S=½ chain in a staggered field: high-energy bound-spinon state and the effects of a discrete lattice

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American Physical Society
We report an experimental and theoretical study of the antiferromagnetic S=½ chain subject to uniform and staggered fields. Using inelastic neutron scattering, we observe a 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=½ 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.
discrete lattice, staggered field, bound-spinon state, spin dynamics, fermion systems, Heisenberg model, neutron scattering, linear chain compound, mean-field theory, spinon interactions, Fermi surface, copper compounds, chlorine compounds, antiferromagnetic materials, wave-vector, dynamic structure factor, exact diagonalization, finite length chain
Physical Review B (Condensed Matter and Materials Physics) 1 March 2005, vol.71, no.9, pp. 94411-1-8