First Order Transitions Between the Gapped Spin-Liquid and Ferrimagnetic Phases in (1/2,1/2,1) Mixed Diamond Chains with Bond Alternation
| Autor: | Kazuo Hida |
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| Rok vydání: | 2021 |
| Předmět: | |
| DOI: | 10.48550/arxiv.2111.07054 |
| Popis: | The ground-state phases of mixed diamond chains with bond alternation $\delta$, and ($S, \tau^{(1)}, \tau^{(2)})=(1/2,1/2,1)$, where $S$ is the magnitude of vertex spins, and $\tau^{(1)}$ and $\tau^{(2)}$ are those of apical spins, are investigated. The two apical spins in each unit cell are connected by an exchange coupling $\lambda$. The exchange couplings between the apical spins and the vertex spins take the values $1+\delta$ and $1-\delta$ alternatingly. This model has an infinite number of local conservation laws. For large $\lambda$ and $\delta \neq 0$, the ground state is equivalent to that of the spin $1/2$ chain with bond alternation. Hence, the ground state is a gapped spin liquid. This energy gap vanishes for $\delta=0$. With the decrease of $\lambda$, the ground state undergoes a transition at $\lambda=\lambda_{\rm c0}(\delta)$ to a series of ferrimagnetic phases with a spontaneous magnetization $m_{\rm sp}=1/p$ per unit cell where $p$ is a positive integer. It is found that this transition is a first order transition for $\delta\neq 0$ with a discontinuous change in $m_{\rm sp}$, while no discontinuity is found for $\delta=0$. The critical behaviors of $m_{\rm sp}$ and $\lambda_{\rm c0}(\delta)$ around the critical point $(\delta,\lambda) =(0, \lambda_{\rm c0}(\delta))$ are also discussed analytically. Comment: 5 pages, 5 figures. Several mistakes in equations are corrected. Work closely related to arXiv:2102.02116(=J. Phys. Soc. Jpn. 90, 054701 (2021)) |
| Databáze: | OpenAIRE |
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