Fate of fractional quantum Hall states in open quantum systems: Characterization of correlated topological states for the full Liouvillian
Fate of fractional quantum Hall states in open quantum systems: Characterization of correlated topological states for the full Liouvillian
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DOI：
10.1103/physrevresearch.2.033428
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发表时间：
2020-05
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影响因子：
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通讯作者：
Tsuneya Yoshida;Koji Kudo;H. Katsura;Y. Hatsugai
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作者：
Tsuneya Yoshida;Koji Kudo;H. Katsura;Y. Hatsugai
尽管之前对Lindblad方程描述的开放量子系统进行了广泛的分析，但仍不清楚相关的拓扑状态，如分数量子霍尔态，即使在跳跃项存在的情况下也能保持。本文引入了Liouvillian的伪自旋Chern数，它是通过仅对二重Hilbert空间的一个子空间扭曲边界条件来计算的.这样一个拓扑不变量的存在阐明了即使在跳跃项的存在下，拓扑性质保持不变，跳跃项不关闭有效非厄米哈密顿量的差距（通过忽略跳跃项获得）。换句话说，拓扑性质被编码成有效的非厄米哈密顿而不是完整的刘维尔哈密顿。当跳跃项可以写成双希尔伯特空间中的严格块上（下）三角矩阵时，这是特别有用的，在这种情况下，跳跃项的存在或不存在不会影响Liouvillian的谱。利用赝自旋陈氏数，我们研究了具有两体损失但无增益的分数量子霍尔态的特征，阐明了非厄米分数量子霍尔态的拓扑结构即使在跳跃项存在的情况下也是保持不变的.这个数值结果也支持使用非厄米哈密顿显着降低数值成本。类似的拓扑不变量可以被扩展以处理其他空间维度和对称性的相关拓扑状态（例如，具有反转对称性的一维开放量子系统），表明我们的方法具有很高的通用性。
Despite previous extensive analysis of open quantum systems described by the Lindblad equation, it is unclear whether correlated topological states, such as fractional quantum Hall states, are maintained even in the presence of the jump term. In this paper, we introduce the pseudo-spin Chern number of the Liouvillian which is computed by twisting the boundary conditions only for one of the subspaces of the doubled Hilbert space. The existence of such a topological invariant elucidates that the topological properties remain unchanged even in the presence of the jump term which does not close the gap of the effective non-Hermitian Hamiltonian (obtained by neglecting the jump term). In other words, the topological properties are encoded into an effective non-Hermitian Hamiltonian rather than the full Liouvillian. This is particularly useful when the jump term can be written as a strictly block-upper (-lower) triangular matrix in the doubled Hilbert space, in which case the presence or absence of the jump term does not affect the spectrum of the Liouvillian. With the pseudo-spin Chern number, we address the characterization of fractional quantum Hall states with two-body loss but without gain, elucidating that the topology of the non-Hermitian fractional quantum Hall states is preserved even in the presence of the jump term. This numerical result also supports the use of the non-Hermitian Hamiltonian which significantly reduces the numerical cost. Similar topological invariants can be extended to treat correlated topological states for other spatial dimensions and symmetry (e.g., one-dimensional open quantum systems with inversion symmetry), indicating the high versatility of our approach.