Showing papers in "Journal of the Physical Society of Japan in 1989"
TL;DR: In this paper, a test system is assumed to interact with a heat bath consisting of harmonic oscillators or an equivalent bath with a proper frequency spectrum producing a Gaussian-Markoffian random perturbation, and the effect of reaction of the test system to the bath is considered in the high temperature approximation.
Abstract: A test system is assumed to interact with a heat bath consisting of harmonic oscillators or an equivalent bath with a proper frequency spectrum producing a Gaussian-Markoffian random perturbation. The effect of reaction of the test system to the bath is considered in the high temperature approximation. Elimination of the bath using the influence functional method of Feynman and Vernon yields a continuous fraction expression for the reduced density matrix of the test system. The result affords a basis to clarify the relationship between the stochastic and the dynamical approaches to treat the problem of partial destruction of quantum coherence of a system interacting with its environment.
787 citations
TL;DR: The dependence of the title of as mentioned in this paper originates from a singular angle dependence on the distribution width of the area of the semiclassical closed orbits under the magnetic field in the reciprocal space.
Abstract: The dependence of the title is shown to originate in a singular angle dependence of the distribution width of the area of the semiclassical closed orbits under the magnetic field in the reciprocal space. In quasi-two-dimensional metals with a cylindrical Fermi surface, the distribution width of the area of the orbits on the Fermi surface vanishes at certain inclination angles of the magnetic field, entailing the appearance of remarkable effects. The observed peaks of the coarse-grained magnetoresistance are found to correspond to these special angles.
318 citations
TL;DR: In this article, a Bacillus subtilis strain was inoculated on the plate surface and incubated at 35°C, and the colony patterns were analyzed and found to be self-similar with a fractal dimension of 1.716±0.008, in excellent agreement with the expected value of the DLA model.
Abstract: Bacteria have been shown to grow with various morphologies under different conditions on agar plates. A Bacillus subtilis strain was inoculated on the plate surface and incubated at 35°C. Colonies grew two-dimensionally with random branches, similar to clusters of the diffusion-limited aggregation (DLA) model. The colony patterns were analyzed and found to be self-similar with a fractal dimension of 1.716±0.008, in excellent agreement with the expected value of the DLA model. Interior branches were observed to stop growing in spite of their open neighborhood during the incubation period, implying the existence of a screening effect. These results clearly suggest that the colony pattern of the organism was formed through the DLA process. Moreover, the colonies were found to grow radially with almost regular branches on agar plates with moist surfaces, reminiscent of “dense radial” morphology.
238 citations
TL;DR: In this paper, Monte Carlo simulation in the ground state and at finite temperatures as well as exact diagonalization and the transfer matrix method are reported, and the short-range incommensurate spin correlation is observed and analyzed in the doped Hubbard and the t - J model both in one and two dimensions.
Abstract: Numerical results obtained from Monte Carlo simulation in the ground state and at finite temperatures as well as the exact diagonalization and the transfer matrix method are reported. Efficiency of the Monte Carlo method in the ground state is examined. Spin, charge and superconducting correlations are investigated for the Hubbard and the t - J model in one and two dimensions. The momentum distribution in the one-dimensional Hubbard model shows fermi-liquid-like behavior at least in two orders of magnitude smaller energy scale than the band width. The short-range incommensurate spin correlation is observed and analyzed in the doped Hubbard and the t - J model both in one and two dimensions. In the ground state, the superconducting correlation shows the absence of system size dependence in two dimensions at the filling smaller than 0.8 and in one dimension at any filling. The binding energy of two fermions and the spin and charge distortion around an itinerant fermion are also discussed in the t - J and th...
151 citations
TL;DR: In this article, the electronic structures of Co 2 NbSn and Ni 2 MnGa for both cubic and tetragonal structures were calculated by KKR method. And they showed that the band Jahn-Teller effect caused the lattice transformation in both alloys.
Abstract: It is known experimentally that Heusler alloys, Ni 2 MnGa and Co 2 NbSn undergo the cubic-to-tetragonal lattice transformation, in a ferromagnetic state and a paramagnetic one, respectively. We calculated electronic structures of Co 2 NbSn and Ni 2 MnGa for both cubic and tetragonal structures by KKR method. Comparing the density-of-state of the cubic and tetragonal structures for each alloy, it is expected that the band Jahn-Teller effect cause the lattice transformation in both alloys.
133 citations
129 citations
TL;DR: Spectral densities of local single-particle, magnetic and charge excitations are calculated for the impurity Anderson Hamiltonian based on the renormalization group approach as discussed by the authors, which is made in wide range of energy and for various magnitude of f -f Coulomb interaction constant.
Abstract: Spectral densities of local single-particle, magnetic and charge excitations are calculated for the impurity Anderson Hamiltonian based on the renormalization group approach. Calculation is made in wide range of energy and for various magnitude of f – f Coulomb interaction constant, U f , and for degeneracy factor from 2 to 5. The width of the peak at the Fermi level in the single-particle spectrum has always comparable scale to the magnetic excitation energy, and is never larger than the hybridization width. In the BIS side of this sharp peak a broad satellite with large intensity appears as a shoulder when U f is large and the f -electron number is intermediate larger than 1. The band-like peak in BIS of U -compounds, which has much larger width than that of the usual band theory, is interpreted by this broad satellite.
124 citations
TL;DR: In this paper, the broad resistive transition observed in high-temperature superconductors under an applied magnetic field was explained by a renormalized theory of the order parameter fluctuations.
Abstract: We attempt to explain the broad resistive transition observed in high-temperature superconductors under an applied magnetic field by a renormalized theory of the order parameter fluctuations using a model of superconductors with layered structures The results are compared with single-crystal resistivity data They are in good agreement, at least in the higher temperature side of the resistive transition, where the theory is expected to be valid
116 citations
TL;DR: In this article, a new family of high-T C superconductors (Ln 1- x Ce x ) 2 (Ba 1- y Ln y ) 2 Cu 3 O 10-δ) has been found by resistivity and magnetization measurements.
Abstract: A new family of high- T C superconductors (Ln 1- x Ce x ) 2 (Ba 1- y Ln y ) 2 Cu 3 O 10-δ (Ln: Nd, Sm, EU) has been found by resistivity and magnetization measurements. The highest onset transition temperature is about 43 K. The structure is proposed on the basis of electron diffractions and Rietveld analysis of powder X-ray diffraction data.
111 citations
TL;DR: In this article, a Ginzburg-Landau model for solid solutions is introduced to examine elastic effects near the phase separation, and the spinodal curve is calculated when the elastic moduli depend on the concentration and an external stress is applied.
Abstract: We introduce a Ginzburg-Landau model for solid solutions to examine elastic effects near the phase separation. As a first application the spinodal curve is calculated when the elastic moduli depend on the concentration and an external stress is applied. The instability is triggered by fluctuations with wave vectors in particular directions. This indicates the morphology of emerging domains,
109 citations
TL;DR: In this article, the low-temperature specific heat (1.5 K to 6 K), the electrical resistivity (1 K to room temperature) and the magnetoresistance at 1.4, 4.2 and 10 K have been measured for the single-grained I-phase of Al-Li-Cu with near 6:4:1 composition grown by the Bridgman method.
Abstract: The low-temperature specific heat (1.5 K to 6 K), the electrical resistivity (1 K to room temperature) and the magnetoresistance at 1.4, 4.2 and 10 K have been measured for the single-grained I-phase of Al–Li–Cu with near 6:4:1 composition grown by the Bridgman method. An etching method, which allows us to dissolve only the fcc Al second phase completely, was developed. The density of states at the Fermi energy obtained from the electronic specific heat coefficient is extremely small compared with the corresponding free-electron value. The resistivity at 4.2 K is as high as 870 µΩcm and decreases as \({-}{\sqrt{T}}\) below 20 K and as - T above 20 K, indicating the development of the weak localization of electrons. Magnetic field dependence of the magnetoresistance is consistent with the theory of the localization without involving electron-electron interaction.
TL;DR: In this article, a slave-fermion scheme was used, where electron operators are replaced by bose operators with auxiliary fermi operators, and the ground state by a mean field approximation with RVB order parameter for spin shows long-range antiferromagnetic order, which is incommensurate except for half-filled case.
Abstract: Square lattice Hubbard model is investigated near half-filled in the limit of large U A slave-fermion scheme is used, where electron operators are replaced by bose operators with auxiliary fermi operators The ground state by a mean field approximation with RVB order parameter for spin shows long-range antiferromagnetic order, which is incommensurate except for half-filled case
TL;DR: In this paper, an extended model of flow orientation has been developed for analyzing the inplane anisotropy in Langmuir-Blodgett (LB) films by taking into account the viscoelastic nature of a condensed monolayer at the air-water interface as a Bingham plasticity.
Abstract: An extended model of flow orientation has been developed for analyzing the inplane anisotropy in Langmuir-Blodgett (LB) films by taking into account the viscoelastic nature of a condensed monolayer at the air-water interface as a Bingham plasticity. The model is based on a two-dimensional fluid and a line-sink as representing the monolayer and the substrate, respectively. The predictions from the present model with respect to the dichroic behavior have been experimentally verified employing a mixed LB system of a merocyanine dye and a fatty acid. The model is also consistent with the remarks from ESR line-shape analysis reported previously and those from analysis of the optical absorption spectra using the extended dipole theory. These results show that the inner stress due to the velocity gradient in the monolayer during the deposition is the origin of the in-plane anisotropy.
TL;DR: In this paper, the authors considered the bilinear N -soliton solutions for the KP (two dimensional KdV) equation which utilize the Jacobi formula of the matrix algebra.
Abstract: We consider the new derivations of the bilinear N -soliton solutions for the KP (two dimensional KdV) equation which utilize the Jacobi formula of the matrix algebra. The periodic waves of explode-decay type are shown to be derived easily in the present approach. It is shown that physically important several other nonlinear equations can be cast into our present form of “four-operators” bilinear equation.
TL;DR: The crystal structure of (La 1- x Ba x ) 2 CuO 4-δ (0≤ x ≤ 0.12) was extensively investigated by powder X-ray diffraction over a wide temperature range down to 4.2 K.
Abstract: The crystal structure of (La 1- x Ba x ) 2 CuO 4-δ (0≤ x ≤0.12) was extensively investigated by powder X-ray diffraction over a wide temperature range down to 4.2 K. A structural sequence of tetragonal-orthorhombic-tetragonal phases was found on cooling for the samples with concentrations of 0.035< x <0.10. Here a new structural phase diagram is mapped in the T - x plane.
TL;DR: In this article, the effective Hamiltonian for high T c Cu-based oxide superconductors is derived based on Cu: d x 2 - y 2 and O: p σ orbitals in the Cu-O plane by taking into account the intra-and nearest-neighbor interatomic Coulomb interactions for both cases of hole and electron doping.
Abstract: The effective Hamiltonian for high- T c Cu-based oxide superconductors is derived based on Cu: d x 2 - y 2 and O: p σ orbitals in the Cu–O plane by taking into account the intra- and nearest-neighbor interatomic Coulomb interactions for both cases of hole and electron doping. For hole doping, where the stability of Cu ++ is assumed, the effective Hamiltonian proves to have various interaction processes, some features of which are studied by considering a case with a single Cu spin and one hole in the oxygen band. The spatial extent of the singlet-bound state in this case has been examined to the linear order of the oxygen band width. For electron doping the effective Hamiltonian is much simpler and essentially the same as the t - J model. Based on these results we discuss the relevance of the t - J model to the high- T c Cu oxides. The effects of Cu: d 3 z 2 - r 2 orbitals and O: p z orbitals at the apex of the pyramid or octahedron are also examined.
TL;DR: In this article, the authors analyzed the multiplet structures due to the Cu 2 p -XPS in La 2 CuO 4, CuO and Cu dihalides using the single-site Anderson model with five filled bands.
Abstract: In this study we analyze the Cu 2 p -XPS in La 2 CuO 4 , CuO and Cu dihalides using the single-site Anderson model with five filled bands. We take into account the multiplet coupling between a Cu 3 d hole and a core hole, and the anisotropic hybridization between the 3 d hole and O 2 p valence band holes. As a result we show that the multiplet structures due to the Cu (2 p ) 5 (3 d ) 9 electron configuration are strongly affected by the anisotropy of the hybridization.
TL;DR: In this paper, the authors investigated the double transition phenomenon in a typical heavy Fermion material UPt 3 and showed that there exists a non-trivial coupling term between the preexisting spin density wave order parameter and the superconducting pairing function belonging to a degenerate representation with internal degree of freedom.
Abstract: The origin of the double transition phenomenon recently found in a typical heavy Fermion material UPt 3 is investigated. It is shown group-theoretically solely on the basis of the known symmetries that there exists a non-trivial coupling term between the preexisting spin density wave order parameter and the superconducting pairing function belonging to a degenerate representation with internal degree of freedom. This coupling ultimately leads to the T c splitting. Superconducting properties associated with this unconventional pairing function, including the phase diagram, are discussed both in the absence and presence of an applied field. Several experiments are proposed to test the present theory, in particular, the field dependence of the double transition is crucial to identify the symmetry of the pairing function. The existing data are most consistent with those in the two-dimensional representations E 1 g or E 1 u of the hexagonal symmetry. The possibility of similar phenomenon in other heavy Fermion...
TL;DR: In the quark-shell model, there is no qualitative reason why the "dihyperon" or "H dibaryon" should be quasi-stable or even stable.
Abstract: A super-hypernucleus is a nucleus which consists of many strange quarks as well as up and down quarks. An important part of the results of our recent investigation on the mass spectrum and other properties of super-hypernuclei in the quark-shell model is reported. It is expected that not only certain exotic nuclei such as the “dideltas” (Dδ ++++ and Dδ - ) but also certain super-hypernuclei such as the “hexalambda” (Hλ) and the “vigintiquattuoralambda” (Vqλ) may appear as quasi-stable nuclei. However, in the quark-shell model, there is no qualitative reason why the “dihyperon” or “H dibaryon” (H) should be quasi-stable or even stable. Many other predictions including a sudden increase of the K/π ratio due to the production of super-hypernuclei in heavy-ion collisions at high energies are also made.
TL;DR: In this paper, the slave-fermion method is applied to the model in the limit of large U at half-filled, where the model reduces to the antiferromagnetic Heisenberg model.
Abstract: A nearly half-filled two-dimensional Hubbard model has been considered as a model for a high transition temperature oxide superconductor. A new scheme to treat this model, the slave-fermion method, is proposed. The method is applied to the model in the limit of large U at half-filled, where the model reduces to the antiferromagnetic Heisenberg model. It is shown that the ground state energy becomes much lower in the slave-fermion scheme than that in the slave-boson scheme. The ground state shows antiferromagnetic long range order at T =0.
TL;DR: In this article, the angular dependence of the de Haas-van Alphen (dHvA) frequency has been studied in the Kondo lattice compound CeB 6.
Abstract: The angular dependence of the de Haas-van Alphen (dHvA) frequency has been studied in the Kondo lattice compound CeB 6 . The Fermi surface of CeB 6 is quite similar to that of PrB 6 or LaB 6 , with an electron pocket of almost the same size as that in PrB 6 . We have also determined the field dependence of the heavy cyclotron mass for the main belly orbit in CeB 6 and have confirmed a discrepancy between the present mass and the one estimated from the low temperature specific heat coefficient.
TL;DR: In this paper, the authors proposed the following integral equation for solving the BKP equations in the bilinear form, which plays the same role as that of the Gel'fand-Levitan integral equation used in solving the KP (Kadomtsev-Petviashvili) equation.
Abstract: We propose the following integral equation for solving the BKP equations \begin{aligned} K(x, z)+F(x, z)-\int_{-\infty}^{x}D_{y}K(x, y)\cdot F(y, z)\text{d}y=0 \end{aligned} where F ( x , y ) satisfies the linear differential equation \begin{aligned} \left( \frac{\partial}{\partial x_{n}} - \frac{\partial ^{n}}{\partial x^{n}} - \frac{\partial ^{n}}{\partial y^{n}} \right) F(x, y)=0 \quad \text{for odd $n$}, \end{aligned} with the conditions F ( x , y )=- F ( y , x ) and F ( x , -∞)=0. The τ-function, solution to the BKP equations in the bilinear form is related to the solution K ( x , y ) of the integral equation through the relation \begin{aligned} \frac{\partial}{\partial y} K(x, y)|_{y=x} = \frac{\partial}{\partial x} \log \tau(x). \end{aligned} The integral equation plays the same role as that of the Gel'fand-Levitan integral equation used in solving the KP (Kadomtsev-Petviashvili) equation.
TL;DR: In this article, photo-acoustic spectroscopy, ESR and EXAFS measurements have been carried out on the Se chains isolated in the channels of mordenite crystal with 6.7 A diameter.
Abstract: Photoacoustic spectroscopy, ESR and EXAFS measurements have been carried out on the Se chains isolated in the channels of mordenite crystal with 6.7 A diameter. The optical gap is estimated to be 2.3 eV at room temperature, which is much larger than that of trigonal Se. At low temperatures, illumination with the light having energy near or above the optical gap induces new absorption bands at 1.85 and 2.25 eV, which are associated with paramagnetic defects. Higher energy light (>2.9 eV) shifts the absorption edge to lower energy. The fluctuations in the covalent bond length increase with illumination, though the helical chain structure is preserved. These changes vanish by annealing at room temperature. The phenomena are reversible in the illumination and annealing cycle. The photo-induced absorption and the edge shift are reduced when the induced bands are excited optically.
TL;DR: In this article, the Laplace transforms of correlation functions are expressed in terms of continued fractions of relevant hyperoperators, and the result is valid to all orders of the system-bath interaction.
Abstract: Two-time correlation functions of physical operators of a system interacting with a heat bath producing a Gaussian-Markoffian noise are treated with the use of Feynman-Vernon's influence functional formalism. The Laplace transforms of correlation functions are shown to be expressed in terms of continued fractions of relevant hyperoperators. The result is valid to all orders of the system-bath interaction. In the limitation of motional narrowing, it reduces to those obtained in conventional methods.
TL;DR: In this paper, the effect of the charge differentiation introduced by the substitution of Sr for La has been attributed to the presence of 63/65 Cu resonances due to nonequivalent Cu sites.
Abstract: Nuclear magnetic/quadrupole resonance (NMR/NQR) has been observed for the Cu nuclei in La 2- x Sr x CuO 4 . NMR measurements have been carried out for the powdered sample whose c axes are aligned. No evidence for magnetic ordering was observed down to 1.3 K. Instead, the existence of two sets of 63/65 Cu resonances due to nonequivalent Cu sites has been concluded from the results of spectrum and relaxation measurements at low temperatures. These resonances are ascribed to the effect of the charge differentiation introduced by the substitution of Sr for La.
TL;DR: In this article, the decay time of stretch-oriented poly(phenylenevinylene) (PPV) was studied in the temperature range 300∼12 K. The luminescence spectrum is composed of vibronic bands and a broad band, which are interpreted as caused by radiative annihilation of free and selftrapped excitons.
Abstract: Integrated luminescence spectra, time-resolved luminescence spectra, and luminescence decay times of stretch-oriented poly(phenylenevinylene) (PPV) are studied in the temperature range 300∼12 K. The reflectance spectrum at room temperature is also studied. The luminescence spectrum is composed of vibronic bands and a broad band, which are interpreted as caused by radiative annihilation of free and selftrapped excitons, respectively. Temperature dependence of the intensity of free-exciton luminescence and temperature dependence of the decay time are interpreted in terms of relaxation of excitons. The height of a potential barrier, which separates the free exciton state and the self-trapped state, is found to be 350 cm -1 . At 20 K, exciton relaxation toward the self-trapped state occurs by a quantum-mechanical tunneling process. The tunneling rate obtained is (90 ps) -1 .
TL;DR: In this paper, a closed container subject to vertical oscillation is studied and nonlinear dynamical equations of two nearly degenerate subharmonic modes responding to the external forcing are derived, using the averaged Lagrangian method for slowly varying amplitudes Stability and bifurcation diagrams are shown for the system with linear damping Period-doubling bifurlcation and chaotic solutions with one positive Lyapunov characteristic exponent are obtained numerically.
Abstract: Surface waves in a closed container subject to vertical oscillation are studied Nonlinear dynamical equations of two nearly degenerate subharmonic modes responding to the external forcing are derived, using the averaged Lagrangian method for slowly varying amplitudes Stability and bifurcation diagrams are shown for the system with linear damping Period-doubling bifurcation and chaotic solutions with one positive Lyapunov characteristic exponent are obtained numerically It is shown that some of the period-doubling bifurcations are related to the symmetry of the dynamical system
TL;DR: The spectrum of light scattered from poly (N-isopropylacrylamide) (NIPA) chains (molecular weight M W ∼ 1.3×10 6 ) in water has been investigated as a function of temperature by using photon correlation spectroscopy as mentioned in this paper.
Abstract: The spectrum of light scattered from poly (N-isopropylacrylamide) (NIPA) chains (molecular weight M W ∼1.3×10 6 ) in water has been investigated as a function of temperature by using photon correlation spectroscopy. In a dilute solution (27 µg/cm 3 ) we observed a sharp change in polymer size that corresponds to a coil-globule transition of a single polymer chain. The transition occurred at 34.1°C, accompanied by a sharp decrease in hydrodynamic radius from 1000 to 600 A as the temperature was increased. In a semi-dilute solution (2.7 mg/cm 3 ) a phenomenon of critical slowing down in the polymer concentration fluctuations was observed around the phase separation temperature, which is very similar to the previous observation on NIPA/water gel.
TL;DR: In this article, the diamagnetic alignment of polymerized organic molecules is discussed both from the theoretical and experimental points of view, and it is shown that when a number of molecules aggregate with their diamagnetic principal axes along the same direction, the resultant diamagnetic anisotropy energy becomes comparable to the thermal energy and the aggregated molecule can align under a conventional magnetic field, even at room temperatures.
Abstract: Diamagnetic alignment of polymerized organic molecules is discussed both from the theoretical and experimental points of view. When a number of molecules aggregate with their diamagnetic principal axes along the same direction, the resultant diamagnetic anisotropy energy becomes comparable to the thermal energy and the aggregated molecule can align under a conventional magnetic field, even at room temperatures. Polymerization of fibrin molecules is observed under magnetic fields up to 8 Tesla and considerable alignment is found. Partial alignment is seen even at 1 Tesla which means that blood clotting is influenced by use of the conventional superconducting magnet.
TL;DR: In this article, the effect of long-range Coulomb interaction between an electron and a hole on the optical absorption spectrum of a one-dimensional Peierls insulator is studied theoretically.
Abstract: The effect of long-range Coulomb interaction between an electron and a hole on the optical absorption spectrum of a one-dimensional Peierls insulator is studied theoretically. Energy levels and oscillator strengths of exciton states in the Peierls gap and the line shape of the continuous spectrum (interband transitions) above the gap are calculated by taking the interatomic nature of the optical transition matrix element into account. The effect turns out to be of great significance, in the sense that even a very weak interaction induces an anomalously large oscillator strength of the lowest exciton ( n =0) state.