4,096 research outputs found

    Field induced long-range-ordering in an S=1 quasi-one-dimensional Heisenberg antiferromagnet

    Full text link
    We have measured the heat capacity and magnetization of the spin one one-dimensional Heisenberg antiferromagnet NDMAP and constructed a magnetic field versus temperature phase diagram. We found a field induced long-range magnetic ordering. We have been successful in explaining the phase diagram theoretically.Comment: 6 pages, 18 figure

    Self-trapped bidirectional waveguides in a saturable photorefractive medium

    Full text link
    We introduce a time-dependent model for the generation of joint solitary waveguides by counter-propagating light beams in a photorefractive crystal. Depending on initial conditions, beams form stable steady-state structures or display periodic and irregular temporal dynamics. The steady-state solutions are non-uniform in the direction of propagation and represent a general class of self-trapped waveguides, including counterpropagating spatial vector solitons as a particular case.Comment: 4 pages, 5 figure

    A new type of solution of the Schr\"odinger equation on a self-similar fractal potential

    Full text link
    Scattering a quantum particle by a self-similar fractal potential on a Cantor set is investigated. We present a new type of solution of the functional equation for the transfer matrix of this potential, which was derived earlier from the Schr\"odinger equation.Comment: Latex, 4 pages, 7 eps-figures; the old figures are renewed and new ones are adde

    Field-induced 3- and 2-dimensional freezing in a quantum spin liquid

    Full text link
    Field-induced commensurate transverse magnetic ordering is observed in the Haldane-gap compound \nd by means of neutron diffraction. Depending on the direction of applied field, the high-field phase is shown to be either a 3-dimensional ordered N\'{e}el state or a short-range ordered state with dominant 2-dimensional spin correlations. The structure of the high-field phase is determined, and properties of the observed quantum phase transition are discussed.Comment: 4 pages 3 figure

    Spin-Reorientation Transition of Field-Induced Magnetic Ordering Phases in the Anisotropic Haldane System

    Full text link
    A possible spin-reorientation transition in field-induced magnetic ordering phases of the S=1 Haldane system with large easy-plane anisotropy is proposed, using an effective Lagrangian formalism as well as the density matrix renormalization group method. Such a spin-reorientation transition is predicted in the case where the applied magnetic field is inclined from the easy axis of the anisotropy. We point out that this transition has a close connection with a variation of the order parameter even at zero temperature, although it is different from a quantum analog of the so-called spin-flop transition proposed for the system having a strong easy axis anisotropy. In connection with a novel phase observed recently in the Haldane system at high fields, we discuss possible implications for the field-induced magnetic ordering.Comment: 14 pages, 7 figure

    Massive triplet excitations in a magnetized anisotropic Haldane spin chain

    Full text link
    Inelastic neutron scattering experiments on the Haldane-gap quantum antiferromagnet \nd are performed at mK temperatures in magnetic fields of almost twice the critical field HcH_c applied perpendicular to the spin cahins. Above HcH_c a re-opening of the spin gap is clearly observed. In the high-field N\'eel-ordered state the spectrum is dominated by three distinct long-lived excitation branches. Several field-theoretical models are tested in a quantitative comparison with the experimental data.Comment: 4 pages, 3 figure

    On the classification of tight contact structures II

    Get PDF
    Abstract We present complete classification results for tight contact structures on two classes of 3-manifolds: (i) torus bundles which fiber over the circle and (ii) circle bundles which fiber over closed surfaces

    Quasi-elastic neutron scattering in the high-field phase of a Haldane antiferromagnet

    Full text link
    Inelastic neutron scattering experiments on the Haldane-gap quantum antiferromagnet NDMAP are performed in magnetic fields below and above the critical field Hc at which the gap closes. Quasi-elastic neutron scattering is found for H>Hc indicating topological excitations in the high field phase.Comment: Added to discussion section. v2: Updated figure

    Critical phase of a magnetic hard hexagon model on triangular lattice

    Full text link
    We introduce a magnetic hard hexagon model with two-body restrictions for configurations of hard hexagons and investigate its critical behavior by using Monte Carlo simulations and a finite size scaling method for discreate values of activity. It turns out that the restrictions bring about a critical phase which the usual hard hexagon model does not have. An upper and a lower critical value of the discrete activity for the critical phase of the newly proposed model are estimated as 4 and 6, respectively.Comment: 11 pages, 8 Postscript figures, uses revtex.st
    • …
    corecore