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Tsuneya Ando
2005 Volume 74 Issue 3 Pages
777-817
Published: March 15, 2005
Released on J-STAGE: December 06, 2007
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A brief review is given of electronic and transport properties of carbon nanotubes obtained mainly in a
k·
p scheme. The topics include a giant Aharonov–Bohm effect on the band gap and a Landau-level formation in magnetic fields, magnetic properties, interaction effects on the band structure, optical absorption spectra, and exciton effects. Transport properties are also discussed including absence of backward scattering except for scatterers with a potential range smaller than the lattice constant, its extension to multi-channel cases, a conductance quantization in the presence of short-range and strong scatterers such as lattice vacancies, and transport across junctions between nanotubes with different diameters. A continuum model for phonons in the long-wavelength limit and the resistivity determined by phonon scattering are reviewed as well.
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Satoru Morita, Yu Itoh, Kei-ichi Tainaka
2005 Volume 74 Issue 3 Pages
819-822
Published: March 15, 2005
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Interacting population models often exhibit sustained stochastic oscillations, while the corresponding deterministic models present damped oscillations toward stable equilibrium. We study stochastic oscillation using the Langevin equation. We calculate several indicators that correspond to frequency. We find that their values are different.
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Hiroshi Shimahara
2005 Volume 74 Issue 3 Pages
823-826
Published: March 15, 2005
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The possibility of a new first-order phase transition between solid states with different stiffnesses but the same crystal symmetry is shown. The transition is not accompanied by spontaneous symmetry breaking, analogously to the liquid–gas transition. However, it is different from the liquid–gas transition in the aspect that it occurs between ordered phases. An ionic crystal that has two possible states with different ionic charges and close cohesive energies is a candidate in which such a transition is realized. We propose a simple model to describe such a transition, and examine the thermodynamic property in one, two and three dimensions. Expressions of the transition temperatures, the specific heats, and the latent heats are derived for a limiting case. We briefly discuss the possible relevance of the present mechanism of the phase transition to that observed in a biferrocene–fluorotetracyanoquinodimethane (F
1TCNQ) complex.
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Fumiko Ogushi, Satoshi Yukawa, Nobuyasu Ito
2005 Volume 74 Issue 3 Pages
827-830
Published: March 15, 2005
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The heat conduction of the three-dimensional Lennard-Jones particle system is studied using nonequilibrium molecular dynamics simulation. The geometry of the system is a rectangular parallelepiped box of
Lx×
Ly×
Lz dimensions. Two Nosé–Hoover heat baths with different temperatures are attached to the regions near both ends of the
x-direction. The density of the system and temperature of heat bath are selected so that the system is in the supercritical fluid phase. It is observed that the nonequilibrium steady state with a constant temperature gradient
dT⁄
dx and a energy (heat) flux
J is realized after relaxation process from its initial configuration. The ratio of
J to
dT⁄
dx denoted by κ which corresponds to the heat conductivity in the macroscopic limit is estimated for various system sizes
Lx. It is confirmed that κ(
Lx) shows a size dependence as expressed κ
0+
a⁄\\sqrt
Lx and this dependence is consistent with the so-called long-time tail behavior. This κ
0 is regarded as the macroscopic conductivity. This
Lx dependence implies that the heat conductivity κ(
Lx) is low for a nanoscale system. The κ(
Lx) of the
Lx=300 system decreases by about 10% from that of the macroscopic system.The estimated κ
0 turns out to be proportional to the density.
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Yoichiro Yagi, Akio Yoshimori
2005 Volume 74 Issue 3 Pages
831-834
Published: March 15, 2005
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An Indium adsorbed Si(111) (4×1) reconstructed surface seems to undergo a structural phase transition to (8ד2”) at approximately 130 K with decreasing temperature. On the basis of existing experimental and the first principles theoretical results, a simple semi-phenomenological model, using the Ising spin scheme, is presented for this surface system. Its analysis by Monte Carlo simulation shows that the model can account for this peculiar phase transition well.
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Takashi Yanagisawa, Mitake Miyazaki, Kunihiko Yamaji
2005 Volume 74 Issue 3 Pages
835-838
Published: March 15, 2005
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The spectral function of high-temperature superconductors in the underdoped and lightly-doped regions is calculated in order to explain the Fermi arc spectra observed recently by angle-resolved photoemission spectroscopy. We take into account the tilting of CuO octahedra as well as the on-site Coulomb repulsive interaction; the tilted octahedra induce the staggered transfer integral between
px,y orbitals and Cu
t2g orbitals and bring about nontrivial effects of spin–orbit coupling for the
d electrons in the CuO plane. The spectral weight shows a peak at around (π⁄2,π⁄2) for light doping and extends around this point forming an arc as the carrier density increases, where the spectra for light doping grow continuously to be the spectra in the optimally doped region. This behavior significantly agrees with that of the angle-resolved photoemission spectroscopy spectra. Furthermore, the spin–orbit term and staggered transfer effectively induce a flux state, a pseudo-gap with time-reversal symmetry breaking. We have a nodal metallic state in the light-doping case since the pseudogap has a
dx2−y2 symmetry.
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Kazumasa Hattori, Satoshi Yotsuhashi, Kazumasa Miyake
2005 Volume 74 Issue 3 Pages
839-842
Published: March 15, 2005
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The aspect of the quasiparticle interaction of a local Fermi liquid, the impurity version of f
2-based heavy fermions, is studied by the Wilson numerical renormalization group method. In particular, the case of the f
2-singlet crystalline-electric-field ground state is investigated assuming the case of UPt
3 with the hexagonal symmetry. It is found that the interorbital interaction becomes larger than the intraorbital one in contrast to the case of the bare Coulomb interaction for the parameters relevant to UPt
3. This result offers us a basis to construct a microscopic theory of the superconductivity of UPt
3 where the interorbital interactions are expected to play important roles.
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Shoji Ishibashi, Hisashi Tanaka, Masanori Kohyama, Madoka Tokumoto, Ak ...
2005 Volume 74 Issue 3 Pages
843-846
Published: March 15, 2005
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We have investigated the electronic structure of Au(tmdt)
2 (tmdt = trimethylenetetrathiafulvalenedithiolate), which is a single-component conductor showing a magnetic phase transition around 100 K, by
ab initio plane-wave pseudopotential calculations. A single band crosses the Fermi level. This band and the next band below are a result of the strong hybridization between the two neighboring molecular levels near the Fermi level (SOMO and HOMO-1) and the system is more properly described as quarter-filled rather than half-filled in the strong correlation regime. The Fermi surface has corrugated-sheet-like parts nearly parallel to each other. Intraband generalized susceptibility suggests the presence of a nesting vector
a*⁄2 (
a* is one of the reciprocal lattice vectors). Spin-polarized calculation on the doubled unit cell along the
a axis (
a is a lattice vector) results in an antiferromagnetic order. The nesting is not perfect and Fermi-surface pockets remain in the magnetic phase. The implications of the present calculations with regard to experimental results are discussed.
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Yositake Takane
2005 Volume 74 Issue 3 Pages
847-850
Published: March 15, 2005
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Dynamical nucleation of a 2π-phase soliton in clean charge-density-wave (CDW) systems is studied using the Keldysh Green function technique within the quasiclassical approximation. We obtain a self-consistent solution for such dynamical nucleation and find that the 2π soliton can be nucleated without a large deviation from the equilibrium quasiparticle distribution. The nucleation induces the local shift δμ in the chemical potential. It is shown that δμ is determined by the distortion of the CDW phase outside the soliton core, and the order-parameter variation in the core region is not responsible for δμ. It is also shown that the magnitude of δμ is much smaller than a previous estimate.
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Naoyuki Katayama, Minoru Nohara, Fumiko Sakai, Hidenori Takagi
2005 Volume 74 Issue 3 Pages
851-854
Published: March 15, 2005
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Water-intercalated misfit-layer sulfides Na
x(H
2O)
y(
MS)
1+δ(TaS
2)
2 were found to exhibit superconductivity for
M=Sn, Pb, and Sb, as well as anhydrate sulfides (
MS)
1+δ(TaS
2)
2 with
M=Pb, Sb, and Bi. The optimal transition temperature
Tc was \\simeq3 K for the anhydrate sulfides, and was enhanced up to \\simeq4 K by intercalating a “bilayer” of water between the adjacent TaS
2 layers. This indicates that the presence of water molecule is favorable to superconductivity in the sulfides as in the cobalt oxide Na
xCoO
2·
nH
2O, for which superconductivity appears only for the “bilayer” hydrate.
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Hiroyuki Nakane, Gaku Motoyama, Takashi Nishioka, Noriaki K. Sato
2005 Volume 74 Issue 3 Pages
855-858
Published: March 15, 2005
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We measured the ac magnetic susceptibility of the ferromagnet UGe
2 that exhibits superconductivity at high pressures within a ferromagnetic phase. It is known that the ferromagnetic phase is separated into two phases and thus there are two critical pressures, namely,
PX∼12 kbar at which an unknown phase transition terminates and
PFM∼16 kbar at which a Curie temperature is suppressed to zero. We observed the following features in the vicinity of
PX: the discontinuity in the plot of superconducting transition temperature versus pressure, the maximum superconducting volume fraction in contrast to the small volume fraction near
PFM, and the markedly enhanced initial slope of the upper critical magnetic field (exceeding 200 kOe/K). These results indicate that the superconductivity directly correlates with
PX. We conclude therefore that it is the critical point
PX, rather than
PFM, that plays a crucial role in the appearance of the superconductivity.
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Masatoshi Imada
2005 Volume 74 Issue 3 Pages
859-862
Published: March 15, 2005
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The gas–liquid transition is a first-order transition terminating at a finite-temperature critical point with diverging density fluctuations. The Mott transition, a metal–insulator transition driven by Coulomb repulsion between electrons, has been identified with this textbook transition. However, the critical temperature of the Mott transition can be suppressed, leading to unusual quantum criticality, which results in a breakdown of the conventional Ginzburg–Landau–Wilson scheme. This accounts for non-Fermi-liquid-like properties, and strongly momentum-dependent quasiparticles as in many materials near the Mott insulator. Above all, the mode-coupling theory of the density fluctuations supports
d-wave superconductivity at the order of 100 K for the relevant parameters of copper oxide superconductors.
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Takehito Suzuki, Yuki Aikawa, Takuro Katsufuji
2005 Volume 74 Issue 3 Pages
863-866
Published: March 15, 2005
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We report the measurement of dielectric constant in ZnFe
2O
4 as a function of temperature and magnetic field. The behavior of dielectric constant for single crystals, which is dominated by the pair correlation of the neighboring Fe spins, indicates that ferromagnetic correlation is enhanced below 30 K, but is suppressed below 10 K, where positive magnetocapacitance is enhanced. It is also found that the magnetocapacitance of polycrystalline samples is much larger (∼10% at 14 T) than that of single crystals, because of the additional dielectric relaxation coupled with a uniform magnetization.
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Yoshihiko Ihara, Kenji Ishida, Chishiro Michioka, Masaki Kato, Kazuyos ...
2005 Volume 74 Issue 3 Pages
867-870
Published: March 15, 2005
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A weak magnetic order was found in a nonsuperconducting bilayered-hydrate Na
xCoO
2·
yH
2O sample by Co nuclear quadrupole resonance (NQR) measurement. The nuclear spin–lattice relaxation rate divided by temperature 1⁄
T1T shows a prominent peak at 5.5 K, below which a Co NQR peak splits due to an internal field at the Co site. From the analyses of the Co NQR spectrum at 1.5 K, the internal field is evaluated to be ∼300 Oe and found to be in the
ab-plane. The magnitude of the internal field suggests that the ordered moment is as small as ∼0.015μ
B using the hyperfine coupling constant reported previously. It is shown that the NQR frequency ν
Q correlates with magnetic fluctuations from measurements of NQR spectra and 1⁄
T1T in various samples. The higher-ν
Q sample has stronger magnetic fluctuations. A possible phase diagram for Na
xCoO
2·
yH
2O is depicted using
Tc and ν
Q, in which the crystal distortion along the
c-axis of the tilted CoO
2 octahedron is considered to be a physical parameter. Superconductivity with the highest
Tc is seemingly observed in the vicinity of a magnetic phase, suggesting strongly that magnetic fluctuations play an important role in the occurrence of superconductivity.
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Shunji Sugai, Nobuyuki Kaji, Akihito Osuka, Koshi Takenaka, Shigeru Ho ...
2005 Volume 74 Issue 3 Pages
871-874
Published: March 15, 2005
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Optical reflection spectroscopy perpendicular to the double-chain of PrBa
2Cu
4O
8 clarified that carriers in the plane transfer to the chain almost completely as temperature decreases from 295 to 150 K. Many anomalies around 150 K can be explained by the transfer of carriers. The temperature and Zn substitution effects suggest that the chains are in the Fermi liquid state when the carrier density is close to 0.5/Cu(1) and in the Tomonaga–Luttinger liquid state when the carrier density is 0.4/Cu(1).
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Norifumi L. Yamada, Takayoshi Takeda, Katsuya Kato, Michihiro Nagao, H ...
2005 Volume 74 Issue 3 Pages
875-877
Published: March 15, 2005
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We have investigated a static structure and membrane undulation in a swollen lamellar phase by small-angle neutron scattering and neutron spin echo (NSE). The effective viscosity, estimated by NSE data analysis using Zilman and Granek’s theory [Phys. Rev. Lett.
77 (1996) 4788], was larger than the bare viscosity of the solvent, and increased with decreasing lamellar repeat distance. A theory given by Gov
et al. [Phys. Rev. E
70 (2004) 011104] for hydrodynamics in confined fluid membranes could explain the tendency of NSE results. This indicates that the interference from neighbouring membranes neglected in Zilman and Granek’s theory should be considered in analyzing the membrane dynamics in the swollen lamellar phase from the NSE data.
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Atsunari Katsuki, Macoto Kikuchi, Noritaka Endo
2005 Volume 74 Issue 3 Pages
878-881
Published: March 15, 2005
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We observed the time evolution of dune fields in a water tank experiment and simulated it by using a simple model without taking complex fluid dynamics into account. The initial sand bed changed its form to transverse ripples, that is, dunes with straight crest lines perpendicular to the flow direction. Then crescentic dunes, called barchans, evolved from transverse ripples.
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Takeya Tsurumi
2005 Volume 74 Issue 3 Pages
883-895
Published: March 15, 2005
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The parametric down conversion of the light wave induced by stimulated polariton scattering in polar crystals is investigated from the aspect of long wave short wave interaction. Assuming that the light wave is the superposition of short wave (near-infrared light) and long wave (terahertz wave), time-evolution equations for the long wave and the envelope of the short wave are derived by means of a reductive perturbation method. Further, depending on the crystal properties, these equations describe two different situations. In one situation, the nonlinear effect of the short wave is dominant. In the other situation, the dispersion effect of the long wave is significant. For both cases, linear stability analysis is applied to the equations, and traveling wave solutions are obtained.
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E. V. Krishnan, Yan-ze Peng
2005 Volume 74 Issue 3 Pages
896-897
Published: March 15, 2005
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A solution for the new Hamiltonian amplitude equation is derived using a property of the reciprocal Weierstrass elliptic function. The Weierstrass elliptic function solution has been subsequently expressed in terms of the Jacobian elliptic function. The solitary wave solution which is the infinite period counterpart of the Jacobian elliptic function solution has also been derived.
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Zengo Tsuboi, Minoru Takahashi
2005 Volume 74 Issue 3 Pages
898-904
Published: March 15, 2005
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We propose a system of nonlinear integral equations (NLIE) which describes the thermodynamics of the
Uq(\\widehat
sl(
r+1)) Perk–Schultz model. These NLIE correspond to a trigonometric analogue of our previous result, and contain only
r unknown functions. In particular, they reduce to Takahashi’s NLIE for the
XXZ spin chain if
r=1. We also calculate the high temperature expansion of the free energy. In particular for
r=1 case, we have succeeded to derive the coefficients of order
O((\\frac
JT)
99).
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Hong-Bin Zhang, Li-Qun Chen
2005 Volume 74 Issue 3 Pages
905-909
Published: March 15, 2005
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In this paper, a unified form of Hojman’s conservation law and Lutzky’s one is derived. The conserved quantity is constructed in terms of a symmetry transformation vector of the equation of motion only. The Hojman’s conservation law and the Lutzky’s one may be regarded as two special cases of this unified form. A condition is deduced to exclude trivial conserved quantities. Two simple examples are presented to illustrate the applications of the results.
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Fam Le Kien, Victor I. Balykin, Kohzo Hakuta
2005 Volume 74 Issue 3 Pages
910-917
Published: March 15, 2005
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We calculate the optical potentials, i.e., the light shifts, of the ground and excited states of atomic cesium in a two-color evanescent field around a subwavelength-diameter fiber. We show that the light shifts of the 6
S1⁄2↔6
P3⁄2 transitions can be minimized by tuning one trapping light to around 934.5 nm in wavelength (central red-detuned magic wavelength) and the other light to around 685.5 nm in wavelength (central blue-detuned magic wavelength). The simultaneous use of the red- and blue-detuned magic wavelengths allows state-insensitive two-color trapping and guiding of cesium atoms along the thin fiber. Our results can be used to efficiently load a two-color dipole trap by cesium atoms from a magneto-optical trap and to perform continuous observations.
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Takao Wada, Toshiaki Kaneko
2005 Volume 74 Issue 3 Pages
918-923
Published: March 15, 2005
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We theoretically studied the
n-th multiple ionization cross section, σ
n (
n=1,2), of the C
60 fullerene in collisions with protons at impact energies of 150 keV to 2 MeV, on the basis of the impact-parameter dependent ionization probability per atom, in the independent-atom picture. The dependence of σ
n on the incident-beam direction was found, where the alignment of two carbon atoms is important. The present results are in better agreement with the recent experimental data, than the statistical energy deposition model.
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Yoichi Kurokawa, Hiroshi Miyazaki, Hideki T. Miyazaki, Yoji Jimba
2005 Volume 74 Issue 3 Pages
924-929
Published: March 15, 2005
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We have investigated the effect of a semi-infinite substrate on the eigenstates of two-dimensional periodically arrayed dielectric spheres on the basis of the internal electric field intensity distributions. The internal field intensity distributions clearly represent the features of each eigenstate, compared with transmission spectra and external near-field intensity distributions. A substrate with low dielectric constant hardly affects the optical properties of monolayer spheres. However, when the dielectric constant of the substrate exceeds a certain threshold, the field intensity of eigenstates drastically reduces. This behavior can be explained by energy dissipation into the substrate by opening of diffraction channels. Therefore, dips in transmission spectra become broader by interaction with the monolayer spheres and the substrate.
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Hisao Ashida, Hisaya Sugimoto, Hajime Sakakita
2005 Volume 74 Issue 3 Pages
930-940
Published: March 15, 2005
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Numerical simulations using magnetohydrodynamic (MHD) equations are performed for the pulsed poloidal current drive (PPCD) in reversed field pinch (RFP) plasmas. The PPCD is simulated by reducing the toroidal magnetic field at the wall,
Bz(
a), in the short period. The simulations take into account the values of reduced
Bz(
a), the period of changing
Bz(
a) and the start time as the characteristic parameters of the PPCD. The effects of the parameters on
m=1 resistive modes, which play the main role in the sustainment of RFP configurations, are calculated. The PPCD has stabilizing effect for the
m=1 modes over a wide range of the parameters. The dependence on the parameters for the formation of quasi-single helicity after the PPCD and for the growth of the
m=0 mode is calculated. The stabilizing factor due to the enhanced magnetic shear for the resistive modes is also analyzed by the linear growth rate in the equilibrium model of the transient configuration during the period of the PPCD.
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Mayuko Koga, Hayato Tsuchiya, Yoshinobu Kawai
2005 Volume 74 Issue 3 Pages
941-946
Published: March 15, 2005
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The effect of the boundary condition on chaotic behavior of the fluctuation observed in an electron cyclotron resonance plasma is investigated by chaos analysis using measured time series data. It is found that when a stainless cage of 290 mm in diameter and 500 mm in length is introduced in the chamber, the fluctuation changes from turbulent state to chaotic state in high microwave power region while it changes from chaotic state to periodic state in low microwave power region. This result suggests that the geometry of the cage affects the state of the instability. Moreover, it is found that the superposition of multicusped fields created by small permanent magnets reduces the chaotic dimension of the instability.
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Sanae-I. Itoh, Kimitaka Itoh, Masatoshi Yagi
2005 Volume 74 Issue 3 Pages
947-950
Published: March 15, 2005
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The stochastic trigger of the neoclassical tearing mode (NTM) in toroidal confinement plasmas by the background turbulence is studied. The life time is given by the inverse of the statistical average of transition rate. On the basis of the statistical theory of a plasma turbulence, the life time of the state free from the NTM is obtained. The dependence on the plasma parameters is explicitly shown. The beta limit by the NTM is found to be diffused. This gives a new insight for the database of operational boundary of toroidal plasmas.
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Shonosuke Ohta, Makiko Inoue
2005 Volume 74 Issue 3 Pages
951-954
Published: March 15, 2005
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A new fractal dimension of diffusion-limited aggregation (DLA) is studied by tip front angle near hottest branch projecting bare field, which is obtained from envelope line considering near pentagonal symmetry of DLA. The angle changes largely along cluster growth, and the mean shows 106.2° for 10
5 N=3×10
6 clusters. From application of wedge model, tip front dimension is obtained as
Dt=1.709. Asymptotic fractal dimension
Dt=1.710 can be estimated consistently with usual box and gyration dimensions from 25
N=2×10
8 clusters.
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Masashi Torikai, Mamoru Yamashita
2005 Volume 74 Issue 3 Pages
955-959
Published: March 15, 2005
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McMillan liquid crystal model sandwiched between strong homeotropic anchoring walls is studied. Phase transitions between isotropic, nematic, and smectic A phases are investigated for wide ranges of an interaction parameter and of the system thickness. It is confirmed that the anchoring walls induce an increase in transition temperatures, dissappearance of phase transitions, and an appearance of non-spontaneous nematic phase. The similarity between influence of anchoring walls and that of external fields is discussed.
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Yuriy P. Monarkha, Kimitoshi Kono
2005 Volume 74 Issue 3 Pages
960-969
Published: March 15, 2005
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The theory of nonlinear conductivity of the 2D Wigner solid (WS) formed on the surface of normal and superfluid
3He is presented. We show that extremely strong damping of the Fermi-liquid
3He greatly affects the dimple sublattice of surface displacements moving along with the WS, which induces the nonlinear conductivity of surface electrons long before the conventional Bragg–Cherenkov condition is achieved. Both the hydrodynamic and long mean-free-path regimes are considered in order to find the velocity induced transformation of the dimple sublattice and field–velocity characteristics of the WS. Depending on the regime of measurement the theory describes dynamic decoupling of the WS from surface dimples, or the field–velocity characteristics which has regions with negative differential conductivity.
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Hidekazu Okamura, Toshihisa Koretsune, Shin-ichi Kimura, Takao Nanba, ...
2005 Volume 74 Issue 3 Pages
970-974
Published: March 15, 2005
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Infrared magnetic circular dichloism (MCD), or equivalently magneto-optical Kerr effect, has been measured on the Tl
2Mn
2O
7 pyrochlore, which is well known for exhibiting a large magnetoresistance around the Curie temperature
TC∼120 K. A circularly polarized, infrared synchrotron radiation is used as the light source. A pronounced MCD signal is observed exactly at the plasma edge of the reflectivity near and below
TC. However, contrary to the conventional behavior of MCD for ferromagnets, the observed MCD of Tl
2Mn
2O
7 grows with the applied magnetic field, and not scaled with the internal magnetization. It is shown that these results can be basically understood in terms of a classical magnetoplasma resonance. The absence of a magnetization-scaled MCD indicates a weak spin–orbit coupling of the carriers in Tl
2Mn
2O
7. We discuss the present results in terms of the microscopic electronic structures of Tl
2Mn
2O
7.
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Gen’ya Sakurai, Yoshio Kuramoto
2005 Volume 74 Issue 3 Pages
975-982
Published: March 15, 2005
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Multipolar interactions are derived in the orbitally degenerate Anderson lattice with a spherical Fermi surface and one conduction electron per unit cell of the simple cubic lattice. As the crystalline-electric-field (CEF) ground state of
f1 configuration, the four-fold degenerate Γ
8 is mainly studied. Intersite interactions up to a sufficiently distant pair are Fourier transformed to the wavenumber space. For the Γ
8 case, quadrupolar and octupolar interactions favor the staggered order with
q=(1⁄2,1⁄2,1⁄2), while the dipolar interaction favors an incommensurate magnetic structure with a long modulation period.The latter is due to a Kohn anomaly which is found to be sharply peaked for interaction channels with large angular momenta. Implications of results are discussed for multipole orders in CeB
6, and the incommensurate magnetic structure in a quasi-cubic system CeB
2C
2.
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Muneo Sugiura, Masahisa Tsuchiizu, Yoshikazu Suzumura
2005 Volume 74 Issue 3 Pages
983-987
Published: March 15, 2005
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We examine the transition temperature of spin-Peierls state,
TSP, in the one-dimensional quarter-filled Peierls–Hubbard model with lattice dimerization and intersite repulsive interaction,
V, by applying the bosonization and the renormalization-group method. It is shown that for large
V the transition temperature
TSP is suppressed due to the appearance of the charge ordering. In the spin-Peierls state, the location of the spin-singlet state is shifted continuously from the bond of the lattice to the on-site by the increase of the charge ordering. The result is compatible with our previous results of the ground state. We discuss the pressure effect on
TSP, which has been observed in the NMR measurement.
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Akira Oguri, A. C. Hewson
2005 Volume 74 Issue 3 Pages
988-996
Published: March 15, 2005
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We study the low-energy properties of a Hubbard chain of finite size
NC connected to two noninteracting leads using the numerical renormalization group (NRG) method. The results obtained for
NC=3 and 4 show that the low-lying eigenstates have one-to-one correspondence with the free quasi-particle excitations of a local Fermi liquid. It enables us to determine the transport coefficients from the fixed-point Hamiltonian. At half-filling, the conductance for even
NC decreases exponentially with increasing
U showing a tendency towards the development of a Mott–Hubbard gap. In contrast, for odd
NC, the Fermi-liquid nature of the low-energy states assures perfect transmission through the Kondo resonance. Our formulation to deduce the conductance from the fixed-point energy levels can be applied to various types of interacting systems.
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Hiroshi Akera, Hidekatsu Suzuura
2005 Volume 74 Issue 3 Pages
997-1005
Published: March 15, 2005
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A theory of thermohydrodynamics in two-dimensional electron systems in quantizing magnetic fields is developed including a nonlinear transport regime. Spatio-temporal variations of the electron temperature and the chemical potential in the local equilibrium are described by the equations of conservation with the number and thermal-energy flux densities. A model of these flux densities due to hopping and drift processes is introduced for a random potential varying slowly compared to both the magnetic length and the phase coherence length. The flux measured in the standard transport experiment is derived and is used to define a transport component of the flux density. The equations of conservation can be written in terms of the transport component only. As an illustration, the theory is applied to the Ettingshausen effect, in which a one-dimensional spatial variation of the electron temperature is produced perpendicular to the current.
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Hitoshi Okamoto, Yoshiyuki Ono
2005 Volume 74 Issue 3 Pages
1006-1013
Published: March 15, 2005
Released on J-STAGE: December 06, 2007
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The static and dynamical behaviors of an acoustic polaron in a quasi-one-dimensional branching-off system are studied numerically by employing Su–Schrieffer–Heeger’s model extended to involve the branching-off structure. At the branching-off site, an electron is found to feel an attractive potential with the strength equal to the transfer integral between one-dimensional neighboring sites. When an acoustic polaron prepared at a site sufficiently apart from the branching-off site is set in motion by an external force towards the branching site, it is totally reflected, totally trapped or partially reflected and partially trapped at the branching site, depending on the extent of the polaron just before it reaches the branching site. It is argued that this behavior is essentially the same as that seen in a one-dimensional system with a single-site-type attractive potential. When the effective attractive potential at the branching site is cancelled out by a real repulsive site-potential, the polaron moving to that site is found to be able to go through that site.
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Petre Badica, Takaaki Kondo, Kazumasa Togano
2005 Volume 74 Issue 3 Pages
1014-1019
Published: March 15, 2005
Released on J-STAGE: December 06, 2007
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Recently we have found superconductivity in a cubic antiperovskite-like compound Li
2BPd
3. A new pseudo-binary complete solid solution Li
2B(Pd
1−xPt
x)
3,
x=0–1 with similar structure has been synthesized and observation of superconductivity in the entire
x-range is reported. Our results strongly suggest that superconductivity is of bulk type. Critical temperature
Tc is decreasing approximately linearly with amount (
x) of Pt from 7.2–8 K for Li
2BPd
3 to 2.2–2.8 K for Li
2BPt
3. From isothermal magnetization (
M–
H) measurements, lower critical fields
Hc1 (138 Oe/
x=0, 38 Oe/
x=1), upper critical fields
Hc2WHH (3.4 T/
x=0, 1 T/
x=1), coherence length ξ(0) (9.8 nm/
x=0, 17.9 nm/
x=1) and penetration depth λ(0) (190 nm/
x=0, 364 nm
x=1) were estimated and shown to follow approximately linear dependencies with
x, either. Structure and superconducting similarities with MgCNi
3, viewed as a bridge between low and high
Tc superconductors are increasing the expectations that Li
2B(Pd
1−xPt
x)
3,
x=0–1 superconductor can be included in the same class of ‘intermediate’ superconductors. For
x=0–1 a weak fish-tail effect was observed at low and intermediate fields. Apart from this effect, some samples for
x=1 have shown magnetization jumps at fields close to
Hc2.
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Hirohiko Ichikawa, Luna Kano, Masahiro Saitoh, Shin Miyahara, Nobuo Fu ...
2005 Volume 74 Issue 3 Pages
1020-1025
Published: March 15, 2005
Released on J-STAGE: December 06, 2007
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We have observed the orbital ordering in the ferromagnetic Mott-insulator Lu
2V
2O
7 by the polarized neutron diffraction technique. The orbital ordering pattern determined from the observed magnetic form factors can be explained in terms of a linear combination of wave functions |
yz〉, |
zx〉 and |
xy〉; | 0 〉& = \\sqrt\\frac13| xy 〉+ \\sqrt\\frac13| yz 〉+ \\sqrt\\frac13| zx 〉
& ∝| (x+y+z)^2-r^2 〉, where each orbital is extended toward the center-of-mass of the V tetrahedron. We discuss the stability of the ferromagnetic Lu
2V
2O
7, using a Hubbard Hamiltonian with these three orbitals.
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Chihiro Kato, Satoshi Iikubo, Minoru Soda, Masatoshi Sato, Kazuhisa Ka ...
2005 Volume 74 Issue 3 Pages
1026-1029
Published: March 15, 2005
Released on J-STAGE: December 06, 2007
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Magnetic behavior of Sr
2MnO
3.5 has been studied by measuring the magnetic susceptibility χ, high-field magnetization and specific heat
C. The spin structure has also been studied by means of the powder neutron diffraction. The system has the two-dimensional linkage of corner-sharing MnO
5 pyramids derived by regularly reducing the oxygen atoms from the MnO
2 layers of Sr
2MnO
4. The oxygen shared by two neighboring pyramids belongs, in one case, to the basal planes of both pyramids, or in another case, to the basal plane of one pyramid and the apex of another one. Due to the existence of these two kinds of the bridging oxygens, it provides a quite characteristic example of moment systems with ferromagnetic (F) clusters of four Mn
3+ moments, which are interacting with the neighboring clusters in the antiferromagnetic (AF) way. The results of the studies are as follows. The Neel temperature
TN is 126 K. The exchange interactions corresponding to the two kinds of the bridging oxygens are estimated by the high temperature expansion method to be −50.9 K (AF) and 18.7 K (F), where the signs are in agreement with our expectation. The magnetic structure is consistent with the picture of interacting clusters, though the F-interaction is weaker than the AF one. It is collinear AF one with the moments along the
b axis.
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Kazuyuki Matsuhira, Yoshihiro Doi, Makoto Wakeshima, Yukio Hinatsu, Hi ...
2005 Volume 74 Issue 3 Pages
1030-1035
Published: March 15, 2005
Released on J-STAGE: December 06, 2007
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Sm-based filled skutterudite phosphides SmFe
4P
12, SmRu
4P
12 and SmOs
4P
12 synthesized at high temperatures and high pressures have been studied by specific heat measurements in magnetic fields. SmFe
4P
12 shows an anomaly at 1.6 K attributed to a ferromagnetic transition. SmRu
4P
12 shows a metal–insulator transition at 16 K. This transition consists of two successive transitions, which suggests orbital and antiferromagnetic orderings. SmOs
4P
12 shows a sharp anomaly at 4.5 K due to an antiferromagnetic ordering. We discuss the characteristic behavior of those phase transitions and the crystalline electric field state in Sm
T4P
12 (
T=Fe, Ru and Os). Interestingly, the magnetic entropy of SmFe
4P
12 have only 0.16
Rln2 below the ferromagnetic ordering temperature. This suggests a strong spin fluctuation effect. On the other hand, the variation of magnetic entropy in SmRu
4P
12 and SmOs
4P
12 reaches to nearly
Rln4 below the ordering temperature.
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Susumu Matsuo, Hiroshi Nakano, Senni Motomura, Tsutomu Ishimasa
2005 Volume 74 Issue 3 Pages
1036-1043
Published: March 15, 2005
Released on J-STAGE: December 06, 2007
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A simple arithmetic rule is proposed to correlate the matching rule in Penrose lattice with long-range Ising spin orders with the aim of clarifying the energetic mechanism of the orders under Ruderman–Kittel–Kasuya–Yoshida-like (RKKY) alternating interactions. Three different types of antiferromagnetic orders were found to be compatible with the rule. The orders showed sharp magnetic diffraction spots with the same peak widths as the ordinary lattice diffraction, which were consistent with the long-range orders enforced by the matching rule. The three types of the orders were most adequately interpreted as the orders in the occupation domain in the phason space. The RKKY interactions resulted in two of the orders in simulated annealing calculations. The results indicate the importance in the energetic mechanism of the
consistency of the connectivity of the interaction signs inherent in the quasiperiodic structure.
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Takenao Shinohara, Masayuki Shigemune, Tetsuya Sato, Tomoyasu Taniyama ...
2005 Volume 74 Issue 3 Pages
1044-1048
Published: March 15, 2005
Released on J-STAGE: December 06, 2007
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X-ray magnetic circular dichroism (XMCD) of Pd
97.1Fe
2.9 fine particle samples is studied at the Pd
L2,3 edges. The magnetic moment of a Pd atom, which is estimated using the magneto-optical sum rule, is ∼0.06μ
B/atom independent of particle size, while the total magnetization of the particle samples decreases monotonically with decreasing particle size. We attribute the size dependent magnetization to a reduction in the Fe magnetic moment at the surface region with decreasing particle size. Analysis of the XMCD data is reported in detail.
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Hoang Ngoc Cam
2005 Volume 74 Issue 3 Pages
1049-1066
Published: March 15, 2005
Released on J-STAGE: December 06, 2007
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Exciton–boson formalism approach to the description of two-pair correlations in the electron–hole system in laser-excited direct semiconductors is proposed. The spin of quasiparticles is properly included by group-theoretical rules. On the example of the system of heavy hole excitons in quantum wells it is shown that two-pair Coulomb correlations consist of two components: effective repusion between excitons with nonzero total spin and attraction between excitons with zero total spin. The latter component is behind the biexciton formation and its coupling to excitons. In application to the study of coherent four-wave-mixing (FWM) it is established that the two components generate FWM respectively in the co-circular and cross-linear polarizations, and jointly in the collinear polarization. General expressions are derived for the amplitude of the FWM signal in the polarization configurations yielding analytical results in the ultrashort pulses limit. Refined by computations taking pulses temporal evolution into consideration, these results provide an adequate description of biexciton effects and the polarization dependence of coherent FWM in quantum wells.
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Kiyotaka Hammura, Kazuo Sakai
2005 Volume 74 Issue 3 Pages
1067-1070
Published: March 15, 2005
Released on J-STAGE: December 06, 2007
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The magneto-oscillatory spectra in cuprous oxide can be interpreted as reflecting classical non-integrability of the Hamiltonian of an electron–hole pair generated by the incident light in magnetic fields. The spectra have multi-oscillatory structure, and three periods are extracted from the spectra. It is found that the three periods coincide with three
recurrence periods associated with corresponding three types of unstable classical trajectories. The instability is due to non-integrability of the system with spherical Coulomb and planar diamagneticpotential of magnetic fields. This type of analysis opens the way to get an evidence of “quantum chaos” in solid state.
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Atsushi Kamimura, Satoshi Yukawa, Nobuyasu Ito
2005 Volume 74 Issue 3 Pages
1071-1072
Published: March 15, 2005
Released on J-STAGE: December 06, 2007
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Hideki Nishio, Takeshi Shinohara, Shuichiro Anzai, Fumihiko Wagatsuma, ...
2005 Volume 74 Issue 3 Pages
1073-1074
Published: March 15, 2005
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Kaoru Eguchi, Yutaka Kawabe, Eiichi Hanamura
2005 Volume 74 Issue 3 Pages
1075-1076
Published: March 15, 2005
Released on J-STAGE: December 06, 2007
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Toyohiko Kinoshita, Takanori Wakita, HaiLin Sun, Takahide Tohyama, Ayu ...
2005 Volume 74 Issue 3 Pages
1077
Published: March 15, 2005
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Yuji Aoki, Hitoshi Sugawara, Hisatomo Harima, Hideyuki Sato
2005 Volume 74 Issue 3 Pages
1078
Published: March 15, 2005
Released on J-STAGE: December 06, 2007
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