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arXiv 2408.14533cond-mat.str-elcond-mat.mes-hall
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拓扑平带中对称性破缺的阻碍

Obstruction to Broken Symmetries in Topological Flat Bands

Penghao Zhu, Shi Feng, Yuan-Ming Lu

AI总结:

本研究针对二维拓扑平带强关联区的超导与电荷序问题,通过关联三维AIII类拓扑绝缘体表面态,揭示半填充下有能隙对称破缺态的ℤ₈分类拓扑阻碍,并用C=4的哈密顿量验证超导与ℤ₂拓扑序共存。

摘要:

受魔角扭曲双层石墨烯及其他二维材料中大量对称性破缺态的启发,我们研究了强关联区域下二维拓扑平带中的超导(SC)与电荷序。通过将半填充二维拓扑平带与AIII对称类的三维拓扑绝缘体表面态相关联,我们揭示了在半填充时存在反幺正粒子-空穴对称性的情况下,无内禀拓扑序的有能隙超导及谷间电荷序的形成存在拓扑阻碍。这是Li-Haldane关于节点超导的论证向强相互作用电子的推广。与非相互作用能带拓扑导出的ℤ值阻碍不同,半填充平带中相互作用电子的拓扑阻碍具有ℤ₈分类,其取决于超导(谷间电荷)序的电荷(谷)陈数。我们通过一个净陈数C=4的半填充平带相互作用哈密顿量证明了这一点,其中超导与ℤ₂拓扑序在具有粒子-空穴对称性的有能隙基态中共存。

英文摘要:

Motivated by the abundance of symmetry breaking states in magic-angle twisted bilayer graphene and other two-dimensional materials, we study superconducting (SC) and charge orders in two-dimensional topological flat bands in the strong correlation regime. By relating the half-filled 2D topological flat bands to the surface states of 3D topological insulators in symmetry class AIII, we reveal the topological obstruction to the formation of gapped SC and inter-valley charge orders without intrinsic topological orders, in the presence of the anti-unitary particle-hole symmetry at half filling. This is a generalization of the Li-Haldane arguments for nodal superconductivity to strongly interacting electrons. In contrast to the $\mathbb{Z}$-valued obstruction derived from the non-interacting band topology, the topological obstruction of interacting electrons in half-filled flat bands has a $\mathbb{Z}_{8}$ classification, depending on the charge (valley) Chern number of the superconducting (inter-valley charge) orders. This is demonstrated by an interacting Hamiltonian for half-filled flat bands with a net Chern number $C=4$, where superconductivity and $\mathbb{Z}_2$ topological order coexist in a gapped ground state with particle-hole symmetry.

机构、总结、中文摘要均由AI分析而来,可能存在错误,请以论文正文为准。

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