Dynamic phase transitions and dynamic phase diagrams of the Blume–Emery–Griffiths model in an oscillating field: the effective-field theory based on the Glauber-type stochastic dynamics

Using the effective-field theory based on the Glauber-type stochastic dynamics (DEFT), we investigate dynamic phase transitions and dynamic phase diagrams of the Blume–Emery–Griffiths model under an oscillating magnetic field. We presented the dynamic phase diagrams in (T/J, h₀/J), (D/J, T/J) and (K/J, T/J) planes, where T, h₀, D, K and z are the temperature, magnetic field amplitude, crystal–field interaction, biquadratic interaction and the coordination number. The dynamic phase diagrams exhibit several ordered phases, coexistence phase regions and special critical points, as well as re-entrant behavior depending on interaction parameters. We also compare and discuss the results with the results of the same system within the mean-field theory based on the Glauber-type stochastic dynamics and find that some of the dynamic first-order phase lines and special dynamic critical points disappeared in the DEFT calculation.     

ZnCdTe-ZnTe多量子阱的光泵受激发射

本文报导了ZnCdTe-ZnTe多量子阱的受激发射机理.阈值时(J_th)受激发射峰相对于激子吸收峰的能量差(19meV)与激子束缚能接近.激发光强度在3J_th～4.8J_th之间变化时,该能量差随激发光强度的变化规律与激子-激子散射过程的理论结果符合得很好,从而把该材料在上述激发光强内的受激发射机理归结为激子-激子散射过程.     

Relative stability of homochiral and heterochiral dialanine peptides. Effects of perturbation pathways and force-field parameters on free energy calculations

The relative stability of homochiral (D,D or L,L) and heterochiral (D,L or L,D) dipeptides may have been a decisive factor in the evolutionary propagation of a symmetry-breaking event leading to the present-day predominance of L-amino acids in natural proteins. Kinetic resolution in the solid-phase peptide synthesis of blocked dialanine suggests the activation free energy difference of formation of (D,D or L,L)- and (D,L or L,D)-dialanine to be 0.22?kJ?mol^?1 in favour of the formation of the homochiral dipeptide. Computer simulation studies were performed on water-solvated dialanine, applying a thermodynamic integration protocol using the GROMOS force field. Five different pathways and three force-field parameter sets have been used to assess the possibility of a computational prediction of the chiral preference. Inversion of the configuration around either one of the C_α-atoms by changing the improper dihedral angle with concomitant relaxation of the bond angles, leads to an excellent reproduction of the experimental result.     

An exact formulation of the Blume-Emery-Griffiths model on a two-fold Cayley tree model

A two-fold Cayley tree graph with fully q-coordinated sites is constructed and the spin-1 Ising Blume-Emery-Griffiths model on the constructed graph is solved exactly using the exact recursion equations for the coordination number q = 3. The exact phase diagrams in (kT/J, K/J ) and (kT/J, D/J) planes are obtained for various values of constants D/J and K/J, respectively, and the tricritical behavior is found. It is observed that when the negative biquadratic exchange (K) and the positive crystal-field (D) interactions are large enough, the tricritical point disappears in the (kT/J, K/J) plane. On the other hand, the system always exhibits a tricritical behavior in the phase diagram of (kT/J, D/J) plane. Received 8 June 2001 and Received in final form 28 September 2001     

Dynamic hysteresis behaviors in the kinetic Ising system on triangular lattice

We studied dynamic hysteresis behaviors of the spin-1 Blume-Capel (BC) model in a triangular lattice by means of the effective-field theory (EFT) with correlations and using Glauber-type stochastic dynamics. The effects of the exchange interaction (J), crystal field (D), temperature (T) and oscillating frequency (w) on the hysteresis behaviors of the BC model in a triangular lattice are investigated in detail. Results are compared with some other dynamic studies and quantitatively good agreement is found.     

Differential Entropy and Dynamics of Uncertainty

We analyze the functioning of Gibbs-type entropy functionals in the time domain, with emphasis on Shannon and Kullback-Leibler entropies of time-dependent continuous probability distributions. The Shannon entropy validity is extended to probability distributions inferred from L ²(R ⁿ ) quantum wave packets. In contrast to the von Neumann entropy which simply vanishes on pure states, the differential entropy quantifies the degree of probability (de)localization and its time development. The associated dynamics of the Fisher information functional quantifies nontrivial power transfer processes in the mean, both in dissipative and quantum mechanical cases. PACS NUMBERS: 05.45.+b, 02.50.-r, 03.65.Ta, 03.67.-a     

Fisher Information of Free-Electron Landau States

An electron in a constant magnetic field has energy levels, known as the Landau levels. One can obtain the corresponding radial wavefunction of free-electron Landau states in cylindrical polar coordinates. However, this system has not been explored so far in terms of an information-theoretical viewpoint. Here, we focus on Fisher information associated with these Landau states specified by the two quantum numbers. Fisher information provides a useful measure of the electronic structure in quantum systems, such as hydrogen-like atoms and under some potentials. By numerically evaluating the generalized Laguerre polynomials in the radial densities, we report that Fisher information increases linearly with the principal quantum number that specifies energy levels, but decreases monotonically with the azimuthal quantum number m. We also present relative Fisher information of the Landau states against the reference density with m=0, which is proportional to the principal quantum number. We compare it with the case when the lowest Landau level state is set as the reference.     

A high level computational study of the CH4/CF4 dimer: how does it compare with the CH4/CH4 and CF4/CF4 dimers?

The interaction within the methane–methane (CH₄/CH₄), perfluoromethane–perfluoromethane (CF₄/CF₄) methane–perfluoromethane dimers (CH₄/CF₄) was calculated using the Hartree–Fock (HF) method, multiple orders of Møller–Plesset perturbation theory [MP2, MP3, MP4(DQ), MP4(SDQ), MP4(SDTQ)], and coupled cluster theory [CCSD, CCSD(T)], as well as the PW91, B97D, and M06-2X density functional theory (DFT) functionals. The basis sets of Dunning and coworkers (aug-cc-pVxZ, x?=?D, T, Q), Krishnan and coworkers [6-311++G(d,p), 6-311++G(2d,2p)], and Tsuzuki and coworkers [aug(df, pd)-6-311G(d,p)] were used. Basis set superposition error (BSSE) was corrected via the counterpoise method in all cases. Interaction energies obtained with the MP2 method do not fit with the experimental finding that the methane–perfluoromethane system phase separates at 94.5?K. It was not until the CCSD(T) method was considered that the interaction energy of the methane–perfluoromethane dimer (?0.69?kcal?mol^?1) was found to be intermediate between the methane (?0.51?kcal?mol^?1) and perfluoromethane (?0.78?kcal?mol^?1) dimers. This suggests that a perfluoromethane molecule interacts preferentially with another perfluoromethane (by about 0.09?kcal?mol^?1) than with a methane molecule. At temperatures much lower than the CH₄/CF₄ critical solution temperature of 94.5?K, this energy difference becomes significant and leads perfluoromethane molecules to associate with themselves, forming a phase separation. The DFT functionals yielded erratic results for the three dimers. Further development of DFT is needed in order to model dispersion interactions in hydrocarbon/perfluorocarbon systems.     

Higher order bulk characteristic parameters of asymmetric nuclear matter

The bulk parameters characterizing the energy of symmetric nuclear matter and the symmetry energy defined at normal nuclear density ρ ₀ provide important information on the equation of state (EOS) of isospin asymmetric nuclear matter. While significant progress has been made in determining some lower order bulk characteristic parameters, such as the energy E ₀(ρ ₀) and incompressibility K ₀ of symmetric nuclear matter as well as the symmetry energy E _sym(ρ ₀) and its slope parameter L, yet the higher order bulk characteristic parameters are still poorly known. Here, we analyze the correlations between the lower and higher order bulk characteristic parameters within the framework of Skyrme Hartree-Fock energy density functional and then estimate the values of some higher order bulk characteristic parameters. In particular, we obtain J ₀ = (−355±95) MeV and I ₀ = (1473±680) MeV for the thirdorder and fourth-order derivative parameters of symmetric nuclear matter at ρ ₀ and K _sym = (−100 ± 165) MeV, J _sym = (224 ± 385) MeV, I _sym = (−1309 ± 2025) MeV for the curvature parameter, third-order and fourth-order derivative parameters of the symmetry energy at ρ ₀, using the empirical constraints on E ₀(ρ ₀), K ₀, E _sym(ρ ₀), L, and the isoscalar and isovector nucleon effective masses. Furthermore, our results indicate that the three parameters E ₀(ρ ₀), K ₀, and J ₀ can reasonably characterize the EOS of symmetric nuclear matter up to 2ρ ₀ while the symmetry energy up to 2ρ ₀ can be well described by E _sym(ρ ₀), L, and K _sym.

     

Effect of the Dzyaloshinskii-Moriya interaction on heat conductivity in one-dimensional quantum Ising chains

The effect of the Dzyaloshinskii-Moriya (DM) interaction on the heat conduction in the quantum Ising chain has been studied by solving the Lindblad master equation. The chain is subject to a uniform transverse field h, while the exchange couplings {J _m } between the nearest-neighbor spins are either uniform, random or quasi-periodic. The average energy-density profile and the average energy current in the non-equilibrium steady state have been numerically calculated. The ballistic transport is observed in the uniform Ising chain with DM interaction. For the random Ising chain with DM interaction, the energy gradient is observed in the bulk of the spin chain whose energy current appears to scale as the system size ⟨Q⟩ ∼ exp(βN) with β < 0. For the quasi-periodic Ising chain with DM interaction, the J _m takes the two values J _A and J _B arranged in the Fibonacci sequence. The energy gradient also exists in the spin chain and the energy current behaves as ⟨Q⟩ ∼ N ^α with α < 0. By increasing the strength of the DM interaction D, a non-trivial transition from the thermal insulator heat transport to anomalous heat conduction is found in the Fibonacci Ising chain with large ratio of couplings λ = J _A /J _B . A rough phase diagram of λ vs. D is given in this paper as well.     

Analyses of 4f11 Energy Levels and Transition Intensities Between Stark Levels of Er3+ in Y3Al5O12

ABSTRACT

Absorption and fluorescence spectra obtained at temperatures as low as 4 K were investigated between 200 and 1550 nm on samples containing approximately 1.2 at. wt. % Er in Y₃Al₅O₁₂ (YAG). Within this wavelength range 125 experimental energy (Stark) levels were analyzed, representing data that span 29 ^2S+1 L _J multiplet manifolds of Er³⁺(4f¹¹) in D₂ sites up to an energy of 44,000 cm^?1. Agreement between calculated and observed Stark levels was achieved with an r.m.s. deviation of 11.2 cm^?1. These transitions originate from the ground-state Stark level in the ⁴I_15/2 manifold to J + 1/2 Stark levels associated with each of the 28 excited-state manifolds. A total of 88 ground-state absorption transition line strengths were measured for 19 ^2S+1 L _J multiplet manifolds between 280 and 1550 nm. For line strength measurements, the Er³⁺ ion is assumed to be distributed homogeneously throughout the D₂ cation sites of Y³⁺ in the lattice. The line strengths were analyzed with a weighted (E _i  ? C _i )/E _i , with an r.m.s. error of 0.25. Use of a “vector crystal field” parametrization resolves ambiguities in the transition intensity parameters and allows for the definition of polarization-resolved Judd-Ofelt parameters, which may have wide-ranging applicability for future Judd-Ofelt-type intensity calculations.     

Jump diffusion coefficient of different cations intercalated into amorphous WO3

This work shows how the combination of quasi-equilibrium (chronopotentiometry) and kinetical measurements (electrochemical impedance) is able to extract ionic mobility values like the jump diffusion coefficient D_J. Results are presented on the jump diffusion coefficient variation with composition of several cations (Li⁺, Na⁺, and K⁺) intercalated into electron beam evaporation-prepared a-WO₃ thin films. D_J exhibits higher values for the smallest ion (Li⁺), and decreases as the ion size enlarges. In all cases D_J shows lower values for high intercalation levels. It is noted that the type of cation rather influences transport mechanisms than equilibrium properties (insertion thermodynamics). The energy barrier of ion hopping is analyzed in light of available microscopic diffusion models and theoretical simulations.     

Propagation characteristics of the laser-generated lower-order lamb waves in one-dimensional periodic thin plates

Using the finite element method (FEM), we study the thermoelastic generation and the transmitted power spectra (TPS) of Laser-generated lower-order Lamb wave mode in an one-dimensional thin aluminum plate engraved by a periodic rectangular grating. The calculation verified that the equally good Lamb waves band gaps can also exist in an one-component periodic structure and the width and location of the band gaps can be regulated by the parameters of the depth of the grooves (h), the ratio of the lattice period to the plate thickness (D/L) and the ratio of the width of the grooves to the lattice period (d/D). Specially, we suggest that Lamb wave band gaps can be substantially enlarged by using multiple periodic systems which consist of several pieces of periodic structure with different D/L.     

Interactions of charmed mesons with nucleons in the ¯<Emphasis Type="Italic">p</Emphasis><Emphasis Type="Italic">d</Emphasis> reaction

We study the possibility to measure the elastic ΦN (Φ≡J/ψ,ψ(2S), ψ(3770), χ_2c) scattering cross section in the reaction ˉp+d→Φ+n _sp and the elastic D(ˉD)N scattering cross section in the reaction ˉp+d→D ⁻ D ⁰ p _sp. Our studies indicate that the elastic scattering cross sections can be determined for Φ momenta about 4–6 GeV/c and D/ˉD momenta 2–5 GeV/c by selecting events with p _t≥ 0.4 GeV/c for Φ's and p _t(p _sp) ≥ 0.5 GeV/c for D/ˉD-meson production. Received: 8 November 1999     

The Dynamics of the Energy of a Kähler Class

The energy of a Kähler class, on a compact complex manifold (M,J) of Kähler type, is the infimum of the squared L²-norm of the scalar curvature over all Kähler metrics representing the class. We study general properties of this functional, and define its gradient flow over all Kähler classes represented by metrics of fixed volume. When besides the trivial holomorphic vector field of (M,J), all others have no zeroes, we extend it to a flow over all cohomology classes of fixed top cup product. We prove that the dynamical system in this space defined by the said flow does not have periodic orbits, that its only fixed points are critical classes of a suitably defined extension of the energy function, and that along solution curves in the Kähler cone the energy is a monotone function. If the Kähler cone is forward invariant under the flow, solutions to the flow equation converge to a critical point of the class energy function. We show that this is always the case when the manifold has a signed first Chern class. We characterize the forward stability of the Kähler cone in terms of the value of a suitable time dependent form over irreducible subvarieties of (M,J). We use this result to draw several geometric conclusions, including the determination of optimal dimension dependent bounds for the squared L²-norm of the scalar curvature functional.Acknowledgement We would like to thank Nicholas Buchdahl for helpful conversations leading us to several improvements of an earlier version of the article, including the correction of two improper assertions.     

Ab initio determination of the torsional spectra of acetic acid

The torsional potential energy surface and the favourite geometries of acetic acid are determined with MP4/cc-p VTZ ab initio calculations. The molecule shows two planar trans and cis conformers whose energy difference is 1882.7 cm^?1. Both minimum energy geometries are separated by a barrier of 4432.1 cm^?1. The most stable trans-conformer shows a quite low methyl torsion barrier of 169.8 cm^?1. The roto-torsional energy levels have been calculated up to J = 10. The two torsional fundamental frequencies of the trans-conformer, the methyl and the OH torsion are 82.857 (A²) and 77.050cm^?1 (E) and 568.532 (A²) and 568.418cm^?1 (E). The V₃ barrier causes a splitting of 0.315cm^?1 in the ground vibrational state where the quartic centrifugal distortion constants have been predicted to be D_J = 90.4kHz, D_JK = ?301.5kHz and D_K = 165.4kHz. Finally, the far-infrared spectra of two isotopomers have been simulated from ab initio calculations.     

A comparative photoluminescence study on Mn-Free GaAs/AlAs and Mn-containing Ga1-xMnxAs/AlAs quantum wells (QWs) grown on various orientations by MBE

Optical properties of diluted magnetic semiconductor Ga_0.999Mn_0.001As/AlAs quantum well structures grown on (1?0?0?), (1?1?0), (3?1?1)B and (4?1?1)B by molecular beam epitaxy are reported. Temperature-dependent spectral photoluminescence (PL) measurement was performed at temperatures between 15 and 300 K. The PL measurements showed that band gap of the alloy decreases with increasing lattice temperature regardless the growth orientations. S-shaped temperature dependence has been observed in the samples grown on (1?0?0), (3?1?1)B, (4?1?1)B orientations. PL emission energy is fitted with Varshni and Bose–Einstein Approximation to determine Debye temperature (β), (Θ_E) and thermal expansion coefficient (α), the exciton–phonon coupling strength (a_B).     

Representation of complex number imaginary unit and supermatrix solution to the Yang-Baxter equation

The double complex number imaginary unitJ _D is treated as a special matrixM(J _D ); by considering the matrixM(ε) corresponding to the hyperbolic complex imaginary unit ε, a supermatrix solution to the Yang-Baxter equation is constructed.     

The anisotropic 3D Ising model

An expression for the free energy of an (001) oriented domain wall of the anisotropic 3D Ising model is derived. The order--disorder transition takes place when the domain wall free energy vanishes. In the anisotropic limit, where two of the three exchange energies (e.g. J_x and J_y ) are small compared to the third exchange energy (J_z ), the following asymptotically exact equation for the critical temperature is derived, sinh(2J_z /k _B T _c)sinh(2(J_x ?+?J_y )/k _B T _c))?=?1. This expression is in perfect agreement with a mathematically rigorous result (k _B T _c/J_z ?=?2[ln(J_z /(J_x ?+?J_y ))?ln(ln(J_z /(J_x ?+?J_y ))?+?O(1)]^?1) derived earlier by Weng, Griffiths and Fisher (Phys. Rev. 162, 475 (1967)) using an approach that relies on a refinement of the Peierls argument. The constant that was left undetermined in the Weng et al. result is estimated to vary from ～0.84 at ((H_x ?+?H_y )/H_z )?=?10^?2 to ～0.76 at ((H_x ?+?H_y )/H_z )?=?10^?20.