主讲人：马冠聪，香港浸会大学教授
时 间：2025年12月24日10:30
地 点：物电学院A栋334
联系人: 郭清华
Abstract: 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 circuits, 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 characterized 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 coincidence 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 realization 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.
主讲人简介：马冠聪博士现于香港浸会大学物理系任职教授。他于2007年本科毕业于华南理工大学应用物理系，2007至2012年于香港科技大学物理系就读并取得物理学博士学位。2012-2017年分别在香港科技大学物理系和高等研究院任博士后研究员。现任香港物理学会理事会成员。2021年获评“十大科技新锐人物”，同年获国际声子学协会（International Phononics Society）颁发“青年研究者奖”。2022年获亚太物理学会联合会与亚太理论物理中心联合颁发的“杨振宁奖”，为首位获此殊荣的香港学者。多次入选科睿唯安“全球前2%科学家”。获得国家高层次人才计划-青年科学基金项目（A类）资助。马博士的研究兴趣主要集中于人工体系中的拓扑物理、非厄米物理以及声波超材料等。以通讯作者在Science、Nature、Nature Physics 、Nature Photonics、Physical Review Letters等期刊发表论文60余篇。科研成果共获8项美国发明专利授权，9项中国发明专利授权，部分专利在香港特别行政区成功实现转化。现担任Science Bulletin特邀编委，并获该期刊评选为2021年度最佳审稿人、2024年度最佳编委。
