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arXiv 2005.10265cond-mat.str-elhep-thquant-ph
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晶格对称阿贝尔拓扑相的晶体规范场和量子化离散几何响应

Crystalline gauge fields and quantized discrete geometric response for Abelian topological phases with lattice symmetry

Naren Manjunath, Maissam Barkeshli

摘要:

在连续介质中,干净的各向同性量子霍尔流体具有许多受保护的量子化不变量,如霍尔电导率、位移和霍尔粘度。在这里,我们开发了一个理论的拓扑相位定义的格,没有连续模拟的量化不变量可以出现的安全保护的量化不变量。我们发展了拓扑场论,使用离散晶体规范场来完全表征具有对称群$G = U(1) \times G_{\text{space}}$的(2+1)D阿贝尔拓扑序的量子化不变量,其中$G_{\text{space}}$由晶格上的保持取向的空间群对称性组成。我们展示了如何离散的旋转和平移对称性分形可以由一个离散的自旋矢量,一个离散的扭转矢量,它没有类似的连续或在没有晶格旋转对称性,和一个面积矢量,它也没有类似的连续。离散的扭转矢量意味着一种晶体动量分馏,它只对$2$、$3$和$4$折叠旋转对称性是非平凡的。量子化拓扑响应理论包括离散版本的移位,其将分数电荷绑定到向错和拐角,分数量子化的向错角动量,旋转对称的分数电荷极化及其角动量对应物,对每单位晶胞的电荷和角动量的约束,以及绑定到位错和面积单位的量子化动量。分数量子化的电荷极化,这是不平凡的,只有在一个晶格与$2$,$3$,和$4$倍旋转对称,意味着一个分数的电荷绑定到晶格位错和分数的电荷沿边界的每单位长度。一个重要的作用是发挥有限群分级伯格斯向量,这取决于点群对称的晶格。

英文摘要:

Clean isotropic quantum Hall fluids in the continuum possess a host of symmetry-protected quantized invariants, such as the Hall conductivity, shift and Hall viscosity. Here we develop a theory of symmetry-protected quantized invariants for topological phases defined on a lattice, where quantized invariants with no continuum analog can arise. We develop topological field theories using discrete crystalline gauge fields to fully characterize quantized invariants of (2+1)D Abelian topological orders with symmetry group $G = U(1) \times G_{\text{space}}$, where $G_{\text{space}}$ consists of orientation-preserving space group symmetries on the lattice. We show how discrete rotational and translational symmetry fractionalization can be characterized by a discrete spin vector, a discrete torsion vector which has no analog in the continuum or in the absence of lattice rotation symmetry, and an area vector, which also has no analog in the continuum. The discrete torsion vector implies a type of crystal momentum fractionalization that is only non-trivial for $2$, $3$, and $4$-fold rotation symmetry. The quantized topological response theory includes a discrete version of the shift, which binds fractional charge to disclinations and corners, a fractionally quantized angular momentum of disclinations, rotationally symmetric fractional charge polarization and its angular momentum counterpart, constraints on charge and angular momentum per unit cell, and quantized momentum bound to dislocations and units of area. The fractionally quantized charge polarization, which is non-trivial only on a lattice with $2$, $3$, and $4$-fold rotation symmetry, implies a fractional charge bound to lattice dislocations and a fractional charge per unit length along the boundary. An important role is played by a finite group grading on Burgers vectors, which depends on the point group symmetry of the lattice.

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