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arXiv 2010.04342cond-mat.quant-gasquant-ph
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光晶格中玻色-爱因斯坦凝聚体的伪时间反转对称性保护拓扑Bogoliubov激发

Pseudo-time-reversal-symmetry-protected topological Bogoliubov excitations of Bose-Einstein condensates in optical lattices

Junsen Wang, Wei Zheng, Youjin Deng

备注：
19 pages, 10 figures
发表信息：
Phys. Rev. A 102, 043323 (2020)
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摘要：

光晶格中玻色-爱因斯坦凝聚体的Bogoliubov激发可能具有类似于AII类费米子中的拓扑绝缘体的能带拓扑。使用的语言的克莱因空间理论，这种拓扑性质被证明是由一个伪的时间反演对称性，是伪反酉和平方$-1$，与相关的散装拓扑不变也是一个$\mathbb Z_2$指数保护。我们构建三个等价的表达式，涉及Pfronan，伪时间反演极化，最实际的，Wannier中心流，所有采用从费米子的情况下，这里定义的伪内积。在存在一个额外的伪酉和伪厄米特反演对称性，一个更简单的表达式。然后，我们研究了两个玩具模型可行的冷原子平台上，以数字确认体边界对应。本文提出的Krein空间方法是研究各种保序拓扑玻色Bogoliubov带的普遍方法。

英文摘要：

Bogoliubov excitations of Bose-Einstein condensates in optical lattices may possess band topology in analogous to topological insulators in class AII of fermions. Using the language of the Krein-space theory, this topological property is shown to be protected by a pseudo-time-reversal symmetry that is pseudo-antiunitary and squares to $-1$, with the associated bulk topological invariant also being a $\mathbb Z_2$ index. We construct three equivalent expressions for it, relating to the Pfaffian, the pseudo-time-reversal polarization, and most practically, the Wannier center flow, all adopted from the fermionic case, defined here with respect to the pseudo inner product. In the presence of an additional pseudo-unitary and pseudo-Hermitian inversion symmetry, a simpler expression is derived. We then study two toy models feasible on cold atom platforms to numerically confirm the bulk-boundary correspondence. The Krein-space approach developed in this work is a universal formalism to study all kinds of symmetry-protected topological bosonic Bogoliubov bands.

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