Effects of magnetic anisotropy on spin dynamics of ferromagnetic frustrated chain

強磁性フラストレート鎖のスピンダイナミクスにおける磁気異方性の効果

大西 弘明  

Onishi, Hiroaki

By exploiting density-matrix renormalization group techniques, we investigate the spin dynamics of a spin-1/2 one-dimensional - XXZ model with competing ferromagnetic and antiferromagnetic under applied magnetic fields. In a high-field phase, the formation of two-magnon bound states leads to a spin 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. Accordingly, the longitudinal component of the spin excitation has a gapless mode, while the transverse component exhibits a gapped mode. The easy-plane anisotropy disfavors the two-magnon bound state, and in contrast the easy-axis anisotropy stabilizes the two-magnon bound state. We will report detailed analyses of the dependence on exchange coupling parameters and magnetic field, and discuss possible relevance to real compounds such as LiCuVO.