The effect of the spin-orbit and Coulomb interactions on the symmetry and topological properties of the s, p, d, and s + d phases of an excitonic insulator has been considered by example of the inverted two-band structure of the HgTe quantum well. It has been found that only the p phase has a nontrivial topology, but it is metastable. It has been shown that the exchange interaction between fermions induces the ground state with the s + d symmetry of the excitonic order parameter. This phase of the excitonic insulator has zero Chern number; nevertheless, edge states occur in the case of open boundaries.

中文翻译：

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具有自旋-轨道相互作用的激子绝缘子的边缘状态

自旋轨道和库仑相互作用对激子绝缘子的s，p，d和s + d相的对称性和拓扑性质的影响已通过HgTe量子阱的反向两波段结构实例进行了研究。已经发现只有p相具有非平凡的拓扑，但是它是亚稳的。已经表明，费米子之间的交换相互作用以激子有序参数的s + d对称性诱导基态。激子绝缘子的这一阶段的Chern数为零；但是，在开放边界的情况下会发生边缘状态。