Staggered-field effect on the one-dimensional quantum antiferromagnet Yb4As3

Inelastic and polarized neutron scattering experiments have been performed to study the one-dimensional (1D) magnetic property in the charge-ordered phase of Yb4As3. In contrast to the magnetic excitation at zero magnetic field explained by the model of spin-1/2 1D Heisenberg antiferromagnet (HAF), a sharp inelastic response and excitation gap at the AF zone center for the 1D Yb-ion chain were observed under the magnetic field perpendicular to the chain. The magnitude of gap obeys a power law function of magnetic field with an exponent of 2/3. The polarized neutron measurement revealed a pronounced increase of field-induced magnetic moment of the Yb ions on the 1D chain below about 10 K under magnetic field perpendicular to the chain, although the magnetic moment under the parallel field is reproduced by the model of spin-1/2 1D HAF. These phenomena under magnetic field are explained well by the theory of the staggered field due to the Dzyaloshinsky-Moriya interaction within the chain. (author)