-
Tomohiro Sasamoto, Miki Wadati
専門分野: Mathematical methods in physics.
1997 年 66 巻 2 号 p.
279-282
発行日: 1997/02/01
公開日: 1999/10/01
ジャーナル
認証あり
A new type of dynamic matrix product ansatz is proposed. The stateswhich satisfy the “imaginary time” Schrödinger equationare represented in the form of products of time-dependent and time-independent matrices.From the algebra among the matrices, the Bethe ansatz equation is derived for the asymmetric exclusion process andthe XXZ spin chain under the periodic boundary condition.
抄録全体を表示
-
Ryogo Hirota
専門分野: Mathematical methods in physics.
1997 年 66 巻 2 号 p.
283-284
発行日: 1997/02/01
公開日: 1999/10/01
ジャーナル
認証あり
A “random-time Toda equation” is obtained by replacing the time interval of the discrete-time Toda equation by random variables. The random-time Toda equation has higher-order conserved quantities in spite of the randomness introduced into the equation. Also obtained are the higher-order conserved quantities of a class of “random-time soliton equations” which are related to the random-time Toda equation via Miura transformations.
抄録全体を表示
-
Masanori Kidera, Masumi Oshima, Yuichi Hatsukawa, Kazuyoshi Furutaka, ...
専門分野: Nuclear structure.
1997 年 66 巻 2 号 p.
285-287
発行日: 1997/02/01
公開日: 1999/10/01
ジャーナル
認証あり
The high-spin states of
155Gd were investigated by means of multiple Coulomb excitation with a 390-MeV
90Zr beam. The members of the ground-state rotational band of
155Gd were assigned up to (31/2
-).The members of a positive-parity side band were also strongly excited up to high spins (33/2
+) with populations comparable to those of ground-band members.The experimental population is compared with Coulomb-excitation calculations taking account of the recommended upper limits for E1 and E3 strengths compiled in the whole mass region.It turns out that an E1 and/or an E3 strength larger than those limits would be necessary to account for the experiment.
抄録全体を表示
-
Yoshiomi Kondoh, Masanori Yamaguchi, Katsuhisa Yokozuka
専門分野: The physics of plasmas and electric discharges.
1997 年 66 巻 2 号 p.
288-290
発行日: 1997/02/01
公開日: 1999/10/01
ジャーナル
認証あり
It is shown by three-dimensional magnetohydrodynamic simulations that the toroidal current J
z can be induced by a process of relaxation without helicity invariance under a condition of no external magnetic helicity injection.It is shown that the magnetic helicity is induced during relaxation and it ispassively determined as a result of the time evolution of the dynamicalsystem. Numerical results suggest thatthe basic process for the toroidal current drive duringrelaxation is the nonlinear energy transfer fromthe toroidal to the poloidal magnetic energy with the intervention of the kinetic energy.It is demonstrated that self-organization to the lower eigenmode with a larger-scale structureoccurs during relaxation.
抄録全体を表示
-
Kenichiro Yagi, Kenji Ohwada, Hikaru Terauchi
専門分野: Equations of state, phase equilibria, and phase transitions.
1997 年 66 巻 2 号 p.
291-293
発行日: 1997/02/01
公開日: 1999/10/01
ジャーナル
認証あり
An X-ray diffraction study of KBr
0.64(NO
2)
0.36 was performed to elucidate its structural glass-like properties and compare them to those of other mixed crystals. As the temperature decreases, the fundamental Bragg reflections begin to decrease and strong diffused scattering appears around the Brillouin-zone center of an face centered cubic (fcc) lattice, Γ-point. The results indicate that the local distortion of a lattice with only short-range ferroelectric correlation is induced by reorientational freezing of nitrite ions. The correlation length estimated from the diffused scattering is about 23, Å at 100, K, which is much smaller than the coherence length of an X-ray.
抄録全体を表示
-
Takeshi Nakanishi, Kunihiko Yamaji, Takashi Yanagisawa
専門分野: Electron states in condensed matter.
1997 年 66 巻 2 号 p.
294-297
発行日: 1997/02/01
公開日: 1999/10/01
ジャーナル
認証あり
The possibility of superconductivity in the ground state of thetwo-dimensional Hubbard model was investigated by means of thevariational Monte Carlo method. With slight hole doping on the 6 × 6 and 10 × 10 lattices, a clear minimum was obtained onthe curve of the total energy versus the amplitude of the d-wave gapfunction for large on-site Coulomb energies. Superconducting paircorrelations were observed to be well developed. The-next-nearest-neighbor transfer was found to appreciably affect theminimum depth.
抄録全体を表示
-
Fumio Komori, Takao Iwaki, Ken Hattori, Osamu Shiino, Tetsuya Hasegawa
専門分野: Electron states in condensed matter.
1997 年 66 巻 2 号 p.
298-301
発行日: 1997/02/01
公開日: 1999/10/01
ジャーナル
認証あり
The atomic structure and tunneling spectra of a cleaved surface of a 2H-NbSe
2 single crystal were studied by scanning tunneling microscopy at 4.2 K. Small domains with √13 × √13 modulation were found adjacent to the flatsurface with a 3 × 3 intrinsic charge density wave (CDW). The surface atom arrangement in the domains is the same as that in the 2H-type surface.The density of states around the Fermi energy was measured at the domains by tunneling spectroscopy, and found to be lower than that at the 2H-type surface. The √13 × √13 modulation is considered to originate from another CDW, which can be expected to occur in 4H-NbSe
2 clusters buried in a 2H-type crystal. The change of the tunneling spectrum across the boundary between the 2H-typesurface and a √13 × √13 modulated domain was also measured, and the proximity of superconductivity of 2H type to the modulated domain is discussed.
抄録全体を表示
-
Yasuhide Tomioka, Atsushi Asamitsu, Hideki Kuwahara, Yoshinori Tokura
専門分野: Electron states in condensed matter.
1997 年 66 巻 2 号 p.
302-305
発行日: 1997/02/01
公開日: 1999/10/01
ジャーナル
認証あり
The stability of the charge-ordered state against variations of temperature (T) and external magnetic field (H) has been investigated for Pr
0.65(Ca
1-ySr
y)
0.35MnO
3 crystals with controlled one-electron bandwidth. For y=0.3, the charge- and orbital-ordering appears below 200, K as in the y<0.3 crystals, but collapses into the metallic state below 100, K. Under a magnetic field, such a reentrant feature is observed in a wider region of y (<0.3). A variation of the H-T phase diagram for the charge-ordered state with the one-electron bandwidth is presented in view of the origin of the colossal magnetoresistance.
抄録全体を表示
-
Yasuo Y. Suzuki
専門分野: Electronic transport in condensed matter.
1997 年 66 巻 2 号 p.
306-309
発行日: 1997/02/01
公開日: 1999/10/01
ジャーナル
認証あり
We examine a narrow-band Holstein--Hubbard model where electrons arecoupled to a local lattice distortion and form small polarons. Whenthe on-site Coulomb interactions are overscreened by strongelectron--phonon coupling, the polarons attract each other through theeffective potential, bind into pairs, and form small bipolarons. Theoptical conductivity of small bipolaron is calculated as afunction of frequency, electron density, and temperature, within alimited temperature and parameter range.
抄録全体を表示
-
Eiji Ohmichi, Hiroshi Ito, Takehiko Ishiguro, Tokutaro Komatsu, Gunzi ...
専門分野: Electronic transport in condensed matter.
1997 年 66 巻 2 号 p.
310-313
発行日: 1997/02/01
公開日: 1999/10/01
ジャーナル
認証あり
The electronic structures of κ-type and κ'-type (BEDT-TTF)_2Cu_2(CN)_3 exhibiting semiconducting and superconducting behavior at ambient pressure, respectively, were investigated through a high-field magnetoresistance measurement under pressure. The Shubnikov-de Haas signal was invisible in both salts. The angle-dependent magnetoresistance oscillation (AMRO) was found in the κ-type salt, while the AMRO was not found in the κ'-type salt. The implication and origin of this difference are discussed.
抄録全体を表示
-
Tomi Ohtsuki, Toru Kawarabayashi
専門分野: Electronic transport in condensed matter.
1997 年 66 巻 2 号 p.
314-317
発行日: 1997/02/01
公開日: 1999/10/01
ジャーナル
認証あり
Diffusion of electrons in three-dimensional disordered systems is investigated numerically for all three universality classes, namely, orthogonal, unitary and symplectic ensembles. The second moment of the wave packet ‹ r
2(t)› at the Anderson transition is shown to behave as -- t
a(a≈ 2/3). From the temporal autocorrelation function C(t), the fractal dimension D
2 is deduced, which is almost half the value of the space dimension for all of the universality classes.
抄録全体を表示
-
Akihisa Koizumi, Nobuhiko Sakai, Nobuya Shirai, Masami Ando
専門分野: Magnetic properties and materials.
1997 年 66 巻 2 号 p.
318-321
発行日: 1997/02/01
公開日: 1999/10/01
ジャーナル
認証あり
A pulse magnet is applied to an experiment on magnetic Compton scattering using circularly polarized synchrotron-radiation X-rays. The sample is c-axis oriented SmCo
5, which is known to be a hard magnetic materials. Consecutive pulsed magnetic fields of 11.7, tesla are used to repeatedly reverse the magnetization direction of the sample. The measurement is done with residual magnetization of the sample at room temperature. The magnetic Compton profile is found to be well-reproduced by a combination of a theoretical Sm-4f profile and an experimental Co profile. On the assumption that the Co spin moment in the hexagonal symmetry is 1.56μ
B, the Sm-4f spin moment is evaluated to be -1.79μ
B which is quite small compared with the expected spin moment 3.57μ
B for the Sm ground state (J=5/2 M
J=5/2). This experiment suggests for the first time the feasibility of using pulse magnets for X-ray magnetic scattering and absorption measurements on hard magnetic materials.
抄録全体を表示
-
Osamu Koseki, Fumitaka Matsubara
専門分野: Magnetic properties and materials.
1997 年 66 巻 2 号 p.
322-325
発行日: 1997/02/01
公開日: 1999/10/01
ジャーナル
認証あり
We have proposed a cluster heat bath (CHB) method of a quasi-one-dimensional Ising model and demonstrated that it reproduces the exact results of the two-dimensional Ising model with axially anisotropic exchange interactions. The key point of this method is to select one of the equilibrium spin configurations of each of the chains which are subjected to effective fields of surrounding spins. Thus, the chains are always in their equilibrium state during the simulation, and the d-dimensional model effectively becomes a (d-1)-dimensional model of fictitious spins with their freedom of 2N, where N is the number of the spins on the chain, and the simulation time is drastically reduced.
抄録全体を表示
-
Yasuhiko Fujii, Hironori Nakao, Tomoyuki Yosihama, Masakazu Nishi, Ken ...
専門分野: Magnetic properties and materials.
1997 年 66 巻 2 号 p.
326-329
発行日: 1997/02/01
公開日: 1999/10/01
ジャーナル
認証あり
In this letter we report lattice dimerization and spin-gap formation of NaV
2O
5 below its spin-Peierls transition temperature T
sp=35.3, K, in which there are V
4+ (S=1/2) linear chains along the b axis of its orthorhombic structure. A single-crystal X-ray scattering experiment shows superlattice reflections with a lattice modulation vector q=(1/2, , 1/2, , 1/4). Inelastic neutron scattering from a powder sample at T=7, K clearly demonstrates a gap energy of 9.8, meV at a scattering vector |Q|=1.0, Å
-1 corresponding to the reciprocal lattice point (1, , 1/2, , 0).
抄録全体を表示
-
Kazuo Hida
専門分野: Magnetic properties and materials.
1997 年 66 巻 2 号 p.
330-333
発行日: 1997/02/01
公開日: 1999/10/01
ジャーナル
認証あり
The low energy properties of the spin-1/2 random Heisenberg chain with ferromagnetic and antiferromagnetic interactions are studied by means of the density matrix renormalization group (DMRG) and real space renormalization group (RSRG) method for finite chains. The results of the two methods are consistent with each other. The deviation of the gap distribution from that of the random singlet phase and the formation of the large-spin state is observed even for relatively small systems. For a small fraction of the ferromagnetic bond, the effect of the crossover to the random singlet phase on the low temperature susceptibility and specific heat is discussed. The crossover concentration of the ferromagnetic bond is estimated from the numerical data.
抄録全体を表示
-
Yutaka Itoh, Hiroshi Yasuoka
専門分野: Magnetics resonances and relaxations in condensed matter; MÖssbauer effect.
1997 年 66 巻 2 号 p.
334-336
発行日: 1997/02/01
公開日: 1999/10/01
ジャーナル
認証あり
We present an experimental magnetic phase diagram based on two spin-gaps (a dynamical spin gap Δ
R estimated from nuclear spin-lattice relaxation rate 1/T
1 and a static one Δ
S estimated from static uniform spin susceptibility χ
s) for low-dimensional quantum spin systems: one-dimensional (1D) Haldane gap, two-leg spin ladder, dimer spin, 2D plaquette spin, and high-T
c Cu oxide systems. Possible universal correlation for respective materials and their mutual relations are discussed.
抄録全体を表示
-
Hiroshi Matsuyama, Isao Harada, Akio Kotani
専門分野: Optical properties and condensedmatter spectroscopy and other interactions of matter with particles and radiation.
1997 年 66 巻 2 号 p.
337-340
発行日: 1997/02/01
公開日: 1999/10/01
ジャーナル
認証あり
The systematic trend in magnetic circular X-ray dichroism (MCXD) at the L
2, 3 edges for various rare-earth elements is studied by taking into account the effects of the 4f-5d exchange interaction on the electric-dipole transition from the 2p core state to the outermost 5d state. The exchange interaction gives rise to, in addition to the usual polarization effect on the 5d ground state, a novel effect of contraction in the radial part of the 5d orbits concerned. It is pointed out that, especially the latter effect, which leads to the enhancement of the transition dipole matrix element depending on the spin and the orbital momenta of the 5d state, plays a crucial role in successfully interpreting the experimental results observed. Quadrupole contributions just below the edges are also discussed.
抄録全体を表示
-
Kozo Okada, Akio Kotani
専門分野: Optical properties and condensedmatter spectroscopy and other interactions of matter with particles and radiation.
1997 年 66 巻 2 号 p.
341-344
発行日: 1997/02/01
公開日: 1999/10/01
ジャーナル
認証あり
Intersite Coulomb interaction between Cu 3d and O 2p holes (U
pd) isshown to be important in analyzing the optical conductivityand the Cu 2p core-level X-ray photoemission spectrum (XPS) ofone-dimensional copper oxides such as Ca
2CuO
3 and Sr
2CuO
3 consistently.It is shown that the Cu 2p XPS is rather insensitive to U
pd, while the optical gap is expanded by stronger U
pd.With U
pd around 2 eV, the superexchange coupling constant of Cu 3dspins is also reasonably reproduced.The influence on the Cu 2p XPS of the intersite Coulomb potential ofthe Cu 2p hole acting on the neighboring O 2p holes is also discussed.
抄録全体を表示
-
Hideaki Ujino, Miki Wadati
専門分野: Mathematical methods in physics.
1997 年 66 巻 2 号 p.
345-350
発行日: 1997/02/01
公開日: 1999/10/01
ジャーナル
認証あり
Orthogonality of the Hi-Jack polynomials, which were introduced asthe simultaneous eigenfunctions of the first and second conserved operatorsof the Calogero model, is proved by showing that they are non-degeneratesimultaneous eigenfunctions for all the commuting conserved operators ofthe Calogero model.The fact that our definition of the Hi-Jack polynomials uniquely specifiesthe Hi-Jack polynomials, which is assured by the triangularity withrespect to the dominance order among the Young tableaux, plays an essential role in our proof.
抄録全体を表示
-
Hiroshi Natori, Tomo Munehisa
専門分野: Classical and quantum physics: mechanics and fields.
1997 年 66 巻 2 号 p.
351-359
発行日: 1997/02/01
公開日: 1999/10/01
ジャーナル
認証あり
We study algorithm to calculate the time dependent Schrödinger equation numerically and to visualize the results. We extend the product formula by the Trotter-Suzuki decomposition to cases of Hamiltonians with vector potentials. This method is unconditionally stable and it can be used for a time dependent Hamiltonian so that one can apply it to various problems without any difficulty. After examining numerical errors for time evolutions of one dimensional wave packets, we present the errors under a constant magnetic field. Also we discuss a cyclotron motion in quantum mechanics, where an advantage for the unconditional stability is demonstrated. In order to visualize the results we make animations of the time evolutions, where the phase of the wave function is represented by colors and its absolute value is shown by brightness. Here we suggest a new way to represent a complex number by colors.
抄録全体を表示
-
Tetsuhiko Chikyu
専門分野: Statistical physics and thermodynamics.
1997 年 66 巻 2 号 p.
360-366
発行日: 1997/02/01
公開日: 1999/10/01
ジャーナル
認証あり
Damage spreading phenomena are defined artificially in the dynamics of the Ising spin systems in computer simulation. Random numbers used in computer simulations play a role to evolve the system to thermal equilibrium states. When the dynamics is taken not only as an artificial tool which realizes an equilibrium state but also as some physical process, damage spreading phenomena can be interpreted as physical objects. It is a main aim to give a concrete physical image to damage spreading phenomena which is artificially defined in original. Key property is a response for thermal noise by the interaction with a heat bath. Damage spreading as a phenomenon in time series is related with a spatial property in the percolation image of the Ising model by interpreting the Fortuin-Kasteleyn representation as a percolation image of the Ising models. This time-space relation reveals the essence of damage spreading as critical phenomena in physical systems.
抄録全体を表示
-
Jun–ichi Ueda, Yoshiro Sadamoto
専門分野: Mechanics, elasticity, and rheology.
1997 年 66 巻 2 号 p.
367-368
発行日: 1997/02/01
公開日: 1999/10/01
ジャーナル
認証あり
The effective mass of spring is experimentally investigated by measuring the spring constant K, the spring mass m, the suspended mass M, and the oscillation period T. It is found that, as the mass ratio M/m increases beyond 7, the effective mass m
* of spring, defined by T
2=4π
2(M+m
*)/K, becomes smaller than Rayleigh's value m/3 and eventually reaches negative values. This unexpected behavior of the effective mass seems to be explainable in terms of the elastic after-effect.
抄録全体を表示
-
Yasumasa Ookouchi, Toru Hada
専門分野: Fluid dynamics.
1997 年 66 巻 2 号 p.
369-378
発行日: 1997/02/01
公開日: 1999/10/01
ジャーナル
認証あり
In this report, a modified Lorenz system is introduced for describing convective motion heated from below with a sinusoidal differential heating. The system includes two additional terms which intensifies the vorticity and stabilizes the temperature field. These two terms bring a new complex behavior. For a large horizontal temperature difference, the onset of chaotic convection is suppressed by the temperature difference and the marginal Rayleigh number is proportional to h
2, where h is the horizontal difference in Rayleigh numbers. However, chaotic convection appears in a broad range of Rayleigh numbers.
抄録全体を表示
-
Masatoshi Yagi, Atsushi Fukuyama, Sanae–I. Itoh, Kimitaka Itoh
専門分野: Kinetic and transport theory of fluids; physical properties of gases.
1997 年 66 巻 2 号 p.
379-384
発行日: 1997/02/01
公開日: 1999/10/01
ジャーナル
認証あり
The eigenvalue equation for the current diffusive ballooning mode in tokamaks is derived taking the geometrical effects, i.e., triangularity and ellipticity into account.The stability boundary is obtained in the strong ballooning limit.It is found that the ellipticity plays an important roleon the stability of the current diffusive ballooning mode.On the other hand, the effect of the stabilization by the triangularityappears indirectly through the magnetic well term. The geometrical effect on the transport coefficient is alsodiscussed.
抄録全体を表示
-
Minoru Fukui, Yoshihiro Ishibashi
専門分野: Kinetic and transport theory of fluids; physical properties of gases.
1997 年 66 巻 2 号 p.
385-387
発行日: 1997/02/01
公開日: 1999/10/01
ジャーナル
認証あり
Traffic flow in the one-dimensional cellular automaton model including cars with the delay in restarting after a stop is simulated. With the increase of the car density, a phase transition between a free moving phase and a jam phase occurs at a critical density p
c=1/3. In the jam phase, according to the initial condition for the advance of the car, there appear the steady states where the mean velocity of the cars oscillates between two values, whose average is just (1-p)/2p.
抄録全体を表示
-
Susumu Kato, Akio Nishiguchi, Seiji Miyamoto, Kunioki Mima
専門分野: The physics of plasmas and electric discharges.
1997 年 66 巻 2 号 p.
388-391
発行日: 1997/02/01
公開日: 1999/10/01
ジャーナル
認証あり
High-order harmonic generation by an oscillating current due to intense laser electric fields in dense plasmas is investigated. In solid target plasmas produced by an intense ultra-short pulse laser, the intense laser radiation directly interacts with overdense plasmas. In such a case, plasma screening effects are important in the plasma response to the laser field. For such plasmas, the higher harmonics are evaluated by using a dynamical form factor for plasma electrons and ions. There is a peak in the harmonic spectrum at twice the plasma frequency.
抄録全体を表示
-
Huang Shi Ping, Fukuo Yoshida
専門分野: Structure of liquids and solids; crystallography.
1997 年 66 巻 2 号 p.
392-395
発行日: 1997/02/01
公開日: 1999/10/01
ジャーナル
認証あり
The molecular dynamics study is made for the metal-salt solution Ca
x(CaCl
2)
1-x. Ions are assumed to interact via an effective pair potential under a uniform background of electrons. Static structure factor and velocity autocorrelation function are calculated in the salt-rich region. Discussion is given on the concentration-dependence of the static and dynamical property.
抄録全体を表示
-
Peter Rennert, Angelika Chassé, Takeshi Nakatani, Kan Nakatsuji ...
専門分野: Surfaces and interfaces; thin films and whiskers (structure and nonelectronic properties).
1997 年 66 巻 2 号 p.
396-400
発行日: 1997/02/01
公開日: 1999/10/01
ジャーナル
認証あり
Photoelectron diffraction patterns of Si 2p core photoelectrons from Si(001) excited by photons of circular, elliptical and linear polarizations are calculated and compared with some experimental results.In accordance with the symmetry of the Si(001) sample, relations are derivedfor the total intensity, the dichroism, and the spin polarization on the azimuthal angle. These relations on one hand describe the observeddifferent peak positions in the patterns for right and left circularlypolarized radiation, and on the other hand provide information on the degree of polarization of the light.
抄録全体を表示
-
Atsushi Kamata, Kazuhiro Noguchi, Kazuhiko Suzuki, Hiroshige Tezuka, T ...
専門分野: Electron states in condensed matter.
1997 年 66 巻 2 号 p.
401-407
発行日: 1997/02/01
公開日: 1999/10/01
ジャーナル
認証あり
Resonant 2p → 3d photoemission (RPE) spectra in the valence band region of the transition-metal thiophosphates MPS
3 (M=Mn, Fe, Ni) have been measured by using synchrotron radiation. These spectra show largely enhanced resonated profiles and spread over in the wide range (--15 eV) at the incident photon energy of the transition-metal 2p
3/2 absorption peak. Comparing the obtained spectra with the result of the cluster calculation of RPE spectra for transition-metal monoxides carried out by Tanaka and Jo, we argued the differences of the two parameters, charge transfer energy Δ and d-d Coulomb interaction energy U
dd of these materials. It is suggested that MnPS
3 and FePS
3 are Mott-Hubbard type insulator with Δ > U
dd, while NiPS
3 is a charge transfer type insulator with Δ < U
dd.
抄録全体を表示
-
Satoru Inagaki
専門分野: Electron states in condensed matter.
1997 年 66 巻 2 号 p.
408-412
発行日: 1997/02/01
公開日: 1999/10/01
ジャーナル
認証あり
We solve analytically the scaling equations in the half-filled Hubbard model on the two-dimensional square lattice. The equations are coupled differential equations for the vertex functions, which were derived independently by Schulz and Dzyaloshinskii to take the electron-correlation effects into account beyond the random phase approximation. Our analytical solution confirms the results so far obtained on the scaling equations.
抄録全体を表示
-
Junichi Wakabayashi, Katsuhiko Sumiyoshi, Toshio Nagashima, Takashi Mo ...
専門分野: Electronic transport in condensed matter.
1997 年 66 巻 2 号 p.
413-418
発行日: 1997/02/01
公開日: 1999/10/01
ジャーナル
認証あり
The temperature and the current dependence of the Hall resistance in a transition region between the adjacent quantum Hall plateaus has been measured in a distributed magnetic field. We used a single crystal platelet of Bi
2Sr
2CaCu
2O
8+δ high temperature superconductor to make a distributed magnetic field. We have found a shift of the transition region between the adjacent quantum Hall plateaus to higher magnetic fields when the temperature or the current was increased. These experimental results reveal that the current distribution is concentrated near the sample edge at low temperature (current) and spreads out to the bulk region as the temperature (current) is increased. Results of calculation assuming appropriate current and magnetic field distribution have reproduced the temperature and the current dependence of the shift of the transition region.
抄録全体を表示
-
Yositake Takane, Yasusi Koyama
専門分野: Electronic transport in condensed matter.
1997 年 66 巻 2 号 p.
419-424
発行日: 1997/02/01
公開日: 1999/10/01
ジャーナル
認証あり
Andreev reflection in a one-dimensional interacting electron gas coupled with a bulk superconductor is studied theoretically. In the case of weak interaction we calculate the renormalized Andreev-reflection amplitude using a poor man's renormalization group approach, taking account of both the forward and backward scatterings due to the electron-electron interaction. The conductance as a function of temperature is obtained for arbitrary strength of the barrier potential at the normal-superconductor interface. We show that the resulting temperature dependence is stronger than that of single-barrier conductance in the one-dimensional interacting electron gas. It is also shown that any logarithmic temperature dependence does not appear in the Andreev conductance despite the presence of the backward scattering.
抄録全体を表示
-
Ryuichi Ugajin
専門分野: Electronic structure and electrical properties of surfaces, interfaces and thin films.
1997 年 66 巻 2 号 p.
425-429
発行日: 1997/02/01
公開日: 1999/10/01
ジャーナル
認証あり
Electronic states in a Hubbard chain under an overall confining potential, where electron tunneling through a Hubbard gap is seen, are investigated by the Lanczos method.The numerical results suggest that off-resonance between the ends of the chainreduces tunneling amplitude through a Hubbard gap in the centerof the chain, when the confining potential is asymmetric.This asymmetry can induce electron tunneling through a Hubbard gapeven in a chain with an odd number of electrons.
抄録全体を表示
-
Yasusi Koyama, Yositake Takane, Hiromichi Ebisawa
専門分野: Superconductivity.
1997 年 66 巻 2 号 p.
430-441
発行日: 1997/02/01
公開日: 1999/10/01
ジャーナル
認証あり
We present theoretical studies on mesoscopicfluctuations of the dc Josephson current insuper\-conductor (S)-dirty normal conductor (N)-superconductor junctions.The analytical expression for the Josephson-currentfluctuation δ J
2 is obtained byusing the thermal Green's function method, which is shown to be valid when the separationbetween two superconductors is much lager thanthe coherence length of the dirty superconductor.The effects of temperature and inelasticscattering on δ J
2 are examined.The results show that the characteristic temperature (size)for the reduction of δ J
2 is of the order ofthe Thouless correlation energy E
c(the phase choherence length).From the current correlation function, the energy correlation range is estimated to be at about E
c.In order to prepare a specific referencefor the system under our consideration, we numerically examine the critical-current fluctuationsδ J
2c in the long-junction limit in a model system.Numerical results show that the magnitude ofδ J
2c and energy correlation rangeagree with our analytical result.The effect of the barrier potential at theNS interfaces is numerically investigated.We find that the experimental result by Takayanagi et al.can be explained quantitatively within the framework of our theory.
抄録全体を表示
-
J. D. Lee, B. I. Min
専門分野: Magnetic properties and materials.
1997 年 66 巻 2 号 p.
442-450
発行日: 1997/02/01
公開日: 1999/10/01
ジャーナル
認証あり
We have analyzed the anomalous line shapes of the two-magnonRaman spectra of undoped high T
c cuprates, using the spin wave theory in a two-dimensional Heisenberg antiferromagnet.In order to describe a shoulder peak structure near 4J, which isprimarily associated with magnetic excitations of B
1g symmetry, we have explored the phonon contribution to the Raman spectra.Incorporating the magnon-phonon Hamiltonian due tothe modulated exchange interaction by phonons, we have evaluated the two-magnon Raman spectral function coming fromthe lowest order magnon-phonon-magnon scattering.It is found that the magnon-phonon-magnon scattering gives rise to a phonon-induced shoulder peak near 4J besides the dominant two-magnon peak near 3J, in good agreement with experiments.
抄録全体を表示
-
Eiji Kita, Shinichiro Kondo, Hiromitsu Ino, Michihiro Furusaka, Kiiti ...
専門分野: Magnetic properties and materials.
1997 年 66 巻 2 号 p.
451-454
発行日: 1997/02/01
公開日: 1999/10/01
ジャーナル
認証あり
Small angle scattering of neutrons and x-rays were measured in a range of0.008 ≤ q [ =(4π /λ )sin {θ] ≤ 0.2 Å
-1 for rapidly quenched La-Fe alloys. As-quenched alloysare superparamagnetic at room temperature and ferromagnetic below about270 K. Both neutron and x-ray scattering show decreases of the intensityproportional to q
-3 for the as-quenched specimen. Little effect wasobserved on decreasing the temperature to 10 K or with the application of anexternal magnetic field up to 5 kOe. These facts indicate that thescattering is not of magnetic origin. After an annealing at 350°C for 30 min., the alloys change into antiferromagnets. After heattreatment, the scattering intensity decreased considerably and its q-dependencechanged to q
-4. These results are discussed based on a two-stagesolidification process of the alloy, estimated from magnetic measurements, and the “density variation between random boundaries” model caused bynonmagnetic Fe atoms dissolved at the periphery of La grains.
抄録全体を表示
-
Shinichi Itoh, Hidekazu Tanaka, Toshiya Otomo
専門分野: Magnetic properties and materials.
1997 年 66 巻 2 号 p.
455-459
発行日: 1997/02/01
公開日: 1999/10/01
ジャーナル
認証あり
The magnetic excitations in the chain direction of an S=2 Heisenberg antiferromagnetic chain, CsCrCl
3, were measured at 20, 50, 80 and 120, K above the three-dimensional ordering temperature (T
N=16, K) by inelastic neutron-scattering experiments. The dynamical scattering function at the temperatures used in the present study was found to be well described by a classical one-dimensional Heisenberg model.
抄録全体を表示
-
Takayuki Asano, Yoshitami Ajiro, Mamoru Mekata, Kenji Kamishima, Katsu ...
専門分野: Magnetic properties and materials.
1997 年 66 巻 2 号 p.
460-465
発行日: 1997/02/01
公開日: 1999/10/01
ジャーナル
認証あり
We have confirmed from susceptibility and magnetization measurements that the Haldane state really exists in 1D phase of CsNiCl
3 which undergoes 3D ordering at T
N=4.8, K. The observed susceptibility at low fields follows the predicted curve for the S=1 quantum chain with energy gap (Δ/k
B-- 10, K) down to near T
N. A more definite evidence for the Haldane state is given by studying the effect of the nonmagnetic impurities. We have revealed a real existence of S=1/2 edge states characteristic of the Haldane state and further revealed a crossover from the quantum to classical regimes as a function of both temperature and field. The result is consistent with the model that at low temperatures (T
G=Δ/kB) and low fields (HG=Δ/gμ B) the Haldane state is well defined to form the Valence-Bond-Solid while at high temperatures (T>|J|/kB) and high fields (H>HG) the system is not in the Haldane state any more.
抄録全体を表示
-
Yasuhiro Kamada, Masaaki Matsui, Toshio Asada
専門分野: Magnetic properties and materials.
1997 年 66 巻 2 号 p.
466-471
発行日: 1997/02/01
公開日: 1999/10/01
ジャーナル
認証あり
Ni/bcc-Fe(001) multilayers have been grown by means of MBE. RHEED and X-ray diffraction patterns indicate that the structure of 3ML Ni on bcc-Fe(001) is “bct”, instead of an expected bcc structure. The magnetic moment of bct-Ni is evaluated as 0.8 μ
B at 4.5 K, where we assume that the moment of Fe is equivalent to that of bulk Fe. The band calculation of the multilayer indicates that the observed enhancement is due to the enhanced moments of Ni and Fe at the interface.
抄録全体を表示
-
Shin Nakamura, Ling Li, Midori Tanaka, Sakae Todo, Kiiti Siratori
専門分野: Magnetics resonances and relaxations in condensed matter; MÖssbauer effect.
1997 年 66 巻 2 号 p.
472-477
発行日: 1997/02/01
公開日: 1999/10/01
ジャーナル
認証あり
Mössbauer parameters of the high temperature phase of Fe
3O
4 have been precisely determined as functions of temperature. The measurements were carried out by using a stoichiometric single crystal in applied magnetic field up to 15, kOe. The values of isotropic hyperfine fields and isomer shifts at room temperature for A- and B-sites agree with those of typical 3+ and 2.5+ Fe ions, respectively, while the values of e
2qQ/2 and magnetic dipole field for B-site are too small for purely ionic state. The difference between the isomer shifts of A- and B-sites, however, becomes small above around 500--600, K. This corresponds to the contribution of A-site Fe to the electrical conduction above this temperature range. Both the absorption line width and e
2qQ/2 value of the B-site spectrum increase noticeably below around 300, K. This is noticed for the first time by our precise measurements. We consider that this feature indicate the change of the electronic states, or the formation of large polarons.
抄録全体を表示
-
Toru Ozaki, Toshirou Amau, Hiroshi Kawata, Kaoru Mizuno, Koichi Mori
専門分野: Dielectric properties and materials.
1997 年 66 巻 2 号 p.
478-484
発行日: 1997/02/01
公開日: 1999/10/01
ジャーナル
認証あり
We have carried out an X-ray intensity measurement and X-ray topography on electroded b plates of ferroelectric cesium dihydrogen phosphate, CsH
2PO
4 (CDP), using a synchrotron radiation with a wavelength of 2.482, Å above the Cs L
3-absorption edge. We have found that integrated intensities I(150) and I(\macr{1}\macr{5}0) show an anomalously large breakdown of Friedel's law, I(150)/I(\marc{1}\macr{5}0)=10.4 at 125, K, and display a ferroelectric hysteresis loop. The hysteresis loop determines that spontaneous polarization is antiparallel to the b axes set in both ferroelectric crystal structures related by inversions. The (150) diffraction topography shows that a single domain turns into a lamellar domain structure without fractal aspects after short-circuiting the b plate. The atomic displacement associated with polarization reversal is shown in a crystal structure model of 180° domains observed in the X-ray topograph.
抄録全体を表示
-
Takeo Jo, Arata Tanaka
専門分野: Optical properties and condensedmatter spectroscopy and other interactions of matter with particles and radiation.
1997 年 66 巻 2 号 p.
485-492
発行日: 1997/02/01
公開日: 1999/10/01
ジャーナル
認証あり
The difference in 4f photoemission (PES), 4f-3d X-ray emission (XES) and 4f inverse photo\-emission spectra (IPES) between the 3d core on- and off-resonances in rare earths are discussed systematically on the basis of an atomic model taking into account the full multiplet. For PES and XES, the resonant process passing through the higher-energy intermediate state of each of 3d
5/2 and 3d
3/2 absorption thresholds is shown to produce the spectral intensity corresponding to the higher-energy multiplets not accessible in the off-resonance. For IPES in rare earths with less-than-half filled 4f shells, on the other hand, the resonant process passing through the lower-energy intermediate state of each of 3d
5/2 and 3d
3/2 thresholds is shown to suppress the intensity corresponding to higher-energy multiplets seen in the off-resonance. For the higher-energy intermediate state, the IPES intensity corresponding to even higher-energy multiplets is shown to become stronger. A systematic interpretation of these selection rules in terms of the 3d-4f exchange interaction, the 3d core spin-orbit interaction and the distribution of 4f electrons in the initial state is attempted.
抄録全体を表示
-
Kaizo Nakamura, Osamu Arimoto, Masaru Eguchi, Mitsuo Nishikawa
専門分野: Optical properties and condensedmatter spectroscopy and other interactions of matter with particles and radiation.
1997 年 66 巻 2 号 p.
493-498
発行日: 1997/02/01
公開日: 1999/10/01
ジャーナル
認証あり
Luminescence spectra of tetragonal ZnP
2 crystal are measured at various temperatures. Below the indirect exciton threshold, about 30 intrinsic indirect exciton luminescence bands are confirmed. Amidst the broad bound exciton luminescence band, several emission bands appear even at 2 K. Intensities of these bands increase with increasing temperature, especially in the high energy part of the band. They are also intrinsic exciton luminescence caused through the indirect exciton transition processes accompanied by two phonons at k_1 and k_2 conserving the exciton wavevector; k
ex = k_1 + k_2.Energy difference between the lowest edges of one- and two-phonon luminescence bands 59.4 meV is equal to the largest Raman shift energy. Phonons participating in the luminescence are mainly momentum conserving phonons appearing in the one-phonon luminescence bands and the ones at the Γ point of the Brillouin zone.
抄録全体を表示
-
Minoru Horibe, Kazuyasu Shigemoto
専門分野: Statistical physics and thermodynamics.
1997 年 66 巻 2 号 p.
499-500
発行日: 1997/02/01
公開日: 1999/10/01
ジャーナル
認証あり
-
Ichiro Hiromitsu, Nobuhisa Ikeda, Takashi Ito
専門分野: Structure of liquids and solids; crystallography.
1997 年 66 巻 2 号 p.
501-502
発行日: 1997/02/01
公開日: 1999/10/01
ジャーナル
認証あり
-
Chikara Sugiura, Hiroharu Yorikawa, Shinji Muramatsu
専門分野: Electron states in condensed matter.
1997 年 66 巻 2 号 p.
503-504
発行日: 1997/02/01
公開日: 1999/10/01
ジャーナル
認証あり
-
Ryosuke Kadono
専門分野: Magnetic properties and materials.
1997 年 66 巻 2 号 p.
505-506
発行日: 1997/02/01
公開日: 1999/10/01
ジャーナル
認証あり
