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Volume 75, Issue 1
Displaying 1-50 of 51 articles from this issue
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Yoshinori Tokura2006 Volume 75 Issue 1 Pages 011001
Published: January 15, 2006
Released on J-STAGE: August 27, 2009
JOURNAL RESTRICTED ACCESSFor many years, photoinduced phase transition (PIPT) phenomena have been investigated to generate a hidden state of matter by means of optically excited states and achieve a ultrafast optical switching on a large scale. Strategies to explore PITP materials are presented along with the early history of PIPT studies.View full abstractDownload PDF (84K) -
Eric Collet, Marylise Buron-Le Cointe, Hervé Cailleau2006 Volume 75 Issue 1 Pages 011002
Published: January 15, 2006
Released on J-STAGE: August 27, 2009
JOURNAL RESTRICTED ACCESSLaser driven solid--solid phase transition is a new kind of manipulation of matter by light which offers fascinating possibilities for controlling the switching of the physical properties of materials at the macroscopic state. This is possible by taking advantage of the cooperative interactions between the constituent molecules of the material. Slow dynamics phenomena are illustrated by the photo-induced spin transition, where long lived states can be generated at low temperature using cw excitation. A fast process is exemplified here by the neutral--ionic phase transition induced in a transient state on the 100-picosecond time-scale by a 100 femtosecond laser pulse. Self-amplification and self-ordering processes are discussed.View full abstractDownload PDF (290K) -
Andrei S. Mishchenko, Naoto Nagaosa2006 Volume 75 Issue 1 Pages 011003
Published: January 15, 2006
Released on J-STAGE: August 27, 2009
JOURNAL RESTRICTED ACCESSWe present recent advances in understanding of the ground and excited states of the electron–phonon coupled systems obtained by novel methods of Diagrammatic Monte Carlo and Stochastic Optimization, which enable the approximation-free calculation of Matsubara Green function in imaginary times and perform unbiased analytic continuation to real frequencies. We analyze Rashba–Pekar exciton–polaron as a classic example of a system with self-trapping crossover and demonstrate basic features of the phenomenon. Analysis of unconventional self-trapping cases, such as Jahn–Teller driven crossover in one-dimensional systems and magnon-assisted localization in cuprates, is presented. Results on the optical conductivity of the Fröhlich polaron are also discussed.View full abstractDownload PDF (509K) -
A. Cavalleri, M. Rini, R. W. Schoenlein2006 Volume 75 Issue 1 Pages 011004
Published: January 15, 2006
Released on J-STAGE: August 27, 2009
JOURNAL RESTRICTED ACCESSWe review our work on the photo-induced insulator–metal transition in the strongly-correlated, spin-Peierls compound VO2. Our pump-probe experiments exploit the full spectral range of modern femtosecond science, combining time-resolved mid-IR and visible techniques with ultrafast soft x-ray absorption and hard x-ray diffraction. We also report on the switching behavior of VO2 nanoparticles embedded in Silica or in optical fibers, a new route to incorporate complex, photo-active materials into technologically viable environments.View full abstractDownload PDF (325K) -
Shin-ya Koshihara, Shin-ichi Adachi2006 Volume 75 Issue 1 Pages 011005
Published: January 15, 2006
Released on J-STAGE: August 27, 2009
JOURNAL RESTRICTED ACCESSThe search for materials that show a phase transition triggered by weak external stimulation of light is an important and attractive target for photonic and materials science. We review experimental evidence indicating that photo-injected local excitation can really trigger an electron–lattice coupled cooperative phenomenon called photo-induced phase transition (PIPT). We discuss the dynamical nature of electron (spin)–lattice-coupled changes in π-conjugated polymer crystals, organic transition metal complexes, and organic A2B charge transfer complexes. We also review the development of ultra-fast X-ray technology in collaboration with work in the fields of quantum electronics and synchrotron radiation, which are essential for the promotion of the future study of PIPT.View full abstractDownload PDF (537K) -
D. J. Hilton, R. P. Prasankumar, S. A. Trugman, A. J. Taylor, R. D. Av ...2006 Volume 75 Issue 1 Pages 011006
Published: January 15, 2006
Released on J-STAGE: August 27, 2009
JOURNAL RESTRICTED ACCESSIt is now possible to routinely generate and detect subpicosecond pulses in the mid and far-infrared portions of the electromagnetic spectrum enabling novel time-resolved spectroscopic investigations. In the context of complex materials, spectral selectivity from approximately 0.001–1.0 eV is especially important since many relevant quasiparticle excitations lie in this range. This includes, as examples, gapped excitations related to superconductivity, charge ordering, and hybridization phenomena, phonon and polaron dynamics, and the coherent Drude response so intimately related to metal–insulator transitions. Temporally resolving spectral changes associated with such excitations in pump-probe-like experiments is proving to be a powerful tool in materials where multiple degrees of freedom (charge, lattice, spin, and orbital) conspire to determine functionality. Quite generally, important insights into ground state properties, coupling parameters, degrees of freedom influencing quasiparticle transport, the nature of phase transitions, and nonequilibrium dynamics can be obtained. Following a brief review of illustrative examples highlighting such possibilities we will present, in some detail, recent experiments on two different ferromagnetic materials. First, we describe terahertz emission experiments on single crystal iron thin films. Following photoexcitation, a burst of coherent THz radiation is emitted which is shown to be consistent with partial demagnetization of the Fe film occurring on a picosecond timescale. As a second example, we describe recent optical-pump infrared-probe measurements on the low carrier density magnetoresistive pyrochlore Tl2Mn2O7. In the ferromagnetic and paramagnetic phases, the recombination of photoexcited carriers is strongly influenced by spin fluctuations.View full abstractDownload PDF (346K) -
Shinichiro Iwai, Hiroshi Okamoto2006 Volume 75 Issue 1 Pages 011007
Published: January 15, 2006
Released on J-STAGE: August 27, 2009
JOURNAL RESTRICTED ACCESSOne-dimensional (1D) correlated electron systems are good targets for the exploration of photoinduced phase transitions (PIPTs). This is because photocarrier generations and/or charge transfer (CT) excitations by lights can stimulate instabilities inherent to the 1D nature of electronic states through strong electron–electron interactions and electron(spin)–lattice interactions. In this paper, we review the ultrafast dynamics of three typical PIPTs observed in 1D correlated electron systems: 1) a photoinduced transition from a Mott insulator to a metal in a halogen-bridged Ni-chain compound, [Ni(chxn)2Br]Br2 (chxn = cyclohexanediamine); 2) a photoinduced melting of a spin-Peierls phase in an organic CT compound, K-tetracyanoquinodimethane (TCNQ); 3) a photoinduced transition between neutral (N) and ionic (I) states in an organic CT compound, tetrathiafulvalene-p-chloranil (TTF-CA). The primary dynamics of these PIPTs are discussed on the basis of the results of femtosecond pump–probe spectroscopy.View full abstractDownload PDF (899K) -
Kenji Yonemitsu, Keiichiro Nasu2006 Volume 75 Issue 1 Pages 011008
Published: January 15, 2006
Released on J-STAGE: August 27, 2009
JOURNAL RESTRICTED ACCESSTheories of photoinduced phase transitions have developed along with the progress in experimental studies, especially concerning their nonlinear characters and transition dynamics. At an early stage, paths from photoinduced local structural distortions to global ones are explained in classical statistical models. Their dynamics are governed by transition probabilities and inevitably stochastic, but they were sufficient to describe coarse-grained time evolutions. Recently, however, a variety of dynamics including ultrafast ones are observed in different electronic states. They are explained in relevant electronic models. In particular, a coherent lattice vibration and coherent motion of a macroscopic domain boundary need appropriate interactions among electrons and lattice displacements. Furthermore, some transitions proceed almost in one direction, which can be explained by considering relevant electronic processes. We describe the history of theories of photoinduced phase transitions and discuss a future perspective.View full abstractDownload PDF (171K) -
M. Fushiki2006 Volume 75 Issue 1 Pages 013001
Published: January 15, 2006
Released on J-STAGE: August 27, 2009
JOURNAL RESTRICTED ACCESSThe matrix elements corresponding to the collision term in the Boltzmann equation for dilute hard spheres were calculated with a computer algebra system and the fast Fourier transform, and utilized to solve the 10th-order Chapman–Enskog (CE) expansion for a steady heat-transfer problem. The solution of the CE expansion was examined using the results of the direct simulation Monte Carlo method and was shown to be a good approximation in the region of moderate Knudsen number.View full abstractDownload PDF (104K) -
Xianguo Geng, Huihui Dai2006 Volume 75 Issue 1 Pages 013002
Published: January 15, 2006
Released on J-STAGE: August 27, 2009
JOURNAL RESTRICTED ACCESSA hierarchy of new nonlinear differential-difference equations associated with a 3×3 matrix spectral problem is proposed. The generalized Hamiltonian structures for the hierarchy are derived with the aid of trace identity.View full abstractDownload PDF (83K) -
Youhei Fujitani2006 Volume 75 Issue 1 Pages 013401
Published: January 15, 2006
Released on J-STAGE: August 27, 2009
JOURNAL RESTRICTED ACCESSVelocity continuity and force balance are usually required at the interface of two fluid phases in conventional hydrodynamics, where the viscosity is assumed to be constant in a single fluid phase. These boundary conditions connect the pressure and velocity fields across the interface. An alternative way to achieve this connection, where the viscosity is assumed to smoothly change across a thin interfacial region, was proposed to facilitate the numerical study of colloidal dynamics. We study the steady Stokes flow in and around a single droplet by use of the smoothened viscosity, imposing a purely extensional flow far from the droplet. In the limit of the thin interfacial region, we analytically obtain a set of connection formulas, which yields the fields that are different from those obtained in conventional hydrodynamics unless the droplet is a rigid body.View full abstractDownload PDF (98K) -
Miwako Takahashi, Ananda Kumar Das, Reo Nakamura, Hiroshi Iwasaki, Toe ...2006 Volume 75 Issue 1 Pages 013601
Published: January 15, 2006
Released on J-STAGE: August 27, 2009
JOURNAL RESTRICTED ACCESSUsing the pulsed-neutron diffraction technique, we performed in situ measurements of structural ordering in the ternary alloy CuMnPt6. The diffraction patterns at various temperatures give a direct observation of a double-step ordering: disorder to Cu3Au type order as an ordering within the fundamental face-centered cubic lattice to subdivide the lattice into two sublattices formed by face-centered sites (first sublattice) and corner sites (second sublattice) at 968°C; and Cu3Au type order to ABC6 type order as an ordering within the second sublattice to subdivide the lattice further into two sublattices formed by alternating (111) planes at 746°C. The order parameters for the ABC6 type structure experimentally estimated by the method of static concentration waves indicate that the primary ordering developed almost completely, but the secondary ordering remained incomplete.View full abstractDownload PDF (156K) -
Daisuke Saeki, Tsutomu Hamada, Kenichi Yoshikawa2006 Volume 75 Issue 1 Pages 013602
Published: January 15, 2006
Released on J-STAGE: August 27, 2009
JOURNAL RESTRICTED ACCESSWe investigated the kinetics of domain growth on liposomes caused by decreasing the temperature; the liposomes consisted of a ternary mixture (unsaturated phospholipid, saturated phospholipid, and cholesterol). The domain-growth process was monitored by fluorescence microscopy, and the growth was mediated by fusing the domains through collisions. It was found that an average domain size r develops with time t as r∼t0.15. This indicates that the exponent is about half of that deduced from the theoretical analysis of a model of the Brownian motion on a two-dimensional membrane. We discuss the mechanism of the experimental scaling behavior by considering the elasticity of the membrane.View full abstractDownload PDF (196K) -
Manabu Takahashi, Junichi Igarashi2006 Volume 75 Issue 1 Pages 013701
Published: January 15, 2006
Released on J-STAGE: August 27, 2009
JOURNAL RESTRICTED ACCESSWe propose X-ray diffraction analyses exploiting the L-edge resonant scattering in the spin density wave (SDW) phase of Cr metal. We predict that strong signals could be detected on satellite spots corresponding to the charge density wave (CDW), by an ab initio band structure calculation. The sinusoidal modulation of spin moment makes the SDW exchange potential different from site to site, and accordingly the 3d density of states (DOS) locally varies. The signal detects this modulation in the unoccupied part of the local 3d DOS. This new mechanism predicts the signal detectable even in the absence of CDW ordering. Analyzing the energy profile, we demonstrate that the L-edge RXS is a sensitive probe for studying unoccupied 3d states.View full abstractDownload PDF (131K) -
Katsunori Kubo, Takashi Hotta2006 Volume 75 Issue 1 Pages 013702
Published: January 15, 2006
Released on J-STAGE: August 27, 2009
JOURNAL RESTRICTED ACCESSEffects of orbital degeneracy on magnetic susceptibility in paramagnetic phases are investigated within a mean-field theory. Under certain crystalline electric fields, the magnetic moment consists of two independent moments, e.g., spin and orbital moments. In such a case, the magnetic susceptibility is given by the sum of two different Curie–Weiss relations, leading to deviation from the Curie–Weiss law. Such behavior may be observed in d- and f-electron systems with t2g and Γ8 ground states, respectively. As a potential application of our theory, we attempt to explain the difference in the temperature dependence of magnetic susceptibilities of UO2 and NpO2.View full abstractDownload PDF (105K) -
Hiroshi Kontani2006 Volume 75 Issue 1 Pages 013703
Published: January 15, 2006
Released on J-STAGE: August 27, 2009
JOURNAL RESTRICTED ACCESSWe study AC conductivities in high-Tc cuprates, which offer us significant information to determine the true ground states. We take the current vertex correction (CVC) into account correctly to satisfy the conservation laws in terms of the fluctuation-exchange (FLEX) approximation. The significant role of the CVC on the optical Hall conductivity [σxy(ω)] is confirmed in the presence of strong antiferromagnetic (AF) fluctuations. This fact leads to the failure of the relaxation time approximation (RTA). As a result, experimental highly unusual behaviors, (i) prominent ω and temperature dependences of the optical Hall conductivity and the optical Hall coefficient [RH(ω)], and (ii) a simple Drude form of the optical Hall angle [θH(ω)] for a wide range of ω, are satisfactorily reproduced. In conclusion, both DC and AC transport phenomena in (slightly under-doped) high-Tc cuprates can be explained comprehensively in terms of a nearly AF Fermi liquid, without assuming an exotic ground state.View full abstractDownload PDF (195K) -
Osamu Suzuki, Hiroyuki S. Suzuki, Hideaki Kitazawa, Giyuu Kido, Takafu ...2006 Volume 75 Issue 1 Pages 013704
Published: January 15, 2006
Released on J-STAGE: August 27, 2009
JOURNAL RESTRICTED ACCESSWe performed ultrasonic measurement on the rare-earth intermetallic compound PrInAg2 to examine the quadrupolar Kondo effect associated with the non-Kramers Γ3 doublet ground state. The characteristic softening of the elastic constant (c11−c12)⁄2 below 10 K in PrInAg2 is attributed to the Curie term in quadrupolar susceptibility for the quadrupole O22=Jx2−Jy2 of the stable Γ3 ground state. (c11−c12)⁄2 turns to a slight increase with the −lnT dependence below 0.1 K, which suggests the quenching of the quadrupolar moment in the quadrupolar Kondo state. Under applied magnetic fields of 10 T and 15 T above 8.7 T corresponding to the Kondo temperature TK of ∼0.86 K, the behavior of (c11−c12)⁄2 is described in terms of quadrupolar susceptibility for the stable 4f2 state.View full abstractDownload PDF (1163K) -
Riki Jindo, Shigeharu Sugawara, Naoya Tajima, Hiroshi M. Yamamoto, Rei ...2006 Volume 75 Issue 1 Pages 013705
Published: January 15, 2006
Released on J-STAGE: August 27, 2009
JOURNAL RESTRICTED ACCESSWe investigated the magnetoresistance effect on an organic conductor, (ET)3Cl(DFBIB), which has a quasi-two-dimensional electron system. The out-of-plane resistivity in transverse magnetic fields was found to obey a simple formula that was derived by Schofield and Cooper [Phys. Rev. B 62 (2000) 10779]: ρ⊥(B)=ρ⊥(0)\\sqrt1+βB2, where ρ⊥(B) is the magnetic field (B)-dependent resistivity and β is a parameter that depends on the material and the temperature. To our knowledge, this is the first example of quasi-two dimensional metals, the magnetoresistance of which is explained by an analytical formula in wide ranges of temperature and magnetic field.View full abstractDownload PDF (106K) -
Gaku Motoyama, Suguru Yamamoto, Hiroaki Takezoe, Yasukage Oda, Ko-ichi ...2006 Volume 75 Issue 1 Pages 013706
Published: January 15, 2006
Released on J-STAGE: August 27, 2009
JOURNAL RESTRICTED ACCESSWe measured the dc magnetization, electrical resistivity, and ac magnetic susceptibility of a series of polycrystalline CePt3Si samples whose compositions vary slightly from the stoichiometric composition. The sample that showed the most distinct antiferromagnetic transition at 2.2 K was found to be Ce1.01Pt3Si annealed. This sample showed a clear bulk antiferromagnetic order at 2.2 K even in both electrical resistivity and dc magnetization measurements, although the characteristic change in dc magnetization at 2.2 K was found to be small and to be easily masked in other magnetic anomalies if they exist. Moreover, it had the largest residual resistivity ratio. We concluded that Ce1.01Pt3Si annealed has the intrinsic bulk properties of ideal CePt3Si. In addition, we revealed that some anomalies arise as a result of the variation in composition. One is a ferromagnetic anomaly at 3.0 K in the Pt-rich samples, and the other is an antiferromagnetic anomaly at 4.0 K in the Pt-poor samples. The two magnetic anomalies seemed to appear in small domains in the samples that exhibited an antiferromagnetic order at 2.2 K. To reveal the relationship between these magnetisms and superconductivity, we measured ac magnetic susceptibility down to ∼14 mK. We found that the superconducting transition temperature is suppressed by the ferromagnetic anomaly.View full abstractDownload PDF (146K) -
Toshikazu Nakamura, Ko Furukawa, Toshifumi Hara2006 Volume 75 Issue 1 Pages 013707
Published: January 15, 2006
Released on J-STAGE: August 27, 2009
JOURNAL RESTRICTED ACCESS13C NMR measurements were performed for a one-dimensional organic conductor, (TMTTF)2ReO4. The existence of an intermediate charge ordering (CO) phase was clarified for a TMTTF salt with a Td symmetry counter anion by the 13C NMR absorption line and spin–lattice relaxation rate, 13C T1−1. The 13C NMR spectra, which are characteristic of nuclei in equivalent molecules at room temperature, indicated two inequivalent molecules with unequal electron densities below 225 K. Moreover, the spin-singlet transition associated with ReO4 anion ordering was confirmed at around 158 K by 13C NMR. The 13C NMR lines show a marked change at 158 K. The possible redistribution of the electronic charge at the anion ordering temperature as well as the origin of the charge ordering phenomena are discussed.View full abstractDownload PDF (256K) -
Yoshihiko Ihara, Kenji Ishida, Hideo Takeya, Chishiro Michioka, Masaki ...2006 Volume 75 Issue 1 Pages 013708
Published: January 15, 2006
Released on J-STAGE: August 27, 2009
JOURNAL RESTRICTED ACCESSThe Co Knight shift was measured in an aligned powder sample of NaxCoO2·yH2O, which shows superconductivity at Tc∼4.6 K. The Knight-shift components parallel (Kc) and perpendicular to the c-axis (along the ab plane Kab) were measured in both the normal and superconducting (SC) states. The temperature dependences of Kab and Kc are scaled with the bulk susceptibility, which shows that the microscopic susceptibility deduced from the Knight shift is related to Co-3d spins. In the SC state, the Knight shift shows an anisotropic temperature dependence: Kab decreases below 5 K, whereas Kc does not decrease within experimental accuracy. This result raises the possibility that spin-triplet superconductivity with the spin component of the pairs directed along the c-axis is realized in NaxCoO2·yH2O.View full abstractDownload PDF (296K) -
Mamoru Yogi, Hidekazu Mukuda, Yoshio Kitaoka, Shin Hashimoto, Takashi ...2006 Volume 75 Issue 1 Pages 013709
Published: January 15, 2006
Released on J-STAGE: August 27, 2009
JOURNAL RESTRICTED ACCESSWe report the measurements of the 29Si Knight shift 29K on the noncentrosymmetric heavy-fermion compound CePt3Si in which antiferromagnetism (AFM) with TN=2.2 K coexists with superconductivity (SC) with Tc=0.75 K. Its spin part 29Ks, which is deduced to be Ksc≥0.11 and 0.16% at respective magnetic fields H=2.0061 and 0.8671 T, does not decrease across the superconducting transition temperature Tc for the field along the c-axis. The temperature dependence of nuclear spin–lattice relaxation of 195Pt below Tc has been accounted for by a Cooper pairing model with a two-component order parameter composed of spin-singlet and spin-triplet pairing components. From this result, it is shown that the Knight-shift data are consistent with the occurrence of the two-component order parameter for CePt3Si.View full abstractDownload PDF (184K) -
Kenya Ohgushi, Shigeki Miyasaka, Yoshinori Tokura2006 Volume 75 Issue 1 Pages 013710
Published: January 15, 2006
Released on J-STAGE: August 27, 2009
JOURNAL RESTRICTED ACCESSThe anomalous Hall effect (AHE) was investigated for a single crystal of 6% Ag-doped FeCr2S4 with the rotation of the magnetic field (H) within the yz plane (the current along \\hatx, the Hall voltage along \\haty). We observed a clear deviation from the cosθ dependence (θ being the angle between H and \\hatz), which indicates the presence of an anisotropic AHE. We analyzed a tight-binding model of the diamond lattice with the Dzyaloshinskii–Moriya interaction and reproduced the characteristic experimentally observed features. The quantum topology nature of the AHE is revealed in this compound.View full abstractDownload PDF (248K) -
Yutaka Itoh, Chishiro Michioka, Kazuyoshi Yoshimura, Yutaka Ueda2006 Volume 75 Issue 1 Pages 013711
Published: January 15, 2006
Released on J-STAGE: August 27, 2009
JOURNAL RESTRICTED ACCESSWe report a 63Cu nuclear quadrupole resonance (NQR) study of the vortex state for an aligned polycrystalline sample of a slightly overdoped high-Tc superconductor YBa2Cu3O7−δ (Tc∼92 K) at a low magnetic field of 96 mT along the c axis, near a lower critical field Hc1. We observed the frequency distribution of the nuclear spin-lattice relaxation time 63T1 in a Zeeman-perturbed 63Cu NQR spectrum below Tc. The characteristic behavior of 1/63T1 with respect to temperature and frequency suggests the role of antiferromagnetic spin fluctuations in the Doppler-shifted quasiparticle energy spectrum inside and outside vortex cores.View full abstractDownload PDF (172K) -
Satoshi Morita, Yukiyasu Ozeki, Hidetoshi Nishimori2006 Volume 75 Issue 1 Pages 014001
Published: January 15, 2006
Released on J-STAGE: August 27, 2009
JOURNAL RESTRICTED ACCESSThe gauge theory for random spin systems is extended to quantum spin glasses to derive a number of exact and/or rigorous results. The transverse Ising model and the quantum gauge glass are shown to be gauge invariant. For these models, an identity is proved that the expectation value of the gauge invariant operator in the ferromagnetic limit is equal to the one in the classical equilibrium state on the Nishimori line. As a result, a set of inequalities for the correlation function are proved, which restrict the location of the ordered phase. It is also proved that there is no long-range order in the two-dimensional quantum gauge glass in the ground state. The phase diagram for the quantum XY Mattis model is determined.View full abstractDownload PDF (125K) -
Qing Liu, Jia-Min Zhu, Hong-Yu Wu2006 Volume 75 Issue 1 Pages 014002
Published: January 15, 2006
Released on J-STAGE: August 27, 2009
JOURNAL RESTRICTED ACCESSA Wick-type stochastic Korteweg–de Vries equation is researched. We establish a relationship between the Korteweg–de Vries equation and the elliptic equation. With the help of Hermit transformation and the elliptic equation mapping method, we obtain a series of exact Jacobi elliptic function solutions to the stochastic Korteweg–de Vries equation in the white noise environment.View full abstractDownload PDF (96K) -
Kouji Ueda, Tomotoshi Nishino, Kouichi Okunishi, Yasuhiro Hieida, Rene ...2006 Volume 75 Issue 1 Pages 014003
Published: January 15, 2006
Released on J-STAGE: August 27, 2009
JOURNAL RESTRICTED ACCESSWe present a construction of a matrix product state (MPS) that approximates the largest-eigenvalue eigenvector of a transfer matrix T of a two-dimensional classical lattice model. A state vector created from the upper or the lower half of a finite size cluster approximates the largest-eigenvalue eigenvector. Decomposition of this state vector into the MPS gives a way of extending the MPS recursively. The extension process is a special case of the product wave function renormalization group (PWFRG) method, that accelerates the numerical calculation of the infinite system density matrix renormalization group (DMRG) method. As a result, we successfully give the physical interpretation of the PWFRG method, and obtain its appropriate initial condition.View full abstractDownload PDF (176K) -
Shen Shuifa, Wang Fengge, Gu Jiahui, Liu Yujuan, Tang Bin, Jiang Weizh ...2006 Volume 75 Issue 1 Pages 014201
Published: January 15, 2006
Released on J-STAGE: August 27, 2009
JOURNAL RESTRICTED ACCESSThe decay of molybdenum-101 has been investigated using the three-parameter (γ–γ–t) coincidence system of HPGe–HPGe detectors. According to the off-line analysis, the decay scheme was modified. The positions of 221.80, 318.00, 377.90, 452.50, 515.42, 1011.05, and 1759.72 keV transitions have been arranged again, the transition positions of 104.70, 105.95, and 774.15 keV gamma rays have been assigned for the first time, the positions of 169.00, 590.91, 980.52, and 1431.68 keV transitions have been reconfirmed, and the 1508.01 keV gamma ray was observed simultaneously for the first time and its transition position has been assigned. The β− intensities and the values of logft of most levels were calculated. Combining with the high-spin states observed by the in-beam γ-ray spectroscopy of previous decay works, the structure of the excited positive/negative-parity yrast states of 101Tc is discussed using a projected shell model, and a band diagram calculated for the positive-parity yrast band is also shown in order to extract physics out of the numerical results. In addition, the analysis of other three bands originated from 3/2−[301], 5/2−[303], and 1/2+[431] Nilsson states, respectively, is also performed in the framework of this model.View full abstractDownload PDF (219K) -
Miki Wadati, Naoshi Tsuchida2006 Volume 75 Issue 1 Pages 014301
Published: January 15, 2006
Released on J-STAGE: August 27, 2009
JOURNAL RESTRICTED ACCESSPropagations of nonlinear waves in the quasi-one dimensional F=1 spinor Bose–Einstein condensates are studied. The three-component macroscopic wavefunction obeys a generalized Gross–Pitaevskii equation (nonlinear Schrödinger equation). Plane wave and solitary wave solutions are obtained explicitly. It is shown that the analysis of the plane waves leads to a classification of solitary waves, which are known as polar solitons and ferromagnetic solitons.View full abstractDownload PDF (76K) -
Keiji Kosaka2006 Volume 75 Issue 1 Pages 014302
Published: January 15, 2006
Released on J-STAGE: August 27, 2009
JOURNAL RESTRICTED ACCESSThe optimized effective potential (OEP) method in the density functional theory is reformulated on the basis of the variable coupling constant scheme. By this formulation, the origin of the so-called ‘orbital shift’ in the OEP method is revealed. The method leads to a simple iterative procedure of the OEP method using the Thomas–Fermi model. This method is extended to the OEP method in the current density functional theory (CDFT) and in the time-dependent CDFT. As a numerical test, the procedure in the nonmagnetic time-independent case is applied to the exchange-only calculation of the Be atom. The present procedure converges more quickly than that of Kümmel and Perdew [Phys. Rev. B 68 (2003) 035103].View full abstractDownload PDF (136K) -
An Integrable Three Particle System Related to Intrinsic Localized Modes in Fermi–Pasta–Ulam-β ChainBao-Feng Feng2006 Volume 75 Issue 1 Pages 014401
Published: January 15, 2006
Released on J-STAGE: August 27, 2009
JOURNAL RESTRICTED ACCESSIn this paper, a ring of three particles interacting via nearest-neighbor harmonic and quartic potentials is investigated for the study of intrinsic localized modes (ILMs) in Fermi–Pasta–Ulam (FPU) atomic chain. In spite of the fact that above Hamiltonian system has been shown to be integrable by Hietaniata [Phys. Rep. 147 (1987) 87], Yoshida and Ramani [Physica D 30 (1988) 151], respectively, we approve its integrability in a more straightforward way. Moreover, we obtain exact periodic solutions in terms of the Jacobi elliptic functions for both the zero and nonzero third first integral. The significance of these findings lies in the fact that analytical stationary and moving ILMs solutions are obtained, and a close relationship between the movability of ILMs and the third first integral is clarified.View full abstractDownload PDF (177K) -
Hiroyuki Yoshimoto, Susumu Kurihara2006 Volume 75 Issue 1 Pages 014601
Published: January 15, 2006
Released on J-STAGE: August 27, 2009
JOURNAL RESTRICTED ACCESSThe effects of collective modes on the thermoelectric properties of a charge density system is studied. We derive the temperature dependences of thermoelectric power and thermal conductivity by applying the linear response theory to the Fröhlich Hamiltonian. Energy dissipation has been attributed to the nonlinear interaction between the phase mode and the amplitude mode, ignoring disorder effects. We have found that the temperature dependence of the correlation function between electrical and heat currents is the same as that of the correlation function between electrical currents. This implies that thermoelectric power is inversely proportional to temperature. We have also found that the temperature dependences of all correlation functions are essentially determined by the same mechanism—nonlinear amplitude-phase interaction. The thermal conductivity is nearly constant at a temperature above the amplitude mode gap, and is exponentially low at a temperature sufficiently below it.View full abstractDownload PDF (154K) -
Eiichi Matsuoka, Shouta Narazu, Katsuyuki Hayashi, Kazunori Umeo, Tosh ...2006 Volume 75 Issue 1 Pages 014602
Published: January 15, 2006
Released on J-STAGE: August 27, 2009
JOURNAL RESTRICTED ACCESSThe magnetic, transport and thermal properties of alkaline-earth-filled skutterudites AOs4Sb12 (A=Sr, Ba) are reported. The strong temperature dependence of the magnetic susceptibility and the moderately high value of the temperature linear coefficient of specific heat [45 mJ/(mol K2)] indicate the presence of a large density of states derived from Os 5d states near the Fermi level. The lattice thermal conductivity κph does not show a peak near 50 K and its value is much smaller than those of the Fe- and Ru-counterparts. This unusual behavior of κph is attributed to the phonon scattering by localized vibrations of A2+ ions in the oversized cage of Os4Sb12. We propose that the strong electron–phonon interaction in the presence of tunneling states is the origin for the shoulder observed in the electrical resistivity around 100 K.View full abstractDownload PDF (284K) -
Hiroyasu Tanaka, Hironori Kawashima, Hisamitsu Iizuka, Hideaki Fukuda, ...2006 Volume 75 Issue 1 Pages 014701
Published: January 15, 2006
Released on J-STAGE: August 27, 2009
JOURNAL RESTRICTED ACCESSSimilarity is observed in the deviation of Hall resistance from the quantized value with the increase in the source–drain current ISD in our butterfly-type Hall bars and in the Hall bars used by Jeanneret et al. [IEEE Trans. Instrum. Meas. 44 (1995) 254], while changes in the diagonal resistivity ρxx with ISD are significantly different between these Hall bars. The temperature dependence of the critical Hall electric field Fcr(T) for the collapse of RH(4) measured in these Hall bars is approximated using Fcr(T)=Fcr(0)(1−(T⁄Tcr)2). Here, the critical Hall electric field at zero temperature depends on the magnetic field B as Fcr(0)∝B3⁄2. Theoretical considerations are given on Fcr(T) on the basis of a temperature-dependent mobility edge model and a schema of temperature-dependent inter-Landau level tunneling probability arising from the Fermi distribution function. The former does not fit in with the ISD dependence of activation energy in ρxx.View full abstractDownload PDF (261K) -
Morio Miyazawa2006 Volume 75 Issue 1 Pages 014702
Published: January 15, 2006
Released on J-STAGE: August 27, 2009
JOURNAL RESTRICTED ACCESSWe propose a possible strategy of calculating physical quantities in normal states of Ce compounds, in the presence of a crystalline electric field (CEF). In particular, we show the specific heat γ and magnetic susceptibility χ cannot be estimated without correctly treating the CEF splitting and renormalization effect due to electron correlation. In the study, we discuss CeCoIn5 as a typical example, and estimate γ and χ on the basis of the tight binding model which is suitable for CeCoIn5. Throughout the paper, we show how to treat electron correlation in order to construct a renormalized electronic structure. Using the renormalized electronic structure, we obtain reasonable values for physical quantities.View full abstractDownload PDF (303K) -
Oki Miura, Takeo Fujiwara2006 Volume 75 Issue 1 Pages 014703
Published: January 15, 2006
Released on J-STAGE: August 27, 2009
JOURNAL RESTRICTED ACCESSWe apply the dynamical mean field theory (DMFT) combined with the iterative perturbation theory (IPT) to the doubly degenerate eg and the triply degenerate t2g bands on a simple cubic lattice and a body-centered cubic lattice and calculate the spectrum and optical conductivity in arbitrary electron occupation. The spectrum simultaneously shows the effects of multiplet structure together with the electron ionization and affinity levels of different electron occupations, coherent peaks at the Fermi energy in the metallic phase and an energy gap at an integer filling of electrons for sufficiently large Coulomb U. We also discuss the critical value of the Coulomb U for degenerate orbitals on a simple cubic lattice and a body-centered cubic lattice.View full abstractDownload PDF (2070K) -
Syuma Yasuzuka, Keizo Murata, Harukazu Yoshino, Tsutomu Fujimoto, Masa ...2006 Volume 75 Issue 1 Pages 014704
Published: January 15, 2006
Released on J-STAGE: August 27, 2009
JOURNAL RESTRICTED ACCESSRecently, a conductive coordination compound [Cu(TANC)](F)0.5 with new radical frameworks was synthesized, where TANC stands for 5,6,11,12-tetraazanaphacene. We have measured the electrical resistivity of [Cu(TANC)](F)0.5 under high pressures up to 8.0 GPa. At ambient pressure, the temperature dependence of the resistivity shows semiconducting behavior described by a variable range hopping conduction, ρ(T)∼exp(T0⁄T)η. The value of T0 increases with increasing pressure up to 6.5 GPa, beyond which it decreases abruptly. The pressure dependence of T0 is discussed in terms of the increase of the pureness of one-dimensionality and the strength of the random potential due to disordered F− ions.View full abstractDownload PDF (195K) -
Shigeki Fujiyama, Toshikazu Nakamura2006 Volume 75 Issue 1 Pages 014705
Published: January 15, 2006
Released on J-STAGE: August 27, 2009
JOURNAL RESTRICTED ACCESSWe report 13C NMR spectra and nuclear spin lattice relaxation rate 1⁄T1 for a quasi-one-dimensional quarter-filled organic material (TMTTF)2AsF6, which undergoes charge ordering (TCO=102 K) and spin-Peierls phase transitions (TSP=14 K). The ratio of two 1⁄T1 for the charge accepting and donating TMTTF sites which grows from TCO finally saturates in approaching TSP, indicating one spin correlation function even in the charge ordered state. Below TSP, however, the doubly split NMR lines from inequivalently charged molecules merge into one line, originated from the variation in charge densities. This shows that a rearrangement of the charge configuration occurs at TSP.View full abstractDownload PDF (176K) -
Masafumi Sera, Shinya Goto, Tatsurou Koshikawa, Moo-Sung Kim, Hideki T ...2006 Volume 75 Issue 1 Pages 014706
Published: January 15, 2006
Released on J-STAGE: August 27, 2009
JOURNAL RESTRICTED ACCESSWe measured the thermal expansion and magnetostriction of PrB6 under the longitudinal magnetic fields up to 15 T for three magnetic field directions. We found the following results in the IC1 and IC2 phases for H||⟨111⟩. The magnetostriction shows only a small magnetic field dependence in the IC1 phase but exhibits a large shrinkage with increasing magnetic field roughly proportional to −H2 in the IC2 phase. The thermal expansion exhibits a small change in the IC1 phase but a large increase in the IC2 phase with decreasing temperature. These different behaviors between the IC1 and IC2 phases originate from the existence of both χ|| and χ⊥ components exist in the IC1 phase and only the χ⊥ component in the IC2 phase. The characteristic magnetic and magnetoelastic properties of the experimental results are reproduced by the simple calculation for the two sublattice model, although this model does not represent the incommensurate magnetic strucutres of PrB6. The important point is the weight of χ|| and χ⊥ components which determines the macroscopic properties such as the magnetization, magnetostriction and thermal expansion.View full abstractDownload PDF (357K) -
Ichiro Tamura, Tsuyoshi Ikeno, Toshio Mizushima, Yosikazu Isikawa2006 Volume 75 Issue 1 Pages 014707
Published: January 15, 2006
Released on J-STAGE: August 27, 2009
JOURNAL RESTRICTED ACCESSWe prepared two YbFe4Sb12 samples (#1 and #2) and a LaFe4Sb12 sample. Mössbauer and magnetization measurements were performed on the samples at various temperatures and in applied magnetic fields. The experimental results indicate that #1 is in a weakly ferromagnetic state below 13 K, while #2 is in an itinerant paramagnetic state even at 2 K, and that quadrupole splitting for #1 at each temperature is slightly less than that for #2. Therefore, we conclude that YbFe4Sb12 is an intermediate material between a nearly ferromagnetic material and a weakly ferromagnetic material.View full abstractDownload PDF (175K) -
Hiroki Kudo, Masato Kitaya, Hajime Kobayashi, Masanobu Shirai, Koichir ...2006 Volume 75 Issue 1 Pages 014708
Published: January 15, 2006
Released on J-STAGE: August 27, 2009
JOURNAL RESTRICTED ACCESSGreen and red emissions were observed by pumping Mn-doped MgGa2O4 crystals, respectively, at the band edge below 300 nm and between 300 and 500 nm. These responses are in contrast to those in the case of Mn-doped MgAl2O4. We propose a model of these luminescence channels by taking account of the smaller band gap of MgGa2O4 than that of MgAl2O4, and the ESR spectrum showing Mn2+ located at Ga-sites.View full abstractDownload PDF (172K) -
Mikito Koga, Masashige Matsumoto, Hiroyuki Shiba2006 Volume 75 Issue 1 Pages 014709
Published: January 15, 2006
Released on J-STAGE: August 27, 2009
JOURNAL RESTRICTED ACCESSA possibility of exciton-mediated mechanism is studied to describe the superconductivity in a Pr skutterudite PrOs4Sb12. In this compound the low-lying crystal-field states of Pr form a pseudo-quartet consisting of Γ1 singlet ground and Γ4(2) triplet excited states. The dispersive crystal-field excitations (excitons) have been detected experimentally. The conduction electrons couple both magnetically and nonmagnetically with the pseudo-quartet. Believing that this coupling should be crucial for various properties of PrOs4Sb12, we determine the effective interaction between conduction electrons and the Pr pseudo-quartet states. It turns out that the nature of exchange processes is related closely to au and tu components of the conduction electrons that correspond to the molecular orbitals of an Sb12 cage surrounding a Pr ion. By the second-order perturbation in the exchange coupling, Cooper pairing interactions are derived both for singlet and triplet superconductivities. First, they are classified with cubic point-group (Oh) bases. Then, the Th symmetry, which is a unique feature of the filled skutterudite compounds, is taken into account; it is shown that the gap functions in different Oh representations are mixed due to the Th symmetry. The Th symmetry in which no fourfold symmetry is present shows up in the gap functions within a weak coupling theory. As a candidate for the superconductivity in PrOs4Sb12, we propose a nonunitary triplet state with twofold symmetry which agrees most naturally with the gap structure observed in the low field phase. We also find that the triplet superconducting state becomes possible owing to the Th crystal-field symmetry.View full abstractDownload PDF (5411K) -
Masato Kaneko, Masao Ogata2006 Volume 75 Issue 1 Pages 014710
Published: January 15, 2006
Released on J-STAGE: August 27, 2009
JOURNAL RESTRICTED ACCESSCharge ordering phenomenon in θ-(BEDT-TTF)2X is studied by using 1/4-filled extended Hubbard model on an anisotropic triangular lattice through mean-field approximation. It is found that a metallic charge ordered state with 3-periodicity on lattices (3-fold type charge order) is realized in the realistic parameter region where the nearest neighbor Coulomb interaction Vij is nearly isotropic. This 3-fold state survives up to high temperatures by estimating the free energy. Insulating state with diagonal or vertical-type charge ordering appears as increasing anisotropy of Vij. Considering the effect of the structural distortion observed in θ-(BEDT-TTF)2RbZn(SCN)4 at low temperatures, horizontal-type charge ordered insulating phase tends to be stabilized and the region where 3-fold type exists becomes narrower. Our results are consistent with the metallic state with long periodic charge order which can be related to 3-fold type in θ-(BEDT-TTF)2RbZn(SCN)4 at high temperatures and insulating state with horizontal charge order at low temperatures. For θ-(BEDT-TTF)2CsZn(SCN)4, we speculate several kinds of charge-ordered states are energetically competing with each other leading to an inhomogeneous state at low temperatures.View full abstractDownload PDF (183K) -
Kai. Xuan, X. H. Yan, S. L. Ding, Y. R. Yang, Y. Xiao, Z. H. Guo2006 Volume 75 Issue 1 Pages 014711
Published: January 15, 2006
Released on J-STAGE: August 27, 2009
JOURNAL RESTRICTED ACCESSRandomly-aligned ZnO hexagonal nanoprisms were fabricated by using catalyst-free chemical vapor deposition (CFCVD) in a double-tube system. The growth mechanism is attributed to vapor–solid mechanism. The absence of metal catalyst nanoparticles on the top of nanoprisms ensures a real field emission from ZnO nanostructures. The artificial defects arising from HF acid etching on Si(111) substrate serve as the nuclei centers. It is shown that the emission current density of 1 mA/cm2 is obtained at 6.6 V/μm macroscopic electric field. The field enhancement factor (γ=3000) is far larger than the theoretical value (γ=205), which implies that the dominating contributions can be attributed to the pyramidal salients other than the whole crests of hexagonal nanoprisms.View full abstractDownload PDF (268K) -
Yutaka Nishimura, Taksu Cheon, Petr Šeba2006 Volume 75 Issue 1 Pages 014801
Published: January 15, 2006
Released on J-STAGE: August 27, 2009
JOURNAL RESTRICTED ACCESSWe investigate a simple multisegment cellular automaton model of traffic flow. With the introduction of segment-dependent acceleration probability, metastable congested states in the intermediate density region emerge, and the initial-state dependence of the flow is observed. The essential feature of three-phased structure empirically found in real-world traffic flow is reproduced without elaborate assumptions.View full abstractDownload PDF (401K) -
Takashi Ozawa, Isao Suzuki, Hirohiko Sato2006 Volume 75 Issue 1 Pages 014802
Published: January 15, 2006
Released on J-STAGE: August 27, 2009
JOURNAL RESTRICTED ACCESSStructural, magnetic, and transport properties of a novel hollandite-type molybdenum oxide, Rb1.5Mo8O16 have been investigated. Whereas a typical hollandite structure is characterized by uniform zigzag ladder chains of edge-shared MO6 (M=transition metal) octahedra, the zigzag ladders in Rb1.5Mo8O16 are strongly distorted, and consequently, “Mo4” clusters composed of four edge-shared MoO6 octahedra are formed. A semiquantitative band calculation based on an extended Hückel method shows that the band structure assumes the characteristics of the molecular orbitals of an isolated Mo4 cluster. The magnetic susceptibility reveals the existence of spins spread over each Mo4 cluster rather than localized on each Mo atom. The electrical resistivity and the thermoelectric power indicate that the electric conduction is governed by cluster-to-cluster electron hopping. Rb1.5Mo8O16 undergoes a phase transtion at T1=208 K, accompanied by a change in the number of spins and carriers. X-ray diffractions at low temperatures detected a slight breakdown of the tetragonal symmetry below T1. The transport and the magnetic properties of related compounds, K2Mo8O16 and Ba1.14Mo8O16 are also reported.View full abstractDownload PDF (554K) -
Kazuki Kanki, Damien Loison, Klaus-Dieter Schotte2006 Volume 75 Issue 1 Pages 015001
Published: January 15, 2006
Released on J-STAGE: August 27, 2009
JOURNAL RESTRICTED ACCESSDownload PDF (75K) -
Akira Oosawa, Yoichi Nishiwaki, Tetsuya Kato, Kazuhisa Kakurai2006 Volume 75 Issue 1 Pages 015002
Published: January 15, 2006
Released on J-STAGE: August 27, 2009
JOURNAL RESTRICTED ACCESSDownload PDF (122K) -
Seong-Min Yoon, Kyungsik Kim, T. Odagaki2006 Volume 75 Issue 1 Pages 015003
Published: January 15, 2006
Released on J-STAGE: August 27, 2009
JOURNAL RESTRICTED ACCESSDownload PDF (70K) -
Yoichi Tanaka, Norio Kawakami2006 Volume 75 Issue 1 Pages 015004
Published: January 15, 2006
Released on J-STAGE: August 27, 2009
JOURNAL RESTRICTED ACCESSDownload PDF (132K)