Journal of the Physical Society of Japan
Critical Properties ofS=1Bond-Alternating XXZ Chains and HiddenZ2×Z2Symmetry
Atsuhiro Kitazawa, K. Nomura
Abstract
Critical properties of the spin-1 bond-alternating XXZ chain are studied numerically. This model is appropriate to study the VBS picture and hidden Z 2 × Z 2 symmetry concerning to the Haldane gap problem. The possible phases are the ferromagnetic, the X Y , the Haldane, the dimer, and the Néel ones. The critical properties of this model can be interpreted as the Ashkin-Teller type reflecting the hidden Z 2 × Z 2 symmetry. The phase transitions are of the Berezinskii-Kosterlitz-Thouless type (XY-Haldane and XY-dimer), of the 2D Gaussian type (Haldane-dimer), and of the 2D Ising type (Haldane-Néel and dimer-Néel). We determine the phase boundary and universality class using the recent developed techniques by the authors.