一维形变平带哈伯德模型中的铁磁畴壁基态
Ferromagnetic Domain Wall Ground States in One-Dimensional Deformed Flat-Band Hubbard Model
摘要：
在准一维形变平带哈伯德模型中构造了一组精确的具有局域磁畴壁和扩展螺旋结构的基态。在四分之一填充的情况下，我们证明了具有固定磁化强度的基态的唯一性。具有这些结构的基态简并为全自旋上和全自旋下态。这种简并性与XXZ Heisenberg-伊辛模型中的畴壁解相同。我们导出了一个有用的递归关系的畴壁基态的归一化。利用这个递推关系，我们讨论了任意定域算符的基态期望值在无限体积极限下的收敛性。在无限体积系统的基态，平移对称性自发破缺。证明了畴壁基态和激发态的团簇性质。我们还估计了几个观测值的基态期望值的界限，如自旋和电子数密度的一点和两点函数。
英文摘要：
We construct a set of exact ground states with a localized ferromagnetic domain wall and an extended spiral structure in a quasi-one-dimensional deformed flat-band Hubbard model. In the case of quarter filling, we show the uniqueness of the ground state with a fixed magnetization. The ground states with these structures are degenerate with the all-spin-up and all-spin-down states. This property of the degeneracy is the same as the domain wall solutions in the XXZ Heisenberg-Ising model. We derive a useful recursion relation for the normalization of the domain wall ground state. Using this recursion relation, we discuss the convergence of the ground state expectation values of arbitrary local operators in the infinite-volume limit. In the ground state of the infinite-volume system, the translational symmetry is spontaneously broken by this structure. We prove that the cluster property holds for the domain wall ground state and excited states. We also estimate bounds of the ground state expectation values of several observables, such as one- and two-point functions of spin and electron number density.
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