Emergence, Coalescence, and Topological Properties of Multiple Exceptional Points and Their Experimental Realization

Kun Ding, Guancong Ma, Meng Xiao, Z. Q. Zhang, C. T. Chan*

*Corresponding author for this work

Research output: Contribution to journalJournal articlepeer-review

372 Citations (Scopus)

Abstract

Non-Hermitian systems distinguish themselves from Hermitian systems by exhibiting a phase transition point called an exceptional point (EP), at which two eigenstates coalesce under a system parameter variation. Many interesting EP phenomena, such as level crossings in nuclear and condensed matter physics, and unusual phenomena in optics, such as loss-induced lasing and unidirectional transmission, can be understood by considering a simple 2 × 2 non-Hermitian matrix. At a higher dimension, more complex EP physics not found in two-state systems arises. We consider the emergence and interaction of multiple EPs in a four-state system theoretically and realize the system experimentally using four coupled acoustic cavities with asymmetric losses. We find that multiple EPs can emerge, and as the system parameters vary, these EPs can collide and merge, leading to higher-order singularities and topological characteristics much richer than those seen in two-state systems. The new physics obtained is not limited to the acoustic systems demonstrated here. It also applies to other systems as well, such as coupled photonic cavities and waveguides.

Original languageEnglish
Article number021007
Number of pages13
JournalPhysical Review X
Volume6
Issue number2
DOIs
Publication statusPublished - Apr 2016

Scopus Subject Areas

  • Physics and Astronomy(all)

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