Effective spontaneous PT-symmetry breaking in hybridized metamaterials

We show that metamaterials can be used as a testing ground to investigate spontaneous symmetry breaking associated with non-Hermitian quantum systems. By exploring the interplay between near-field dipolar coupling and material absorption or gain, we demonstrate various spontaneous breaking processes of the PT symmetry for a series of effective Hamiltonians associated with the scattering matrix. By tuning the coupling parameter, coherent perfect absorption, laser action, and gain-induced complete reflection (pi reflector) by using an ultrathin metamaterial can be obtained. Moreover, an ideal PT symmetry can be established effectively in a passive system by exploring the balance between scattering and absorption loss using metamaterials.