报告题目：Generalization of exceptional points: high-dimensional coalescing non-Hermitian spaces
报告人：马冠聪教授 香港浸会大学
报告时间：2025年11月6日上午10点
报告地点：物科楼405室
报告摘要：Exceptional points (EPs) are spectral singularities in non-Hermitian systems, at which individual eigenvalues and eigenvectors become identical. The successful realization of EPs in diverse physical systems, such as photonics, acoustics, cold atoms, and superconducting cir-cuits, has triggered tremendous interest in fundamental physics and inspired a vast array of novel applications. However, as the term “exceptional” suggests, EPs are usually isolated spectral points. Consequently, functionalities rooted in EPs face several inherent limitations, such as narrow bandwidth. Here, we present a generalization of the concept of EPs character-ized by the coalescence of multi-dimensional Hilbert subspaces and overlapped spectra. This condition is denoted as “exceptional deficiency” (ED). When this happens, two Hilbert sub-spaces of identical but arbitrarily large dimensions exactly align, accompanied by the coinci-dence of their spectra. Consequently, the full Hilbert space is highly defective by “missing” half of its span. In the meantime, the spectrum is entirely composed of EPs.
The condition of ED can be reached in a large variety of systems. We present its reali-zation in a one-dimensional double-chain lattice. Intriguingly, the ED can break the bulk-edge correspondence of non-Hermitian skin effects, which relates nontrivial point-gap topology to the existence of skin modes. As a consequence, we find that the ED underpins new non-Hermitian phenomena characterized by the synergy of skin effects and propagation.
报告人简介：马冠聪，香港浸会大学物理系教授，国家青年科学基金项目(A类)、(B类)获得者。2007年毕业于华南理工大学应用物理学专业本科、2012年获香港科技大学物理学博士学位，之后在香港科技大学高等研究院从事博士后研究，2017年加入香港浸会大学物理系。马教授主要在拓扑物理学和非厄米物理学领域从事研究，在Science、Nature、Nature Materials/Physics、PRL发表论文60余篇，引用9000多次。先后获国际声学会颁发“2021年度青年研究员奖”、中国科协评选为“2021年度十大科技新星”、2022年亚太物理学会协会和亚太理论物理中心颁发“杨振雄奖”。
