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Volume 73, Issue 1
Displaying 1-45 of 45 articles from this issue
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Naokazu Shibata, Daijiro Yoshioka2004 Volume 73 Issue 1 Pages 1-4
Published: January 15, 2004
Released on J-STAGE: July 25, 2007
JOURNAL RESTRICTED ACCESSThe stripe state in the lowest Landau level is studied by the density matrix renormalization group (DMRG) method. The ground state energy and pair correlation functions are systematically calculated at various pseudopotentials in the lowest Landau level. We show that the stripe state in the lowest Landau level is realized only in a system whose width perpendicular to the two-dimensional electron layer is smaller than the order of magnetic length.View full abstractDownload PDF (138K) -
Y. Nakajima, K. Izawa, Y. Matsuda, S. Uji, T. Terashima, H. Shishido, ...2004 Volume 73 Issue 1 Pages 5-8
Published: January 15, 2004
Released on J-STAGE: July 25, 2007
JOURNAL RESTRICTED ACCESSThe normal-state Hall effect and magnetoresisitance (MR) have been measured in the quasi two dimensional (2D) heavy fermion superconductor CeCoIn5. In the non-Fermi liquid region where the reistivity ρxx exhibits an almost perfect T-linear dependence, the Hall angle varies as cotθH∝T2 and MR displays a strong violation of Kohler’s rule. We demonstrate a novel relation between the MR and the Hall conductivity, Δρxx⁄ρxx∝(σxyρxx)2. These results bear a striking resemblance to the normal-state properties of high-Tc cuprates, indicating universal transport properties in the presence of quasi-2D antiferromagnetic fluctuations near a quantum critical point.View full abstractDownload PDF (108K) -
Yositake Takane2004 Volume 73 Issue 1 Pages 9-12
Published: January 15, 2004
Released on J-STAGE: July 25, 2007
JOURNAL RESTRICTED ACCESSThe Dorokhov–Mello–Pereyra–Kumar (DMPK) equation for transmission eigenvalues is derived for metallic carbon nanotubes with several conducting channels when the potential range of scatterers is larger than the lattice constant. With increasing system length L, the system approaches a fixed point, where only one channel is perfectly conducting and other channels are completely closed. The asymptotic behavior of the conductance in the long-L regime is investigated on the basis of the DMPK equation. It is shown that the length scale for the exponential decay of the typical conductance is reduced due to the presence of the perfectly conducting channel. If a magnetic field is applied, the system falls into the unitary class. It is pointed out that this transition is characterized by the disappearance of the perfectly conducting channel and the increase in decay length for the typical conductance.View full abstractDownload PDF (92K) -
Tadashi Fukuhara, Hiroko Matsuda, Shinichi Masubuchi, Kiyoshi Ooiwa, Y ...2004 Volume 73 Issue 1 Pages 13-16
Published: January 15, 2004
Released on J-STAGE: July 25, 2007
JOURNAL RESTRICTED ACCESSWe have investigated the field dependence of the Hall resistivity for Fe2+xV1−xAl (x=0, 0.1, 0.2) and Fe2+xV1−xGa (x=−0.1, 0.0, 0.1). The carrier concentration of nonmetallic Fe2VAl is expected to be of the order of 1% of ordinary metals. The extraordinary Hall effect in the ferromagnetically ordered state is mainly characterized by the side-jump effect occurring in ferromagnetic clusters that have a metallic nature.View full abstractDownload PDF (366K) -
Hiroaki Ikeda, Yunori Nisikawa, Kosaku Yamada2004 Volume 73 Issue 1 Pages 17-20
Published: January 15, 2004
Released on J-STAGE: July 25, 2007
JOURNAL RESTRICTED ACCESSStimulated by the recent finding of the superconductivity in Na0.35CoO2.1.3H2O, we investigate superconducting instabilities on a 2D triangular lattice in the repulsive Hubbard model. Using the third-order perturbation expansion with respect to the on-site repulsion U, we evaluate the linearized Dyson–Gor’kov equation. We find that f-wave spin-triplet pairing is the most stable in a wide range of the next-nearest-neighbor hopping integral t′ and electron number density n. The introduction of t′ is crucial for adjusting the van Hove singularities to the neighborhood of the Fermi surface crossing around the K point. In this case, the bare spin susceptibility shows a broad peak around the Γ point. These conditions stabilize f-wave pairing. Although f-wave pairing is also given by the fluctuation-exchange approximation, the transition temperature is too low to be observed. This is because the depairing effect by the spin fluctuation is overestimated. Thus, the third-order vertex corrections are important for the spin-triplet superconductivity, similar to the case of Sr2RuO4.View full abstractDownload PDF (303K) -
Takafumi Kita2004 Volume 73 Issue 1 Pages 21-24
Published: January 15, 2004
Released on J-STAGE: July 25, 2007
JOURNAL RESTRICTED ACCESSThis paper presents a microscopic calculation of the flux-flow resistivity ρf for s-wave type-II superconductors with arbitrary impurity concentrations near the upper critical field Hc2. It is found that, as the mean free path l becomes longer, ρf increases gradually from the dirty-limit result of Thompson [Phys. Rev. B 1 (1970) 327] and Takayama and Ebisawa [Prog. Theor. Phys. 44 (1970) 1450]. The limiting behaviors suggest that ρf(H) at low temperatures may change from convex downward to upward as l increases, thus deviating substantially from the linear dependence ρf∝H⁄Hc2 predicted by the Bardeen–Stephen theory [Phys. Rev. 140 (1965) A1197].View full abstractDownload PDF (133K) -
Hiori Kino, Hiroshi Kontani, Tsuyoshi Miyazaki2004 Volume 73 Issue 1 Pages 25-28
Published: January 15, 2004
Released on J-STAGE: July 25, 2007
JOURNAL RESTRICTED ACCESSWe present a theoretical study on the superconductivity of β′-(BEDT-TTF)2ICl2 at Tc=14.2 K under a high hydrostatic pressure recently found, which is the highest among organic superconductors. In the present work, we study an effective model using the fluctuation-exchange (FLEX) approximation based on the results of first-principles calculation. In the obtained phase diagram, the superconductivity with dxy-like symmetry is realized next to the antiferromagnetic phase, as a result of the one-dimensional to two-dimensional crossover driven by the pressure.View full abstractDownload PDF (123K) -
Yasuhiro Yoshino, Shinichiro Kobayashi, Shigenari Tsuji, Hideki Tou, M ...2004 Volume 73 Issue 1 Pages 29-32
Published: January 15, 2004
Released on J-STAGE: July 25, 2007
JOURNAL RESTRICTED ACCESSThe Nd ion doping effects on the multipolar interactions in CeB6 were studied. At high magnetic fields, the antiferro-quadrupolar (AFQ) phase II is not significantly affected by Nd doping. This may be because the Nd ion is in the paramagnetic state. However, with decreasing magnetic field, the Nd doping effect becomes apparent. This may be because Nd–Nd interaction dominates the long-range ordering at low magnetic fields. At low magnetic fields, just after TQ and TN coincide with each other when Nd ion is doped, new phases, namely, phases IIIA and V appear. Phase IIIA is the AF magnetic state where all types of quadrupolar interaction are small. The nature of phase V seems to change largely at x∼0.5. For x<0.4, phase V may be the same as the type I AF magnetic state observed in NdB6 where the O20-type FQ interaction is prominent. In phase V for x>0.5, the AF magnetic state where both Ce and Nd ions contribute may be realized.View full abstractDownload PDF (102K) -
Yukio Saito, Hiroyuki Hyuga2004 Volume 73 Issue 1 Pages 33-35
Published: January 15, 2004
Released on J-STAGE: July 25, 2007
JOURNAL RESTRICTED ACCESSThe nonlinear autocatalysis of the chiral substance is shown to achieve homochirality in a closed system, if the back reaction is included. Asymmetry in the concentration of two enantiomers or enantiometric excess increases due to the nonlinear autocatalysis. Furthermore, when the back reaction is taken into account, the reactant supplied by the decomposition of the enantiomers is recycled to produce more of the dominant enantiomer, and eventually homochirality is established.View full abstractDownload PDF (105K) -
Chenglin Bai2004 Volume 73 Issue 1 Pages 37-41
Published: January 15, 2004
Released on J-STAGE: July 25, 2007
JOURNAL RESTRICTED ACCESSBy means of extended homogeneous balance method and variable separation approach, quite a general excitation of the (2+1)-dimensional Broer–Kaup (BK) equations is derived. Some types of the usual localized excitations such as dromions, lumps, rings, and oscillating soliton excitations can be easily constructed by selecting the arbitrary functions appropriately. Besides these usual localized structures, some new localized excitations like fractal-dromion, fractal-lump, and multi-peakon excitations of this BK system are found by selecting appropriate functions.View full abstractDownload PDF (353K) -
A. H. Khater, W. Malfliet, D. K. Callebaut, S. F. Abdul-Aziz2004 Volume 73 Issue 1 Pages 42-48
Published: January 15, 2004
Released on J-STAGE: July 25, 2007
JOURNAL RESTRICTED ACCESSThe invariance under continuous group of transformations of the nonlinear diffusion equation in an inhomogeneous medium f(x)ut=(g(x)unux)x with arbitrary thermal coefficients f(x) and g(x) is studied. The infinitesimals, similarity variables, dependent variables, and reduction to quadrature or exact solutions of this equation for physically realizable forms of f(x), g(x) and n are obtained too. Some interesting results of this study are new exact solutions, that do not seem to have been reported in the literature.View full abstractDownload PDF (115K) -
Kyungsik Kim, Seong-Min Yoon2004 Volume 73 Issue 1 Pages 49-52
Published: January 15, 2004
Released on J-STAGE: July 25, 2007
JOURNAL RESTRICTED ACCESSWe study the tick dynamical behavior of the bond futures price using the rescaled range analysis (R/S analysis) in Korean futures exchange market. For our case, the multifractal Hurst exponents with long-run memory effects can be obtained from two kinds of Korean treasury bond futures transacted recently. It exists no crossover for the Hurst exponents at charateristic time scales. Particularly, we find that our result for probability distribution of prices is similar to a Lorentz distribution different from fat-tailed properties of bond futures price.View full abstractDownload PDF (146K) -
Yu Itoh, Kei-ichi Tainaka2004 Volume 73 Issue 1 Pages 53-59
Published: January 15, 2004
Released on J-STAGE: July 25, 2007
JOURNAL RESTRICTED ACCESSThe extinction process in model ecosystems is studied on two-dimensional lattice. Simulations are carried out by two different methods: lattice model (LM) and mean-field simulation (MFS). In the former case interaction occurs between adjacent lattice points, whereas in the latter case interaction globally occurs between any pair of lattice points. Computer simulation reveals the occurrence of fluctuation enhancement which means that there are a variety of paths to the extinction. It is found that the enhancement for LM is stronger, compared to MFS. The critical behavior of extinct species may play an important role for the enhancement.View full abstractDownload PDF (231K) -
Nobuya Maeshima2004 Volume 73 Issue 1 Pages 60-67
Published: January 15, 2004
Released on J-STAGE: July 25, 2007
JOURNAL RESTRICTED ACCESSVertical density matrix algorithm (VDMA), a tensor product state formulation of the “higher-dimensional” density matrix renormalization group, is applied to the spin 1/2 antiferromagnetic XXZ model on the checkerboard lattice. The VDMA was, in the preceding study, applied to the transverse field Ising model on the square lattice and the three-dimensional classical Ising model. In the present paper, its implementation procedure is modified in order to apply the VDMA to the XXZ model. Numerical accuracy of the VDMA is investigated for the XXZ model on the square lattice, which shows that the method gives reliable results for the ground state energy. In the frustrated region, VDMA results are compared with a simple calculation based on a magnetically disordered state. It is found that the weakly frustrated region is in the Néel ordered phase, while in the strongly frustrated region the realized phase cannot be identified clearly by the obtained results.View full abstractDownload PDF (569K) -
Ryo Kawahara, Hiizu Nakanishi2004 Volume 73 Issue 1 Pages 68-75
Published: January 15, 2004
Released on J-STAGE: July 25, 2007
JOURNAL RESTRICTED ACCESSThe free cooling process in the inelastic hard sphere system is studied by analysing the data from large scale molecular dynamics simulations on a three dimensional system. The initial energy decay, the velocity distribution function, and the velocity correlation functions are calculated to be compared with theoretical predictions. The energy decay rate in the homogeneous cooling state is slightly but distinctively smaller than that expected from the independent collision assumption. The form of the one particle velocity distribution is found not to be stationary. These contradict to the predictions of the kinetic theory based on the Enskog–Boltzmann equation and suggest that the velocity correlation is already important in the early stage of homogeneous cooling state. The energy decay rate is analysed in terms of the velocity correlation.View full abstractDownload PDF (249K) -
Tiberiu Tudor2004 Volume 73 Issue 1 Pages 76-85
Published: January 15, 2004
Released on J-STAGE: July 25, 2007
JOURNAL RESTRICTED ACCESSAn analysis of the generalized coherence of multifrequency optical fields is given, both in terms of observable quantities (coherence functions) and in terms of field quantities (analytical signal and amplitude spectral density of the field). The spectral structure of the generalized coherence function for a widespread class of multifrequency optical fields is given. Experimental results obtained by interferometrical investigation of the generalized coherence of such fields are presented.View full abstractDownload PDF (181K) -
Takao Yoshinaga, Takuya Yoshida2004 Volume 73 Issue 1 Pages 86-93
Published: January 15, 2004
Released on J-STAGE: July 25, 2007
JOURNAL RESTRICTED ACCESSWe investigate long wave instability of the bulge mode on a free liquid sheet subject to a temperature difference between both surfaces. Considering the temperature dependence of the surface tension and viscosity, we derive linear evolution equations for the bulge mode under the membrane approximation. The temporal and spatial instabilities of the mode are mainly examined for the temperature difference |ΔΘ|. It is shown that there exist two critical temperature differences ΔΘc and ΔΘs. For |ΔΘ|>ΔΘc, the sheet becomes unstable for both instabilities, where the sheet remains stationary for the temporal instability, while oscillatory for the spatial instability. On the other hand, when |ΔΘ| varies across ΔΘs, the sheet becomes oscillatory from stationary but remains stable for the temporal instability. Furthermore, it is shown for both instabilities that the increase of the temperature dependence of viscosity stabilizes the sheet.View full abstractDownload PDF (194K) -
Junji Nakahara, Takahiro Miyoshi, Kanya Kusano2004 Volume 73 Issue 1 Pages 94-101
Published: January 15, 2004
Released on J-STAGE: July 25, 2007
JOURNAL RESTRICTED ACCESSThree dimensional local simulation was performed to investigate the energy conversion and the dynamo action in the magnetohydrodynamic (MHD) turbulence due to the magnetorotational instability (MRI) in a differentially rotating disk, using Arbitrary Lagrangian Eulerian method. As a result, it was found that the turbulence plays a role to convert the magnetic energy to the kinetic energy, if the shear parameter q defined by −dlnΩ⁄dlnR is less than 2.3, where Ω and R are the angular velocity and the disk radius, respectively. It means that amplification of the magnetic energy in the MRI is mainly due to the twisting effect of differential rotation rather than a result of the turbulent dynamo action. When q≥2.5, the energy conversion rate from the kinetic energy to the magnetic energy is switched to positive, because low modes, which are destabilized by the Rayleigh instability, can work for the turbulent dynamo. On the other hand, it is also revealed that, the α-dynamo effect exists at least for q≥0.75, although the contribution to the amplification of the magnetic energy is very small. From these results, it can be concluded that, even though the MRI is able to amplify the magnetic energy, the turbulence due to the MRI is less effective as a driver of the conventional dynamo process, unless the Rayleigh instability arises.View full abstractDownload PDF (428K) -
Yasuhito Kiwamoto, Akihiro Mohri, Masami Fujiwara2004 Volume 73 Issue 1 Pages 102-106
Published: January 15, 2004
Released on J-STAGE: July 25, 2007
JOURNAL RESTRICTED ACCESSThe equilibrium density distribution of a nonneutral plasma consisting of two species of particles is studied theoretically on a basis of a cold two-fluid model. We request an equilibrium state with rigid rotation and seek the distribution with minimum energy satisfying the conservation of the particle numbers and the canonical angular momentum. The analysis indicates that the overlapping of the distributions of the fluids is allowed only while the total density is below the Brillouin density limit of the heavier fluid. With increasing number of the lighter particles the heavier fluid is pushed out and surrounds the lighter fluid with increasing radial separation. The rotation of the heavier fluid changes from the low frequency branch to the upper branch as the density of lighter particles further increases. When the number of the heavier particles rotating in the low branch is increased, the inner edge of the heavier fluid shrinks to compress the lighter fluid, but when the rotation is switched to the upper branch the outer edge of the lighter fluid expands.View full abstractDownload PDF (134K) -
Mitsuo Machida, Hiroyuki Uchida, Toku Ishibashi, Hiroki Taniguchi, Mas ...2004 Volume 73 Issue 1 Pages 107-115
Published: January 15, 2004
Released on J-STAGE: July 25, 2007
JOURNAL RESTRICTED ACCESSCrystal structure of deuterated glycinium phosphite was studied in the paraelectric (P) phase at 348 K and in the ferroelectric (F) phase at 223 K by means of the single crystal neutron diffraction. Deuteration rate is estimated to be 0.939 by the least-squares refinement. In the P phase, quasi-one-dimensional hydrogen bond chains are built by mutually linking the DPO32− anions through two different types of hydrogen bonds with the bond angles of 179.2 and 171.6°. Two independent deuterons within the hydrogen bonds forming the chains are disordered over two sites separated by 0.545 and 0.539 Å. In the F phase, they order at a position nearly equal to one of two sites related by the disorder in the P phase. With the ordering of the deuterons, the P–O bonds with covalently bonded deuteron elongate, and those without covalently bonded deuteron reduce their lengths to some extent from the values determined in the P phase. Two oxygens involved in the hydrogen bond with the bond angle 179.2° exhibits especially large displacements in the F phase. This suggests strongly an importance of this hydrogen bond in the polarization appearance and in the ferroelectric transition. Comparison with results of non-deuterated salt indicates that only the hydrogen bonds forming the chains show significant isotope shift. In particular, the hydrogen bond with the bond angle 179.2° exhibits the most pronounced shift on the angle parameter defined by the angle between the line connecting two sites of disordered proton or deuteron and the line connecting two oxygens involved in the hydrogen bond.View full abstractDownload PDF (353K) -
Masashi Watanabe, Yukio Noda, Yoshio Nogami, Hatsumi Mori2004 Volume 73 Issue 1 Pages 116-122
Published: January 15, 2004
Released on J-STAGE: July 25, 2007
JOURNAL RESTRICTED ACCESSθ-(BEDT-TTF)2RbZn(SCN)4 is a two-dimensional organic conductor exhibiting a metal–insulator transition at TMI=200 K. This insulating charge ordered state below TMI was investigated by a single crystal structural analysis taking account of the superlattice formation below TMI. A large displacement (about 0.2 Å) of BEDT-TTF molecules associated with the transition was found. Transfer integrals between BEDT-TTF molecules were also calculated from the structural data. The two-dimensional net of transfer integrals above TMI was modulated into the quasi one-dimensional transfer integral chain by the superlattice formation below TMI. The ionicities of BEDT-TTF molecules are estimated from the intramolecular bond length distribution. As a result, charge disproportionation between BEDT-TTF molecules was found, and the ionicity was 0 to +0.2 and +0.8 to +1.0 respectively. The hole-rich sites are laid on the quasi one-dimensional transfer integral chain. We conclude that the spatial pattern of charge ordering is a stripe alternating along the c-axis.View full abstractDownload PDF (371K) -
D. L. Wang, X. H. Yan, Y. Tang2004 Volume 73 Issue 1 Pages 123-129
Published: January 15, 2004
Released on J-STAGE: July 25, 2007
JOURNAL RESTRICTED ACCESSBy using the quasidiscrete multiple-scale method, we study the nonlinear properties of a monoatomic chain with Kac–Baker-like long-range harmonic interaction. Besides the usual asymmetric envelope solitons, a novel nonliear elementary excitation, a hole-soliton, is analytically derived. It is found that the dispersion relation and group velocity exhibit some characters different from that of the nonlinear chain without Kac–Baker-like long-range harmonic interaction. Furthermore, these solitons are nonpropagating at other sites except for the center of Brillouin zone, and the group velocity of the soliton at the center of Brillouin zone is supersonic.View full abstractDownload PDF (311K) -
Tadao Ishii, Atsushi Ichigozaki2004 Volume 73 Issue 1 Pages 130-135
Published: January 15, 2004
Released on J-STAGE: July 25, 2007
JOURNAL RESTRICTED ACCESSThe relaxations by proton hopping in a perovskite lattice are theoretically investigated: the 24 sites available for protons in the primitive unit cell give rise to the 24 relaxation branches composed of 1 diffusive (ε=1) and 23 nondiffusive bands (ε=2–24). It turns out that two lowest nondiffusive modes ε=2,3, being degenerate at q=0, can work for a radio-frequency dielectric function. On the other hand, the cell including a dopant results in impurity modes when proton has a deep potential energy as a trapping state. The impurity modes consist of five radio frequency modes, two- and three-degenerate modes. It is discussed how these relaxation modes and impurity modes get involved in proton diffusions or two-peaks mechanism of the dielectric loss, experimentally observed.View full abstractDownload PDF (211K) -
Junichiro Koga, Kengo Nishio, Toshio Yamaguchi, Fumiko Yonezawa2004 Volume 73 Issue 1 Pages 136-144
Published: January 15, 2004
Released on J-STAGE: July 25, 2007
JOURNAL RESTRICTED ACCESSOrder N non-orthogonal tight-binding molecular dynamics based on the Fermi operator expansion method is implemented and tested, where N is the number of atoms. The method is described in detail, with several notes on the actual implementation. We find that the potential energy and forces consistent with it are calculated in an O(N) fashion almost as easily as in the cases of orthogonal tight-binding models. Our method thus implemented is applied to the study of glass transition in germanium (Ge). We quench liquid Ge well above melting temperature by an NVT ensemble molecular dynamics simulation, with N=512. We investigate the pair correlation function, the static structure factor, and the bond-angle distribution function for liquid, super-cooled liquid, and amorphous Ge. From the analyses of these properties, we find that substantial structural changes occur when the temperature of liquid Ge is decreased. In particular, we find that with the decrease of temperature, covalent bonds in liquid Ge become more significant, and transform from a highly distorted tetrahedral-like bonding to a diamond-like tetrahedral bonding.View full abstractDownload PDF (272K) -
Fumiyuki Ishii, Tamio Oguchi2004 Volume 73 Issue 1 Pages 145-151
Published: January 15, 2004
Released on J-STAGE: July 25, 2007
JOURNAL RESTRICTED ACCESSWe have performed first-principles band structure calculation for CeRhAs and its isostructural Ce compounds. Calculated insulating and metallic or semimetallic ground states are consistent with recent experimental observations. We discussed projected density of states on Ce 4f |J,JZ⟩ states, which is a clue to understand the anisotropic effects to realize the ground state and gap formation. Band gap and pseudogaps are opened mainly due to Ce 4f |5⁄2,±5⁄2⟩ states. These states are very sensitive to lattice deformation. Gap formation and structural instability in CeRhAs may be understood by orientations of Ce 4f orbitals.View full abstractDownload PDF (492K) -
Arata Tanaka2004 Volume 73 Issue 1 Pages 152-162
Published: January 15, 2004
Released on J-STAGE: July 25, 2007
JOURNAL RESTRICTED ACCESSThe metal–insulator (M–I) transitions in VO2 and Ti2O3 were investigated using the three-band Hubbard model in connection with the on-site exchange interaction and lattice distortions. Although these two compounds have different crystal structures, the mechanism of the phase transitions can be understood from a unified viewpoint; an increase in energy level separation among the t2g orbitals caused by the lattice distortion triggers an abrupt change in the electron configuration in doubly occupied sites from an S=1 Hund’s coupling state to a low-spin S=0 state with much larger energy and this strongly suppresses the charge fluctuation, resulting in localization of electrons. These M–I transitions are not induced by an increase in relative strength of the Coulomb interaction against the electron hopping as in the conventional scenario of the Mott–Hubbard transition but by the level splitting among the t2g orbitals against the on-site exchange interaction. Switching of the nearest-neighbor spin and orbital correlations and large change in the orbital occupation occur at the M–I transitions. Observation of the change in the orbital occupation at the M–I transitions by the linear dichroic V or Ti 2p x-ray absorption spectroscopy can be a crucial check to this theory.View full abstractDownload PDF (436K) -
Yoshihide Tanaka, Akira Oguri2004 Volume 73 Issue 1 Pages 163-172
Published: January 15, 2004
Released on J-STAGE: July 25, 2007
JOURNAL RESTRICTED ACCESSWe study correlation effects on the transport through a quantum dot superlattice using a two-dimensional Hubbard model connected to two noninteracting leads. To calculate the zero-temperature conductance away from half-filling, we have used the non-magnetic solution of the Hartree–Fock approximation for the unperturbed Green’s function, and then take into account the electron correlation beyond the mean field theory through the second-order self-energy corrections with respect to the residual interaction. When the value of the onsite potential εd or the repulsion U is changed, the conductance shows a number of peaks corresponding to the resonance states passing through the Fermi energy. The behavior of the resonance states for correlated electrons can be investigated using the eigenvalue of the effective Hamiltonian for a quasi-particle of a local Fermi liquid. We calculate the eigenvalue using the second-order self-energy, and show explicitly that it can be compared with the conductance peak.View full abstractDownload PDF (458K) -
Kohei M. Itoh, Michio Watanabe, Youiti Ootuka, Eugene E. Haller, Tomi ...2004 Volume 73 Issue 1 Pages 173-183
Published: January 15, 2004
Released on J-STAGE: July 25, 2007
JOURNAL RESTRICTED ACCESSWe report on the complete scaling analysis of low temperature electron transport properties with and without magnetic field in the critical regime for the metal–insulator transition in two series of homogeneously doped p-type Ge samples: i) nominally uncompensated neutron-transmutation-doped (NTD) 70Ge:Ga samples with the technological compensation ratio K<0.001, and ii) intentionally compensated NTD natGe:Ga,As samples with K=0.32. For the case of the uncompensated series in zero magnetic field, the critical exponents μ, ν, and ζ determined for the electrical conductivity (σ), localization length (ξ), and impurity dielectric susceptability (χimp), respectively, change at the very vicinity of the critical Ga concentration (N∼Nc). Namely, the anomalous critical exponents, e.g. μ≈0.5, change to μ≈1 only within the region 0.99Nc<N<1.01Nc. On the other hand, the same critical behavior, μ≈1, was found for the K=0.32 series in much larger region 0.25Nc<N<2.4Nc. This finding suggests that the μ≈1 critical behavior observed for the nominally uncompensated series in the extremely narrow region is due to the presence of the self-compensation of acceptors by native defects and/or technologically unavoidable very small amount of doping compensation (K<0.001). Therefore, the width of the concentration that can be fitted with μ≈1 around Nc is likely to scale with the degree of compensation (K), and disappears in the limit K→0, i.e., only the region with the anomalous exponent μ≈0.5 remains for the case of K=0. An externally applied magnetic field to nominally uncompensated samples also broadens the width of μ≈1 around Nc, but with a mechanism clearly different from that of compensation. The unified description of our experimental results unambiguously establishes the values of the critical exponents μ, ν, and ζ for doped semiconductors with and without compensation and magnetic field.View full abstractDownload PDF (265K) -
Naoki Yoneyama, Takahiko Sasaki, Terukazu Nishizaki, Norio Kobayashi2004 Volume 73 Issue 1 Pages 184-189
Published: January 15, 2004
Released on J-STAGE: July 25, 2007
JOURNAL RESTRICTED ACCESSWe investigate the influence of disorders in terminal ethylene groups of BEDT-TTF molecules (ethylene-disorders) on the vortex pinning of the organic superconductor κ-(BEDT-TTF)2Cu[N(CN)2]Br. Magnetization measurements are performed under different cooling-processes. The second peak in the magnetization hysteresis curve is observed for all samples studied, and the hysteresis width of the magnetization becomes narrower by cooling faster. In contradiction to the simple pinning effect of disorder, this result shows the suppression of the vortex pinning force by introducing more ethylene-disorders. The ethylene-disorder domain model is proposed for explaining the observed result. In the case of the system containing a moderate number of the ethylene-disorders, the disordered molecules form a domain structure and it works as an effective pinning site. On the contrary, an excess number of the ethylene-disorders may weaken the effect of the domain structure, which results in the less effective pinning force on the vortices.View full abstractDownload PDF (289K) -
Yutaka Kishimoto, Yu Kawasaki, Takashi Ohno, Laxmi C. Gupta, Goutam Gh ...2004 Volume 73 Issue 1 Pages 190-193
Published: January 15, 2004
Released on J-STAGE: July 25, 2007
JOURNAL RESTRICTED ACCESSTo investigate the electronic state of LaRu3Si2, we have carried out 139La-NQR measurement. In the normal state, the spin–lattice relaxation rate 1⁄T1 is proportional to the temperature T. 1⁄T1 shows a coherence peak just below the superconducting transition temperature Tc=6.5 K and decreases exponentially well below Tc. LaRu3Si2 is found to be a strong coupling BCS superconductor with a large energy gap 2Δ(0)=5.50kBTc. A relatively high Tc in LaRu3Si2 is presumably due to a high density of states of conduction electrons at Fermi surface and strong electron–phonon interaction.View full abstractDownload PDF (121K) -
Yu Kawasaki, Kenji Ishida, Shinji Kawasaki, Takeshi Mito, Guo-qing Zhe ...2004 Volume 73 Issue 1 Pages 194-197
Published: January 15, 2004
Released on J-STAGE: July 25, 2007
JOURNAL RESTRICTED ACCESSWe report a pressure (P) effect on CeCu2(Si0.98Ge0.02)2 where an antiferromagnetic (AFM) order at TN∼0.75 K coexists with superconductivity below Tc∼0.4 K. At pressures exceeding P=0.19 GPa, the AFM order is suppressed, which demonstrates that the sudden emergence of AFM order due to the Ge doping is ascribed to the intrinsic lattice expansion. The exotic superconductivity at P=0 GPa is found to evolve into a typical heavy-fermion one with a line-node gap above P=0.91 GPa. We highlight that the anomalous enhancement in nuclear spin–lattice relaxation rate 1⁄T1 that follows a T1T = const. behavior well below Tc at P=0 GPa is characterized by the persistence of low-lying magnetic excitations, which may be inherent to the coexistent state of antiferromagnetism and superconductivity.View full abstractDownload PDF (104K) -
Yoshiei Todate2004 Volume 73 Issue 1 Pages 198-205
Published: January 15, 2004
Released on J-STAGE: July 25, 2007
JOURNAL RESTRICTED ACCESSA simple model of dilute, quasi-random antiferromagnet with local atomic correlation has been presented. The simulation study for Ising spins on this quasi-random lattice has revealed some interesting magnetic properties. Spin-glass-like cusp and anomaly in the linear and nonlinear susceptibilities are observed, while the model exhibits a second-order antiferromagnetic transition. It has been found that the magnetization induced by the external field is much larger than that in the simple random dilute case. It is suggested that the characteristic magnetic properties are originated in the large amplitude of the magnetization fluctuation in the correlated lattice.View full abstractDownload PDF (1954K) -
Masatsugu Suzuki, Itsuko S. Suzuki, Tedmann M. Onyango, Toshiaki Enoki2004 Volume 73 Issue 1 Pages 206-215
Published: January 15, 2004
Released on J-STAGE: July 25, 2007
JOURNAL RESTRICTED ACCESSH–T diagram of 3D diluted Ising antiferromagnet NicMg1−c(OH)2 with c=0.8 has been determined from measurements of SQUID DC magnetization and AC magnetic susceptibility. At H=0, this compound undergoes two magnetic phase transitions: an antiferromagnetic (AF) transition at the Néel temperature TN (=20.7 K) and a reentrant spin glass (RSG) transition at TRSG (≈6 K). The H–T diagram consists of the RSG, spin glass (SG), and AF phases. These phases meet a multicritical point Pm (Hm=42 kOe, Tm=5.6 K). The irreversibility of susceptibility defined by δ (=χFC−χZFC) shows a negative local minimum for 10≤H≤35 kOe, suggesting the existence of possible glassy phase in the AF phase. A broad peak in δ and χ″ at H≥20 kOe for TN(c=0.8,H)≤T≤TN(c=1,H=0) (=26.4 K) suggests the existence of the Griffiths phase.View full abstractDownload PDF (307K) -
Katsunori Kubo, Yoshio Kuramoto2004 Volume 73 Issue 1 Pages 216-224
Published: January 15, 2004
Released on J-STAGE: July 25, 2007
JOURNAL RESTRICTED ACCESSAn octupole ordering model is studied by the mean field theory, and its relevance to the phase IV of CexLa1−xB6 is discussed. The observed lattice distortion along the [111] direction is interpreted in terms of the Γ5g-type ferro-quadrupole moment induced by an antiferro-octupole ordering with Γ5u symmetry. The octupole model also accounts for the cusp in the magnetization as in the Néel transition, and the softening of the elastic constant C44 below the ordering temperature. However, the internal magnetic field due to the octupole moment is smaller than the observed one by an order of magnitude. Also discussed is the possibility of a pressure induced antiferromagnetic moment in the octupole-ordered state.View full abstractDownload PDF (193K) -
Gen’ya Sakurai, Yoshio Kuramoto2004 Volume 73 Issue 1 Pages 225-238
Published: January 15, 2004
Released on J-STAGE: July 25, 2007
JOURNAL RESTRICTED ACCESSMicroscopic investigation is performed for intersite multipolar interactions in the orbitally degenerate Anderson lattice, with CeB6 taken as an exemplary target. In addition to the f0 intermediate state, f2 Hund’s-rule ground states are included as intermediate states for the interactions. The conduction-band states are taken as plane waves and the hybridization as spherically symmetric. The spatial dependences of multipolar interactions are given by the relative weight of partial wave components along the pair of sites. It is clarified how the the anisotropy arises in the interactions depending on the orbital degeneracy and the spatial configuration. The stability of the Γ5 antiferro-quadrupole order in the phase II of CeB6 is consistent with our model. Moreover, the pseudo-dipole interactions follow a tendency required by the phenomenological model for the phase III.View full abstractDownload PDF (279K) -
S. Takahashi, T. Ueda, L. Zhang2004 Volume 73 Issue 1 Pages 239-244
Published: January 15, 2004
Released on J-STAGE: July 25, 2007
JOURNAL RESTRICTED ACCESSThe minor hysteresis loops were measured with increasing magnetic field amplitude, Ha, step by step and analyzed in connection with the lattice defects such as dislocations in Fe single crystal. We defined pseudo coercive force Hc*, susceptibility χH* at Hc*, pseudo hysteresis loss WF*, pseudo remanence BR*, pseudo remanence work WR*, susceptibility χR* at BR*, and pseudo magnetization Ba* at Ha in the minor loop. Hc* is the magnetic field where the magnetization becomes zero in a minor loop. A simple relation, 2Hc*=Ha, was experimentally obtained in a wide Ha range. These parameters reflect simple Bloch wall potential on the supposition that Bloch walls receive force from the same potential; the potential is the average one of individual Bloch wall. The initial stage of potential is concluded to be irreversible from the magnetic pseudo properties.View full abstractDownload PDF (175K) -
Minoru Takahashi, Go Kato, Masahiro Shiroishi2004 Volume 73 Issue 1 Pages 245-253
Published: January 15, 2004
Released on J-STAGE: July 25, 2007
JOURNAL RESTRICTED ACCESSThe second neighbor correlation functions of the spin-\\frac12 XXZ chain in the ground state are expressed in the form of three dimensional integrals. We show that these integrals can be reduced to one-dimensional ones and thereby evaluate the values of the next nearest-neighbor correlation functions for Δ>1.View full abstractDownload PDF (155K) -
Takashi Shirahata, Tota Nakamura2004 Volume 73 Issue 1 Pages 254-261
Published: January 15, 2004
Released on J-STAGE: July 25, 2007
JOURNAL RESTRICTED ACCESSWe have modeled magneto–dielectric phase transitions in ABX3-type layered triangular lattice compounds. The model consists of a spin system (magnetic transition) and a lattice system (dielectric transition). Magnetic exchange interactions are supposed to change with a relative position between two spins. This assumption produces an effective coupling between the lattice and the spin. Applying the nonequilibrium relaxation method, we have found that a simultaneous magneto–dielectric phase transition occurs when energy scales of the spin part and the lattice part coincide. An intermediate phase like the partial disordered phase disappears. Both systems relax frustration of the other system cooperatively and realize ordered states.View full abstractDownload PDF (225K) -
Tetsuya Sasakawa, Hiroki Miyaoka, Kazunori Umeo, Shinobu Aoyagi, Kenic ...2004 Volume 73 Issue 1 Pages 262-268
Published: January 15, 2004
Released on J-STAGE: July 25, 2007
JOURNAL RESTRICTED ACCESSBoth CeRhAs and CeRhSb are known to open a narrow pseudogap at the Fermi level. For the alloys CeRhAs1−xSbx (0≤x≤1), we report the magnetic, transport and x-ray diffraction measurements. For x=0, the orthorhombic ε-TiNiSi-type crystal structure with a 2b×2c superlattice changes to the hexagonal LiGaGe-type upon heating above 360 K, thereby the Ce chain is straightened. The phase transitions disappear upon alloying at a small level x=0.025, and alloys for 0.25≤x≤0.50 adopt the hexagonal YPtAs-type structure at room temperature. Over the wide range 0.025≤x≤0.94, no clear sign of gap is observed in either magnetic susceptibility, specific heat, resistivity or thermopower. The electronic specific heat coefficients for the end compounds at x=0 and x=1 are ten-fold increased by alloying at x=0.025 and x=0.94, respectively. These results indicate that not only the coherent hybridization of the 4f wave function with the conduction bands in the ε-TiNiSi-type structure but also the superlattice structure play important roles in the gap formation in CeRhAs.View full abstractDownload PDF (232K) -
Shinichi Itoh, Yasuo Endoh, Kazuhisa Kakurai, Hidekazu Tanaka2004 Volume 73 Issue 1 Pages 269-274
Published: January 15, 2004
Released on J-STAGE: July 25, 2007
JOURNAL RESTRICTED ACCESSInelastic neutron scattering experiments on the one-dimensional Heisenberg antiferromagnetic systems, CsNiCl3 (S=1), CsVCl3 (S=3⁄2) and CsCrCl3 (S=2), were performed, and the dispersion relation of the magnetic excitations at low temperature (E(q)) as well as the temperature dependence of the inverse magnetic correlation length (κ(T)) were measured. The observed κ(T) for each system was well fitted by the quantum theory, and the exchange constant for each system was determined from κ(T). Evaluating E(q) by using the determined exchange constants, we confirmed that the observed enhancement in the excitation energies compared with the classical excitation energies are in good agreement with the quantum renormalization factors predicted by the quantum Monte Carlo calculations.View full abstractDownload PDF (166K) -
Takeshi Waki, Harukazu Kato, Masaki Kato, Kazuyoshi Yoshimura2004 Volume 73 Issue 1 Pages 275-279
Published: January 15, 2004
Released on J-STAGE: July 25, 2007
JOURNAL RESTRICTED ACCESSThe 51V nuclear magnetic resonance and relaxation (NMR) are measured for BixV8O16 in the temperature range from 4.2 K to 280 K. The BixV8O16 system with 1.60≤x≤1.80 is known to crystallize in the Hollandite structure with a [V8O16] framework which is composed of double chains formed by edge-shared VO6 octahedra. In this system, we observed temperature-induced Metal–Insulator transition (MIT) in the composition range of 1.72≤x≤1.80. In order to reveal the mechanism of MIT in this system, 51V NMR measurements have been performed on Bi1.77V8O16 as well as on the simple Pauli paramagnetic compound Bi1.60V8O16 for a comparative study: the Knight shift K and the spin–lattice relaxation rate 1⁄T1 of 51V NMR have been measured to investigate the magnetic and electric properties. By applying the random phase approximation (RPA) method the absolute values of 1⁄T1T are analyzed in the Pauli paramagnetic regime of Bi1.77V8O16 above TMIT and Bi1.60V8O16 for whole temperature region. As a result, the modification factor K(α) for applying the RPA theory to the interacting system has been found to be 0.9 (nearly non-interacting) for the case of x=1.60 and 1.7 (antiferromagnetic) for x=1.77, implying that the antiferromagnetic spin correlation and frustration may cause the occurrence of MIT in Bi1.77V8O16.View full abstractDownload PDF (311K) -
Yoshiharu Miyajima, Haruhiko Yashiro, Takanari Kashiwagi, Masayuki Hag ...2004 Volume 73 Issue 1 Pages 280-286
Published: January 15, 2004
Released on J-STAGE: July 25, 2007
JOURNAL RESTRICTED ACCESSElectron paramagnetic resonance (EPR) measurements for frequencies from 28.5 GHz to 608.1 GHz and magnetic field up to 14 T have been performed on single crystals of sperm whale high-spin (S=5⁄2) met-myoglobin. The EPR resonance field along the c*-axis deviates from the g=5.71 straight line at high frequencies. The axial zero-field splitting constant (D) of the met-myoglobin sample is evaluated to be 9.47±0.05 cm−1 by analyzing the resonance fields with the S=5⁄2 spin Hamiltonian including the D term. The angular dependence of EPR spectra in the ab plane has been also investigated at high frequencies. Two kinds of EPR spectra are observed corresponding to two kinds of different heme sites in the unit cell. A notable change in the linewidth of the spectrum along the c*-axis occurs above 350 GHz, suggesting that the dominant relaxation process changes around 350 GHz. The origins of the linewidth are discussed.View full abstractDownload PDF (281K) -
Luis F. Da Silva2004 Volume 73 Issue 1 Pages 287-288
Published: January 15, 2004
Released on J-STAGE: July 25, 2007
JOURNAL RESTRICTED ACCESSThe photoacoustic effect, produced by the F-center in alkali halide crystals, is analyzed using the configuration coordinate model. By using the configuration coordinate model it is possible to explain the temperature increase of the sample when the sample is illuminated and the F-centers absorb light. Also this model explains the piston effect upon the atmosphere that surrounds the sample when the sample is illuminated. The temperature increase and the piston effect, produced during the development of the photoacoustic effect, cause the sound wave generation in the atmosphere that surrounds the sample when the F-centers absorb light. Using this model, the temperature increase value for a KCl sample and the displacement of the faces of the crystal during the process for the following crystals: KCl, KBr, KI and NaCl, have been determined.View full abstractDownload PDF (58K) -
Ding-wei Huang2004 Volume 73 Issue 1 Pages 289-290
Published: January 15, 2004
Released on J-STAGE: July 25, 2007
JOURNAL RESTRICTED ACCESSDownload PDF (61K) -
Yoshihiro Ishibashi, Minoru Fukui2004 Volume 73 Issue 1 Pages 291
Published: January 15, 2004
Released on J-STAGE: July 25, 2007
JOURNAL RESTRICTED ACCESSDownload PDF (38K)
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