Title: Emergent momentum-space topological pseudospin defects in non-Hermitian systems Show Chinese title

Title: 非厄米系统中出现的动量空间拓扑赝自旋缺陷

Abstract: Topological defects are central to modern physics, from spintronics to photonics, due to their robustness and potential application in information processing. In this work, we discuss topological point defects that spontaneously emerge at the imaginary Fermi arcs (degeneracy lines) in momentum space of two-dimensional systems described by non-Hermitian effective Hamiltonians. In particular, we consider a generic non-Hermitian Dirac model and a phenomenological model describing hybrid light-matter quasiparticles - exciton polaritons hosted in an optical microcavity. In both cases, the eigenenergies of the system have both real and imaginary parts and form two distinct bands corresponding to two (pseudo-)spin states. We describe the trajectories of the point defects characterized by integer-valued topological winding (vorticity) analytically and show that the defects with opposite vorticity annihilate with each other in the fully gapped phases, but are protected from annihilation by the non-Hermitian spectral degeneracies (exceptional and hybrid points) in the gapless phases. We also suggest that the signatures of these defects can be experimentally measured in an exciton-polariton system. Show Chinese abstract

Abstract: 拓扑缺陷在现代物理中至关重要，从自旋电子学到光子学，因为它们具有鲁棒性，并且在信息处理中具有潜在的应用。 在这项工作中，我们讨论了在二维系统动量空间中由非厄米有效哈密顿量描述的虚数费米弧（简并线）上自发出现的拓扑点缺陷。 特别是，我们考虑了一个一般的非厄米狄拉克模型和一个描述混合光-物质准粒子——在光学微腔中宿主的激子极化子的唯象模型。 在两种情况下，系统的本征能量都有实部和虚部，并形成两个对应于两个（伪）自旋态的独立能带。 我们通过解析方法描述了由整数拓扑绕数（涡度）表征的点缺陷的轨迹，并表明在完全禁带相中，具有相反涡度的缺陷会相互湮灭，但在无能隙相中，由于非厄米谱简并（例外点和混合点）的保护，这些缺陷不会被湮灭。 我们还建议，这些缺陷的特征可以在激子极化子系统中进行实验测量。