  The response of a two-dimensional plasma crystal to an externally imposed
initial perturbation has been explored using molecular dynamics (MD)
simulations. A two-dimensional (2D) monolayer of micron-sized charged particles
(dust) is formed in the plasma environment under certain conditions. The
particles interacting via Yukawa pair potential are confined in the vertical
($\hat z$) direction by an external parabolic confinement potential, which
mimics the combined effect of gravity and the sheath electric field typically
present in laboratory dusty plasma experiments. An external perturbation is
introduced in the medium by displacing a small central region of particles in
the vertical direction. The displaced particles start to oscillate in the
vertical direction, and their dynamics get modulated through a parametric decay
process. Consequently, beats generate in the vertical motion of the particles.
It has also been shown that the same motion is excited in the dynamics of
unperturbed particles as they are coupled via pair interactions. A simple
theoretical model is provided to understand the origin of the beat motions of
particles. Additionally, in our simulations, concentric circular wavefronts
propagating radially outward are observed on the surface of the monolayer. The
physical mechanism and parametric dependence of the observed phenomena are
discussed in detail. It has been shown that the generated surface wave follows
the dispersion relation of a transverse shear wave. This research provides
insight into complex plasma crystals from the perspective of soft matter.
