Phase condensation and evaporation: Another look at wave-particle interactions and Landau damping

Phase synchronization is a universal concept in macro- and microstate coupling of complex systems. In this Rapid Communication, we demonstrate the existence of phase synchronization dynamics in a wave-particle interaction process under the framework of a Vlasov-Poisson (VP) system. Starting from a random phase setup, it is shown that the phases of the electrons spontaneously develop coherent patterns in its velocity space. The most interesting finding is that, mediated by the long-wavelength electrostatic mode, the phases of the electrons tend to attract each other, condense into a mean phase, and form a chimera pattern. Due to the finite-time singularity of the mean phase, the phase pattern gets evaporated and recondenses into a different chimera pattern. For the scenario of a finite wavelength, the random phases rapidly condense to slashing lines, which become steeper and steeper through a sequence of evaporation-condensation processes. The slashing pattern drives the mixing of the distribution function in the velocity space, which then induces the damping of the electrostatic mode. This phase self-organization dynamics uncovers another aspect of wave-particle interaction physics, and sheds light onto the longstanding enigma of Landau damping.