Two-Triplet-Dimer Excitation Spectra in the Shastry-Sutherland Model for SrCu_2(BO_3)_2

By using the perturbation expansion up to the fifth order, we study the two-triplet-dimer excitation spectra in the Shastry-Sutherland model, where the localized nature of a triplet-dimer, the propagation of a triplet-dimer pair by the correlated hopping and the long-range interactions between triplet-dimers play an essential role. It is found that the dispersion relations for first-neighbor triplet-dimer pair excitations with S=1 and p-type symmetry qualitatively explain the second-lowest branch observed in the neutron inelastic scattering experiment. It is also predicted that the second-lowest branch consists of two components, p_x- and p_y-states, with slightly different excitation energies. The origin of the singlet mode at 3.7meV observed in the Raman scattering experiment is also discussed.Comment: 5 pages, 3 figure

Livestock Producer’s Nutrient Management Planner Guidebook: A Waste Management Planning Guide for Pacific Island Livestock Producers

This Livestock Producer’s Nutrient Management Planner provides you, the livestock producer, with help in developing an animal waste management plan for your farm. The plan will be unique to each individual farm due to differences in the types of animals you raise, where your farm is located, and how you manage your operation. This workbook is designed to provide the basics on laws and regulations, the concept of nutrient flow through your farm, a series of worksheets to establish the status of your operation, and a guide to developing your farm’s nutrient management plan

Exchange interactions and magnetic properties of the layered vanadates CaV2O5, MgV2O5, CaV3O7 and CaV4O9

We have performed ab-initio calculations of exchange couplings in the layered vanadates CaV2O5, MgV2O5, CaV3O7 and CaV4O9. The uniform susceptibility of the Heisenberg model with these exchange couplings is then calculated by quantum Monte Carlo method; it agrees well with the experimental measurements. Based on our results we naturally explain the unusual magnetic properties of these materials, especially the huge difference in spin gap between CaV2O5 and MgV2O5, the unusual long range order in CaV3O7 and the "plaquette resonating valence bond (RVB)" spin gap in CaV4O9

Ab Initio Calculation of Spin Gap Behavior in CaV4O9

Second neighbor dominated exchange coupling in CaV4O9 has been obtained from ab initio density functional (DF) calculations. A DF-based self-consistent atomic deformation model reveals that the nearest neighbor coupling is small due to strong cancellation among the various superexchange processes. Exact diagonalization of the predicted Heisenberg model yields spin-gap behavior in good agreement with experiment. The model is refined by fitting to the experimental susceptibility. The resulting model agrees very well with the experimental susceptibility and triplet dispersion.Comment: 4 pages; 3 ps figures included in text; Revte

The Heisenberg model on the 1/5-depleted square lattice and the CaV4O9 compound

We investigate the ground state structure of the Heisenberg model on the 1/5-depleted square lattice for arbitrary values of the first- and second-neighbor exchange couplings. By using a mean-field Schwinger-boson approach we present a unified description of the rich ground-state diagram, which include the plaquette and dimer resonant-valence-bond phases, an incommensurate phase and other magnetic orders with complex magnetic unit cells. We also discuss some implications of ours results for the experimental realization of this model in the CaV4O9 compound.Comment: 4 pages, Latex, 7 figures included as eps file

Noncoaxial multivortices in the complex sine-Gordon theory on the plane

We construct explicit multivortex solutions for the complex sine-Gordon equation (the Lund-Regge model) in two Euclidean dimensions. Unlike the previously found (coaxial) multivortices, the new solutions comprise $n$ single vortices placed at arbitrary positions (but confined within a finite part of the plane.) All multivortices, including the single vortex, have an infinite number of parameters. We also show that, in contrast to the coaxial complex sine-Gordon multivortices, the axially-symmetric solutions of the Ginzburg-Landau model (the stationary Gross-Pitaevskii equation) {\it do not} belong to a broader family of noncoaxial multivortex configurations.Comment: 40 pages, 7 figures in colou

Quantum magnetism in two dimensions: From semi-classical N\'eel order to magnetic disorder

This is a review of ground-state features of the s=1/2 Heisenberg antiferromagnet on two-dimensional lattices. A central issue is the interplay of lattice topology (e.g. coordination number, non-equivalent nearest-neighbor bonds, geometric frustration) and quantum fluctuations and their impact on possible long-range order. This article presents a unified summary of all 11 two-dimensional uniform Archimedean lattices which include e.g. the square, triangular and kagome lattice. We find that the ground state of the spin-1/2 Heisenberg antiferromagnet is likely to be semi-classically ordered in most cases. However, the interplay of geometric frustration and quantum fluctuations gives rise to a quantum paramagnetic ground state without semi-classical long-range order on two lattices which are precisely those among the 11 uniform Archimedean lattices with a highly degenerate ground state in the classical limit. The first one is the famous kagome lattice where many low-lying singlet excitations are known to arise in the spin gap. The second lattice is called star lattice and has a clear gap to all excitations. Modification of certain bonds leads to quantum phase transitions which are also discussed briefly. Furthermore, we discuss the magnetization process of the Heisenberg antiferromagnet on the 11 Archimedean lattices, focusing on anomalies like plateaus and a magnetization jump just below the saturation field. As an illustration we discuss the two-dimensional Shastry-Sutherland model which is used to describe SrCu2(BO3)2.Comment: This is now the complete 72-page preprint version of the 2004 review article. This version corrects two further typographic errors (three total with respect to the published version), see page 2 for detail

Critical Properties of Condensation of Field-Induced Triplet Quasiparticles

A review on the field-induced magnetic ordering is given, together with some results of a quantum Monte Carlo simulation focused on the critical behevior near the quantum critical point.Comment: Proceedings of SPQS, Sendai, 200

DESIGN OF THE FLAT-TOP ACCELERATION SYSTEM FOR THE JAERI AVF CYCLOTRON

Abstract A flat-top acceleration system for the JAERI AVF cyclotron has been designed. The fifth harmonic of the fundamental frequency is used to obtain uniform energy gain. To determine optimum parameters of the flat-top system, a cold model test was carried out and flat-top waveforms of the voltages were observed successfully in the whole range of the fundamental frequency. An rf power required for generating a flat-top dee voltage of 30 kV was estimated to be about 1 kW. The design of the flat-top cavity is being modified using the MAFIA code