Nonreciprocal coupling in space-time modulated systems at exceptional points

Exceptional points (EPs) are critical points in the parameter space of non-Hermitian systems, where two or more eigenvalues and eigenvectors simultaneously coalesce. The remarkable physics and behavior of waves at these EPs have raised considerable attention. Previous research has accessed EPs in parity-time (PT) symmetric systems through spatially modulated parameters. Using acoustics, this Letter demonstrates a different family of EPs in classical wave systems that emerge from coordinated modulation of mass density and loss/gain in time. This condition can create nonreciprocal coupling between arbitrary modes at the EPs, leading to exotic behaviors such as unilateral frequency conversion and linear amplification of waves that are unattainable at conventional time-invariant systems. Moreover, these phenomena can be attained with only loss, and acoustic gain via modal energy transfer is demonstrated in a loss-only system at such EPs. Our work marries time-varying systems with EPs, which could open new avenues for wave manipulation.



Work Title Nonreciprocal coupling in space-time modulated systems at exceptional points
Open Access
  1. Junfei Li
  2. Yun Jing
  3. Steven A. Cummer
License In Copyright (Rights Reserved)
Work Type Article
  1. Physical Review B
Publication Date March 28, 2022
Publisher Identifier (DOI)
Deposited July 19, 2022




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Work History

Version 1

  • Created
  • Added PhysRevB.105.L100304.pdf
  • Added Creator Junfei Li
  • Added Creator Yun Jing
  • Added Creator Steven A. Cummer
  • Published
  • Updated Publisher, Publication Date Show Changes
    • Physical Review B-Condensed Matter
    • Physical Review B
    Publication Date
    • 2022-03-01
    • 2022-03-28
  • Updated