Effects of Bond Alternation on the Ground-State Phase Diagram of One-Dimensional XXZ Model

清美 岡本, OKAMOTO, KIYOMI

Guanghua Liu, Wei Li, Wen‐Long You +2 more

F. Soheilian, Mohammad Reza Soltani

Ling Qiang, Guanghua Liu, Guang-Shan Tian

The ground-state properties and quantum phase transitions (QPTs) of the one-dimensional bond-alternative XXZ model are investigated by the infinite time-evolving block decimation (iTEBD) method. The bond-alternative effects on its ground-state phase diagram are discussed in detail. Once the bond alternation is taken into account, the antiferromagnetic phase (Δ > 1) will be destroyed at a given critical point and change into a disordered phase without nonlocal string order. The QPT is shown to be second-order, and the whole phase diagram is provided. For the ferromagnetic phase region (Δ < −1), the critical point r c always equals 1 (independent of Δ), and the QPT for this case is shown to be first-order. The dimerized Heisenberg model is also discussed, and two disordered phases can be distinguished by with or without nonlocal string orders. Both the bipartite entanglement and the fidelity per site, as two kinds of model-independent measures, are capable of describing all the QPTs in such a quantum model.

Kiyoshi Nomura, Tôru Sakai, Masahiro Takahashi

Kazuo Hida

The ground state of the alternating spin-1/2 Heisenberg chain is studied with anisotropy on the antiferromagnetic bond. This model reduces to the spin-1 XXZ chain if the isotropic bond is ferromagnetic and infinitely strong. The ground-state phase diagram is determined by the numerical diagonalization of finite-size systems. The results are consistent with the series expansion results by Yamanaka, Hatsugai and Kohmoto, and confirms the qualitative phase diagram predicted by Kohmoto and Tasaki.