Magnetic excitations of spin-1/2 frustrated anisotropic ferromagnetic chain in magnetic field

Onishi, Hiroaki  

We investigate dynamical spin structure factors of a spin-1/2 one-dimensional - XXZ model with competing ferromagnetic and antiferromagnetic in a magnetic field by numerical methods. In a high-field phase, the formation of two-magnon bound states leads to a quadrupole state, the so-called spin nematic state. The longitudinal spin and quadrupole correlations are quasi-long-ranged, while the transverse spin correlation is short-ranged. Regarding the spin dynamics, we can see a difference in dynamical spin structure factors between longitudinal and transverse components: The longitudinal compoment exhibits a gapless mode, while the transverse one shows a gapped mode, since a finite energy is required to break the two-magnon bound state. We will report detailed analyses of the dependence on exchange couplings, anisotropy, and magnetic field. We will discuss possible relevance of the numerical results to real compounds such as LiCuVO.