论文标题
量子旋转梯子和概括的拓扑挫败感的命运
The fate of topological frustration in quantum spin ladders and generalizations
论文作者
论文摘要
拓扑挫败感(或拓扑机制)是存在经典的零模式,这些模式对许多哈密顿人的扭曲都具有强大的态度。它自然源于系统中的局部性,其相互作用形成了一组约束,例如在几何沮丧的磁铁,球和弹簧中。对于一个经典极限表现出拓扑挫败感的磁铁,一个重要的问题是,当量化自由度的程度时,这种拓扑会发生什么,以及这种挫败感是否会导致物质的异国量子阶段,例如自旋液体。我们为几何沮丧的旋转梯子模型回答这些问题。它具有无限的许多保守量来帮助解决方案的特征。我们发现经典的零模式都通过量子波动来提升,并且该系统具有独特的rung Singlet基态 - 一种琐碎的量子自旋液体。此外,我们发现与已知对称性受保护的拓扑(SPT)接地状态相对应的低能特征状态,以及$ su(2)$对称性的特殊作用,它要求存在经典零模式的额外维度 - 我们称之为对称性富含对称性的拓扑抑制(SETF)的现象。这些结果表明,在几乎SETF制度中对保护法的小小违反可能导致量子疤痕。我们进一步研究了二维双层三角晶格模型,并找到了类似的SETF现象,该现象也导致量子状态下抑制了低能拓扑特征态。这些结果表明,在没有磁性的情况下,经典的拓扑挫败感以有限的自旋表现为渐近低能量模式,并支持外来量子现象。
Topological frustration (or topological mechanics) is the existence of classical zero modes that are robust to many but not all distortions of the Hamiltonian. It arises naturally from locality in systems whose interactions form a set of constraints such as in geometrically frustrated magnets and balls and springs metamaterials. For a magnet whose classical limit exhibits topological frustration, an important question is what happens to this topology when the degrees of freedom are quantized and whether such frustration could lead to exotic quantum phases of matter like a spin liquid. We answer these questions for a geometrically frustrated spin ladder model. It has the feature of having infinitely many conserved quantities that aid the solution. We find classical zero modes all get lifted by quantum fluctuations and the system is left with a unique rung singlet ground state -- a trivial quantum spin liquid. Moreover, we find low-energy eigenstates corresponding to known symmetry protected topological (SPT) ground states, and a special role of $SU(2)$ symmetry, that it demands the existence of extra dimensions of classical zero modes -- the phenomena we call symmetry-enriched topological frustration (SETF). These results suggest small violations of the conservation laws in the nearly SETF regime could lead to quantum scars. We further study a two-dimensional bilayer triangular lattice model and find a similar SETF phenomena which also leads to suppressed low-energy topological eigenstates in the quantum regime. These results suggest that in the absence of magnetic order, classical topological frustration manifests at finite spin as asymptotically low energy modes with support for exotic quantum phenomena.