Field-induced nematic phase in the spin ladder system with easy-axis anisotropy

Sakai, Toru; Tonegawa, Takashi*; Okamoto, Kiyomi*

The spin ladder system with the easy-axis anisotropy in magnetic field is theoretically investigated using the numerically exact diagonalization, the density matrix renormalization group (DMRG) and the finite-size scaling analysis. It is found that the field-induced nematic phase appears above the critical field. In addition, there exists another critical field at which the quantum phase transition from the nematic phase to the conventional field-induced Tomonaga- Luttinger liquid phase occurs. The phase diagram on the coupling anisotropy versus magnetization plane is given by the numerical diagonalization. Furthermore, a typical magnetization curve calculated by the DMRG is presented.