Fig. 3
From: Multiple scattering theory of non-Hermitian sonic second-order topological insulators
Concentric square crystal (CSC) with diagonal non-Hermiticity. a Magnified view of the CSC displaying the arrangement of the trivial and nontrivial regions. b Comparison between the real eigenfrequencies obtained by finite element method simulations (dots) with the normalized pressure of the excited states from the multiple scattering theory computation. c Pressure maps of all corner states. Inserts illustrate the excitation point. d Pressure difference between the amplifying and attenuating upper corner states
