
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Confined acoustic phonons in CuBr quantum dots (QDs) are studied for the first time using coherent phonon measurements and persistent spectral hole burning (PSHB) spectroscopy. A size-dependent damped oscillation with sub-THz frequency is observed in femtosecond pump-probe measurements of CuBr QDs in glass. Similarly, a size-dependent acoustic phonon hole with an energy shift of 1–2 meV is observed in PSHB spectra of CuBr QDs in glass and NaBr crystals. The energies of the confined acoustic phonons obtained by the two methods are in good agreement with each other. In addition, there is no difference in size-dependence between the glass matrix and NaBr matrix. The size dependence of acoustic phonons can be explained well as low frequency vibrational modes of CuBr QDs based on an elastic sphere model. The dominant mode is assigned to the
l=2 spheroidal mode, while the
l=0 mode is also observed.
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Kikuo Cho, Jun Ushida, Motoaki Bamba
2005 Volume 74 Issue 11 Pages
3088-3092
Published: November 15, 2005
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We give a general method to calculate photonic band structure in the form of wave number
k as a function of frequency ω, which is required whenever we want to calculate signal intensity related with photonic band structure. This method is based on the fact that the elements of the coefficient matrix for the plane wave expansion of the Maxwell equations contain wave number up to the second order, which allows us to rewrite the original eigenvalue equation for ω
2 into that for wave number. This method is much better, especially for complex wave numbers, than the transfer matrix method of Pendry, which gives the eigenvalues in the form of exp[
ikd]. The present method leads to a good improvement in the calculation of reflectivity spectrum by eliminating unphysical part due to insufficient precision of numerical results, showing the cross-section dependence of a surface of given Miller index more precisely.
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Naomichi Hatano
2005 Volume 74 Issue 11 Pages
3093-3111
Published: November 15, 2005
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The propagation of an electromagnetic wave in a one-dimensional fractal object, the Cantor set, is studied. The transfer matrix of the wave amplitude is formulated and its renormalization transformation is analyzed. The focus is on resonant states in the Cantor set. In Cantor sets of higher generations, some of the resonant states closely approach the real axis of the wave number, leaving between them a wide region free of resonant states. As a result, wide regions of nearly total reflection appear with sharp peaks of the transmission coefficient beside them. It is also revealed that the electromagnetic wave is strongly enhanced and localized in the cavity of the Cantor set near the resonant frequency. The enhancement factor of the wave amplitude at the resonant frequency is approximately 6⁄|η
r|, where η
r is the imaginary part of the corresponding resonant eigenvalue. For example, a resonant state of the lifetime τ
r=4.3 ms and of the enhancement factor
M=7.8×10
7 is found at the resonant frequency ω
r=367 GHz for the Cantor set of the fourth generation of length
L=10 cm made of a medium of the dielectric constant ε=10.
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Takayoshi Ishimoto, Masanori Tachikawa, Hiroaki Tokiwa, Umpei Nagashim ...
2005 Volume 74 Issue 11 Pages
3112-3116
Published: November 15, 2005
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We analyzed isotope effects on the geometrical and electronic relaxations of hydrogen/deuterium-absorbing Pt
nH(D)
− (
n=1–4, 6) clusters using the first principles multi-component molecular orbital (MC_MO) method, which can take into account the quantum effect of the proton/deuteron. The average of Pt–Pt bond distances of the Pt
nH
− clusters was calculated to be no more than 0.004 Å longer than the bond distances of corresponding Pt
nD
− clusters. Calculations on Pt
nH(D)
2 (
n=2–4, 6) clusters clearly demonstrated that significant geometrical differences between Pt–Pt bond distances caused by the isotope effect depend on the number of hydrogen/deuterium atoms. Slight relaxation of the electronic charge densities was observed by the replacement from H to D. The exponent values indicate that the distribution of the wavefunction of proton and deuteron reflected the geometrical changes and electronic charge densities around the proton and deuteron.
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K. Fushimi, H. Kawasuso, M. Toi, E. Aihara, R. Hayami, S. Nakayama, N. ...
2005 Volume 74 Issue 11 Pages
3117-3121
Published: November 15, 2005
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The highly sensitive method to search for WIMPs dark matter particles is proposed. An array of thin NaI(Tl) plate has the great selectivity for distinguishing the WIMPs events and background ones. The principle of signal selection for WIMPs is described. The high sensitivity for SD (spin-dependent) type WIMPs is expected by applying multi-layer system of NaI(Tl) detector.
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Takaya Mitsui, Ryo Masuda, Shinji Kitao, Makoto Seto
2005 Volume 74 Issue 11 Pages
3122-3123
Published: November 15, 2005
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Eiji Hatta
2005 Volume 74 Issue 11 Pages
3124-3125
Published: November 15, 2005
Released on J-STAGE: February 07, 2008
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