31 research outputs found
Spatially anisotropic Heisenberg Kagome antiferromagnet
In the search for spin-1/2 kagome antiferromagnets, the mineral volborthite
has recently been the subject of experimental studies [Hiroi et al.,2001]. It
has been suggested that the magnetic properties of this material are described
by a spin-1/2 Heisenberg model on the kagome lattice with spatially anisotropic
exchange couplings. We report on investigations of the Sp(N) symmetric
generalisation of this model in the large N limit. We obtain a detailed
description of the dependence of possible ground states on the anisotropy and
on the spin length S. A fairly rich phase diagram with a ferrimagnetic phase,
incommensurate phases with and without long range order and a decoupled chain
phase emerges.Comment: 6 pages, 6 figures, proceedings of the HFM2006 conference, to appear
in a special issue of J. Phys.: Condens. Matte
Relaxation Dynamics of Photocarriers in One-Dimensional Mott Insulators Coupled to Phonons
We examine recombination processes of photocarriers in one-dimensional Mott
insulators coupled to phonons. Performing density matrix renormalization group
calculations, we find that, even for small electron-phonon coupling, many
phonons are generated dynamically, which cause initial relaxation process after
the irradiation. At the same time, spin-charge coupling coming from mixing of
high- and low-energy states by the irradiation is suppressed. We discuss
differences between Mott and band insulators in terms of relaxation dynamics.Comment: 5 pages, 3 figure
Nonequilibrium Current in the One Dimensional Hubbard Model at Half-Filling
Nonlinear transport in the one dimensional Hubbard model at half-filling
under a finite bias voltage is investigated by the adaptive time-dependent
density matrix renormalization group method. For repulsive on-site interaction,
dielectric breakdown of the Mott insulating ground state to a current-carrying
nonequilibrium steady state is clearly observed when the voltage exceeds the
charge gap. It is found that by increasing the voltage further the
current-voltage characteristics are scaled only by the charge gap and the
scaling curve exhibits almost linear dependence on the voltage whose slope is
suppressed by the electron correlation. In the case of attractive interaction
the linear conductance is the perfect one which agrees with the
prediction by the Luttinger liquid theory.Comment: 4 pages, 7 figure
Reconstruction of non-uniformly sampled five-dimensional NMR spectra by signal separation algorithm
WCTE 2016 - World Conference on Timber Engineering
In this paper a novel and efficient structural system, that comprises steel beams and prefabricated timber slabs is developed and tested under short-term service and ultimate limit state loading conditions. In the proposed steeltimber composite (STC) system, bolt and coach screws are employed to transfer shear between steel beam and prefabricated timber slab and provide a composite connection. A series of experimental push-out tests were carried out on cross-banded LVL-Steel and CLT-Steel hybrid specimens to investigate the behaviour of different connection types. Furthermore, the load-deflection response of full-scale STC beams was captured by conducting 4-point bending tests on STC beams. The failure modes of connections and composite beams have been monitored and reported. The results illustrate advantages of using timber panels in conjunction with steel girders in terms of increasing strength and stiffness of composite beams