Bound spinons in an antiferromagnetic S=1/2 chain with a staggered field

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American Physical Society
Inelastic neutron scattering was used to measure the magnetic field dependence of spin excitations in the antiferromagnetic S=1/2 chain CuCl2·2(dimethylsulfoxide) in the presence of uniform and staggered fields. Dispersive bound states emerge from a zero-field two-spinon continuum with different finite energy minima at wave numbers q=π and qi≈π(1-2<Sz>). The ratios of the field dependent excitation energies are in excellent agreement with predictions for breather and soliton solutions to the quantum sine-Gordon model, the proposed low-energy theory for S=1/2 chains in a staggered field. The data are also consistent with the predicted soliton and n=1,2 breather polarizations and scattering cross sections.
staggered field, bound spinons, antiferromagnetic S = 1/2 chain, spin dynamics, solitons, sine-Gordon equation, neutron diffraction, spin excitations, CuCl2·2(dimethylsulfoxide), zero-field two-spinon continuum, molecular magnetism, copper compounds, bound states, antiferromagnetic materials, finite energy minima, breather solutions, soliton solutions, quantum sine-Gordon model
Physical Review Letters 2 July 2004, vol.93, no.1, pp. 017204/1-4