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SUMMARY:From Exceptional Points to Exceptional Bands
DESCRIPTION:Abstract \nExceptional points (EPs) are spectral singularities 
 in non-Hermitian systems\, at which individual eigenvalues and eigenvector
 s become identical. The successful realization of EPs in diverse physical 
 systems\, such as photonics\, acoustics\, cold atoms\, and superconducting
  circuits\, has sparked great interest in fundamental physics and inspired
  a wide range of novel applications. However\, as the term “exceptional
 ” suggests\, EPs are usually isolated spectral points. Consequently\, fu
 nctionalities rooted in EPs face several inherent limitations\, such as na
 rrow bandwidth. Here\, we present a generalization of the concept of EPs c
 haracterized by the coalescence of high-dimensional eigenspaces and overla
 pped spectra. This condition is denoted as “exceptional deficiency.” W
 hen this happens\, two eigenspaces of identical but arbitrarily large dime
 nsions 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. \nThe condition of exceptional deficiency can be reached in a large v
 ariety of systems. We present its realization in a one-dimensional double-
 chain lattice. Intriguingly\, the exceptional deficiency is a route to go 
 beyond the bulk-edge correspondence of non-Hermitian skin effects\, which 
 relates nontrivial point-gap topology to the existence of skin modes. \n 
 Reference\nZhen Li\, Xulong Wang\, Rundong Cai\, Kenji Shimomura\, Congwei
  Lu\, Zhesen Yang\, Masatoshi Sato\, Guancong Ma\, “Exceptional deficien
 cy of non-Hermitian systems\,” Nature Physics (2026). DOI: 10.1038/s4156
 7-026-03259-7\nProf Guancong Ma\nDepartment of Physics\, Hong Kong Baptist
  University\, Kowloon Tong\, Hong Kong\, China \nphgcma@hkbu.edu.hk
URL:https://www.imperial.ac.uk/events/211653/from-exceptional-points-to-exc
 eptional-bands/
DTSTART;TZID=Europe/London:20260811T140000
DTEND;TZID=Europe/London:20260811T160000
LOCATION:B539 - Floor 5 \, Blackett Building\, South Kensington Campus\, Im
 perial College London\, London\, SW7 2AZ\, United Kingdom
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