Generating large complete momentum gaps in temporally modulated dispersive media

This study investigates the generation of a large complete momentum gap (k-gap) in the Lorentzian media with a plasma frequency varying periodically in time. By using the energy expression for the Lorentz model, Maxwell's equations are reformulated as a time-dependent Hamiltonian, allowing an analytical solution of the Floquet band structure. Our simulations reveal a large complete k-gap whose width remains nearly unchanged as the resonance frequency ω0 increases. Numerical analyses further indicate that the k-gap emerges when the modulation frequency Ω approaches the magnitude of unmodulated plasma frequency ωp0. This large k-gap, in contrast to those in previous studies on Floquet systems, suggests potential applications for the developments in non-Hermitian physics or gain mechanisms.