Figure 8.

Lowest frequency edge and corner states for a SSH2D 12 × 12 lattice of silver nanospheres: plot of |p_z|², where p_z is the out-of-plane component of the dipole. The lattice parameters are nanoparticle radius a = 8 nm, unit cell width d = 10a = 80 nm, intracell length t = βd/2 = 1.4 × 5a = 56 nm, and background permittivity ϵ_B = 2.25. Panels (a₁) to (e₁) correspond to the lowest-frequency edge states (see Figure 7) for the different approximations and panels (a₂) to (e₂) correspond to quadrupole corner states.