Abstract
Parity-time ()-symmetric Hamiltonians have widespread significance in non-Hermitian physics. A -symmetric Hamiltonian can exhibit distinct phases with either real or complex eigenspectrum, while the transition points in between, the so-called exceptional points, give rise to a host of critical behaviors that holds great promise for applications. For spatially periodic non-Hermitian systems, symmetries are commonly characterized and observed in line with the Bloch band theory, with exceptional points dwelling in the Brillouin zone. Here, in nonunitary quantum walks of single photons, we uncover a novel family of exceptional points beyond this common wisdom. These “non-Bloch exceptional points” originate from the accumulation of bulk eigenstates near boundaries, known as the non-Hermitian skin effect, and inhabit a generalized Brillouin zone. Our finding opens the avenue toward a generalized -symmetry framework, and reveals the intriguing interplay between symmetry and non-Hermitian skin effect.
- Received 13 January 2021
- Accepted 29 April 2021
DOI:https://doi.org/10.1103/PhysRevLett.126.230402
© 2021 American Physical Society
Physics Subject Headings (PhySH)
synopsis
An Optical System Defies Conventional Band Theory
Published 10 June 2021
Squeezed wave functions reshape an open quantum system’s bulk-boundary properties and generate a new class of parity-time symmetry.
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