Fig. 4: Large size systems.

a Dispersion diagrams of the quasienergy spectra as a function of the Floquet period for a system comprising up to N = 50 elements (at κ = 1). The spectral features closely resemble those observed in smaller-sized systems, exhibiting an exceptional point (EP) at T = 2. The real and imaginary parts of the system’s quasienergy spectra are plotted in green and red, respectively. The black dashed lines indicate the Floquet zone boundaries  ±π/T. Maximal order exceptional points are marked by purple dots. The yellow-shaded region denotes the unbroken \({{{\mathscr{PT}}}}\)-symmetric phase of the system. b Amplitudes of Floquet eigenmodes, for different values of the Floquet period. The red dots mark the modal averages of the amplitude at each site. At the exceptional point (T = 2), in all cases, the field localizes fully at the leftmost site, revealing a maximal-order EP.