标题： 非布洛赫狄拉克点和堆叠非厄米SSH模型的相图 显示英文标题

标题： Non-Bloch Dirac Points and Phase Diagram in the Stacked Non-Hermitian SSH Model

摘要： 拓扑半金属在动量空间中表现出受保护的能带交叉，并伴随相应的表面态。 非厄米哈密顿量引入了对几何敏感的特性，从而破坏了这种体-边对应原理。 在本文中，我们通过研究一种具有非互易跃迁和位点增益/损耗的非厄米二维堆叠SSH链模型来说明这一现象。 我们推导了开边界谱中复数能隙的解析相图。 相图揭示了非布洛赫狄拉克点的存在，这些点具有实数谱，并且仅在开边界条件下出现，在周期边界条件下则消失于布洛赫带中。 由于非布洛赫狄拉克点附近谱的实数性，我们可以将其局部映射到Altland-Zirnabuer对称类中的厄米半金属。 基于此映射，我们证明了非布洛赫狄拉克点由整数拓扑电荷表征。 与厄米半金属中的能带交叉不同，不同边界几何下非布洛赫狄拉克点的位置并不匹配，表明非厄米半金属中存在依赖于几何的体-边对应关系。 我们的发现为在非厄米系统中建立非布洛赫狄拉克金属的非常规体-边对应关系提供了新途径。 显示英文摘要

摘要： Topological semimetals exhibit protected band crossings in momentum space, accompanied by corresponding surface states. Non-Hermitian Hamiltonians introduce geometry-sensitive features that dissolve this bulk-boundary correspondence principle. In this paper, we exemplify this phenomenon by investigating a non-Hermitian 2D stacked SSH chain model with non-reciprocal hopping and on-site gain/loss. We derive an analytical phase diagram in terms of the complex energy gaps in the open-boundary spectrum. The phase diagram reveals the existence of non-Bloch Dirac points, which feature a real spectrum and only appear under open boundary conditions but disappear in Bloch bands under periodic boundary conditions. Due to the reality of the spectrum in the vicinity of non-Bloch Dirac points, we can locally map it to Hermitian semimetals within the Altland-Zirnabuer symmetry classes. Based on this mapping, we demonstrate that non-Bloch Dirac points are characterized by an integer topological charge. Unlike the band crossings in Hermitian semimetals, the locations of the non-Bloch Dirac points under different boundary geometries do not match each other, indicating a geometry-dependent bulk-boundary correspondence in non-Hermitian semimetals. Our findings provide new pathways into establishing unconventional bulk-boundary correspondence for non-Bloch Dirac metals in non-Hermitian systems.