论文标题
对称受保护的相互作用的特殊点
Symmetry protected exceptional points of interacting fermions
论文作者
论文摘要
非热量子系统可以表现出被称为特殊点的光谱退化,其中两个或多个特征向量融合,导致了不可用的约旦块。众所周知,对称性可以增强非相互作用系统中的特殊点。在这里,我们研究了这种对称性受保护的特殊点的命运,在存在对称性的情况下,在存在相互作用的情况下,(i)特殊点稳定。他们在参数空间中的传播导致了特征异常的``粉丝''的形成。此外,(ii)我们确定了仅由于相互作用而存在的特殊点的新来源。在非相互作用的情况下,这些点来自可对角的变性。除了它们的创造和稳定性之外,(iii)我们还发现,如果它们在参数空间中与兼容的多体状态相遇,则可以互相歼灭,在端点处形成第三阶特殊点。这些现象是由``异常的扰动理论''从非交互式哈密顿人开始的。
Non-hermitian quantum systems can exhibit spectral degeneracies known as exceptional points, where two or more eigenvectors coalesce, leading to a non-diagonalizable Jordan block. It is known that symmetries can enhance the abundance of exceptional points in non-interacting systems. Here, we investigate the fate of such symmetry protected exceptional points in the presence of a symmetry preserving interaction between fermions and find that, (i) exceptional points are stable in the presence of the interaction. Their propagation through the parameter space leads to the formation of characteristic exceptional ``fans''. In addition, (ii) we identify a new source for exceptional points which are only present due to the interaction. These points emerge from diagonalizable degeneracies in the non-interacting case. Beyond their creation and stability, (iii) we also find that exceptional points can annihilate each other if they meet in parameter space with compatible many-body states forming a third order exceptional point at the endpoint. These phenomena are well captured by an ``exceptional perturbation theory'' starting from a non-interacting Hamiltonian.