Field induced spin nematic liquid in the 1D anisotropic quantum spin systems

The spin nematic phase is one of interesting topics in the field of the magnetism. The previous theoretical and numerical studies predicted that the spin nematic order would be induced by the frustration of the ferromagnetic and antiferromagnetic exchange interactions, or the biquadratic interaction. The spin nematic order is characterized by the long-range four spin correlation and the two-magnon bound state. The previous numerical diagonalization study had indicated that a similar two-magnon bound state can occur in the S=1 antiferromagnetic chain with the single-ion anisotropy under magnetic field. The recent calculation of the critical exponents of the spin correlation functions suggested that this two-magnon bound state includes the spin nematic liquid phase, as well as the SDW liquid one. Some phase diagrams with respect to the anisotropy and the magnetization were obtained by the numerical diagonalization of finite size clusters. The same numerical analysis indicated that the spin nematic liquid phase appears in the magnetization process of the 1/2 spin ladder system with the anisotropic ferromagnetic rung interaction.