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Observation of Non-Bloch Parity-Time Symmetry and Exceptional Points

Lei Xiao, Tianshu Deng, Kunkun Wang, Zhong Wang, Wei Yi, and Peng Xue
Phys. Rev. Lett. 126, 230402 – Published 10 June 2021
Physics logo See synopsis: An Optical System Defies Conventional Band Theory
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Abstract

Parity-time (PT)-symmetric Hamiltonians have widespread significance in non-Hermitian physics. A PT-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, PT 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 PT-symmetry framework, and reveals the intriguing interplay between PT symmetry and non-Hermitian skin effect.

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  • 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)

Condensed Matter, Materials & Applied PhysicsGeneral PhysicsAtomic, Molecular & Optical

synopsis

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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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Authors & Affiliations

Lei Xiao1,*, Tianshu Deng2,*, Kunkun Wang1, Zhong Wang2,†, Wei Yi3,4,‡, and Peng Xue1,§

  • 1Beijing Computational Science Research Center, Beijing 100084, China
  • 2Institute for Advanced Study, Tsinghua University, Beijing 100084, China
  • 3CAS Key Laboratory of Quantum Information, University of Science and Technology of China, Hefei 230026, China
  • 4CAS Center For Excellence in Quantum Information and Quantum Physics, Hefei 230026, China

  • *These authors contributed equally to this work
  • wangzhongemail@tsinghua.edu.cn
  • wyiz@ustc.edu.cn
  • §gnep.eux@gmail.com

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Issue

Vol. 126, Iss. 23 — 11 June 2021

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