Abstract 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 (TLL) 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.
The magnetization process of the S = 1/2 Kondo necklace spin chain with the anisotropic ferromagnetic interaction is investigated using the numerical diagonalization of finite-size systems. As a result, it is found that the two-magnon bound state appears in the field-induced Tomonaga-Luttinger liquid phase for sufficiently large anisotropy. The critical exponent analysis indicates that the spin nematic correlation is dominant at higher magnetization region in the two-magnon bound phase. The phase diagram with respect to the anisotropy and the magnetization is presented.
The magnetization process of the S = 1 antiferromagnetic chain with the single-ion anisotropy D and the biquadratic interaction is investigated using the numerical diagonalization.Both interactions stabilize the 2-magnon Tomonaga-Luttinger liquid (TLL) phase in the magnetization process. Based on several excitation gaps calculated by the numerical diagonalization, some phase diagrams of the magnetization process are presented. These phase diagrams reveal that the spin nematic dominant TLL phase appears at higher magnetizations for sufficiently large negative D.
Abstract The magnetization process of the S = 1 antiferromagnetic chain with the single-ion anisotropy D and the biquadratic interaction is investigated using the numerical diagonalization. Both interactions stabilize the 2-magnon Tomonaga-Luttinger liquid (TLL) phase in the magnetization process. Based on several excitation gaps calculated by the numerical diagonalization, some phase diagrams of the magnetization process are presented. These phase diagrams reveal that the spin nematic dominant TLL phase appears at higher magnetizations for sufficiently large negative D.
We explore the ground-state phase diagram of the
S=1/2 two-leg ladder with different leg interactions. The
xy and
z components of the leg interactions between nearest-neighbor spins in the
a (
b) leg are respectively denoted by
Jl,a and
ΔlJl,a (
Jl,b and
ΔlJl,b). On the other hand, the
xy and
z components of the uniform rung interactions are respectively denoted by
ΓrJr and
Jr. In the above,
Δl and
Γr are the
XXZ-type anisotropy parameters for the leg and rung interactions, respectively. This system has a frustration when
Jl,aJl,b<0 irrespective of the sign of
Jr. The phase diagram on the
Δl (
∣Δl∣≤1.0) versus
Jl,b (
−2.0≤Jl,b≤3.0) plane in the case where
Jl,a=0.2,
Jr=−1.0, and
Γr=0.5 is determined numerically. We employ the physical consideration, and the level spectroscopy and phenomenological renormalization-group analyses of the numerical date obtained by the exact diagonalization method. The resultant phase diagram contains the ferromagnetic, Haldane, N{é}el, nematic Tomonaga-Luttinger liquid (TLL), partial ferrimagnetic, and
XY1 phases. Interestingly enough, the nematic TLL phase appears in the strong-rung unfrustrated region as well as in the strong-rung frustrated one. We perform the first-order perturbational calculations from the strong rung coupling limit to elucidate the characteristic features of the phase diagram. Furthermore, we make the density-matrix renormalization-group calculations for some physical quantities such as the energy gaps, the local magnetization, and the spin correlation functions to supplement the reliability of the phase diagram.