Abstract
We report how higher harmonics of collective excitations emerge in a two-dimensional 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 multiscale and multiphysics 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 test bed for studying the fundamental physics of a self-conjugate state in strongly correlated systems.