论文标题
Spin-1/2锯齿链中的平频物理
Flat-band physics in the spin-1/2 sawtooth chain
论文作者
论文摘要
我们认为，锯齿链晶格上的强烈各向异性自旋1/2 $ xxz $模型，带有铁磁纵向纵向相互作用$ j^{zz} =Δj$和aniferromagnetic横向互动$ j^{xx} {xx} = j^^{yy} = j^{yy} = j> j> 0 $ 0 $ 0 $ 0 $ 0 $。在$δ= -1/2 $时，最低的一块刺激频段是无散的（平坦），导致一组大量退化的基态。有趣的是，该模型接受了地基歧管的三色表示[H.〜J。〜Changlani et。，Phys。莱特牧师。 {\ bf 120}，117202（2018）]。我们表征了这种基态歧管，并详细阐述了系统的低温热力学。我们通过与两个各向同性扁平型海森贝格锯齿链进行比较来说明各向异性模型的平坦物理学的表现。我们的分析考虑因素与精确的对角和有限的lancos方法计算相辅相成。
We consider the strongly anisotropic spin-1/2 $XXZ$ model on the sawtooth-chain lattice with ferromagnetic longitudinal interaction $J^{zz}=ΔJ$ and aniferromagnetic transversal interaction $J^{xx}=J^{yy}=J>0$. At $Δ=-1/2$ the lowest one-magnon excitation band is dispersionless (flat) leading to a massively degenerate set of ground states. Interestingly, this model admits a three-coloring representation of the ground-state manifold [H.~J.~Changlani et at., Phys. Rev. Lett. {\bf 120}, 117202 (2018)]. We characterize this ground-state manifold and elaborate the low-temperature thermodynamics of the system. We illustrate the manifestation of the flat-band physics of the anisotropic model by comparison with two isotropic flat-band Heisenberg sawtooth chains. Our analytical consideration is complemented by exact diagonalization and finite-temperature Lanczos method calculations.
