Quantized Decay Charges in Non-Hermitian Networks Characterized by Directed Graphs

作者：Wenwen Liu, Junyao Wu, Li Zhang, Oubo You, Ye Tian, Hongsheng Chen, Bumki Min, Yihao Yang, Shuang Zhang · 发表于：Physical Review Letters · 年份：2025 · DOI：10.1103/dqf4-6fg5 · 被引用次数：1 · 研究领域：Quantum Mechanics and Non-Hermitian Physics、Topological Materials and Phenomena、Nonlinear Photonic Systems

Non-Hermitian physics has unveiled a realm of exotic phenomena absent in Hermitian systems, with the non-Hermitian skin effect (NHSE) showcasing boundary-localized eigenstates driven by non-reciprocal interactions. Here, we introduce a new class of non-Hermitian systems exhibiting pure decay modes-eigenstates with pure, smooth exponential decay, devoid of the oscillatory wave patterns typical of traditional NHSE. Modeled as directed graphs with nonreciprocal hopping, these systems reveal quantized decay charges, defined as the sum of decay constants along edges at each node, offering a novel topological invariant. We derive universal conditions for these modes, enabling versatile configurations from one-dimensional rings, directed graphs with complicated connectivity, to higher-dimensional lattices. Experimental validation using microwave resonant circuits confirms the predicted pure decay profiles. This discovery paves the way for potential applications in photonics, signal processing, and beyond, harnessing the unique topological properties of non-Hermitian networks.