10,923 research outputs found
Electron Spin Resonance of defects in the Haldane System Y(2)BaNiO(5)
We calculate the electron paramagnetic resonance (EPR) spectra of the
antiferromagnetic spin-1 chain compound Y(2)BaNi(1-x)Mg(x)O(5) for different
values of x and temperature T much lower than the Haldane gap (~100K). The
low-energy spectrum of an anisotropic Heisenberg Hamiltonian, with all
parameters determined from experiment, has been solved using DMRG. The observed
EPR spectra are quantitatively reproduced by this model. The presence of
end-chain S=1/2 states is clearly observed as the main peak in the spectrum and
the remaining structure is completely understood.Comment: 5 pages, 4 figures include
The S=1/2 chain in a staggered field: High-energy bound-spinon state and the effects of a discrete lattice
We report an experimental and theoretical study of the antiferromagnetic
S=1/2 chain subject to uniform and staggered fields. Using inelastic neutron
scattering, we observe a novel bound-spinon state at high energies in the
linear chain compound CuCl2 * 2((CD3)2SO). The excitation is explained with a
mean-field theory of interacting S=1/2 fermions and arises from the opening of
a gap at the Fermi surface due to confining spinon interactions. The mean-field
model also describes the wave-vector dependence of the bound-spinon states,
particularly in regions where effects of the discrete lattice are important. We
calculate the dynamic structure factor using exact diagonalization of finite
length chains, obtaining excellent agreement with the experiments.Comment: 16 pages, 7 figures, accepted by Phys. Rev.
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