Higher harmonics in complex plasmas with alternating screening

We report how higher harmonics of collective excitations emerge in a 2D layer of strongly correlated charged microparticles in a complex plasma with a periodically alternating screening.
The simulation results of the radio frequency discharge and the charged microparticles are obtained using a highly accurate multi-scale and multi-physics approach based on the particle-in-cell technique, Monte Carlo collision calculations, and molecular dynamics simulations.
We also devise a simple phenomenological expression for the dispersion relation of higher harmonics.
Furthermore, our analysis reveals that the periodically alternating screening causes a self-conjugate state with negative refraction.
In doing so, we demonstrate how complex plasmas can serve as a testbed for studying the fundamental physics of a self-conjugate state in strongly correlated systems.