Clock-symmetric non-Hermitian second-order topological insulator

We consider a breathing Kagome lattice with complex hoppings by imposing $$ \mathbb {Z}_{3}$$ clock symmetry in the complex-energy plane. It is non-Hermitian generalization of second-order topological insulator characterized emergence corner states. construct states $$\mathbb clock-symmetric model. also shown that model realized an electric circuit properly designed, where are observed impedance resonance. {Z}_{4}$$ and {Z}_{6}$$ symmetric models on square honeycomb lattices, respectively.