Vertical probe-induced asymmetric dust oscillation in complex plasma

Spherical, micrometer-sized particles within a Coulomb crystal levitated in the sheath above the powered lower electrode in a GEC reference cell are perturbed using a Zyvex S100 Nanomanipulator. Using the S100, a vertical probe is positioned within the cell at various locations with respect to the crystal formed within the sheath. As the probe is lowered toward the horizontal plane of the dust layer, a circular cavity opens in the center of the crystal and expands. To explore the minimally perturbative state, the probe is lifted to the position that closes this cavity, the probe potential is oscillated, and the motion of the particle directly beneath the probe is analyzed. Using a simple electric field model for the plasma sheath, the change predicted in the levitation height is compared with experiment.