Investigating the Binding of Grains in Ultracold Dusty Plasmas

Steady-state interaction between stationary grains mediated by plasmas at ultracold superfluid helium temperatures is investigated using particle-in-cell (PIC) simulations with Monte-Carlo collisions. A wide-ranging parametric exploration of interdependence of the physical parameters and its consequence on overall grain-plasma dynamics for cryogenic dusty plasmas is presented. Charging of the grains and the density of trapped ions exhibit a remarkable dependence on the particle shape. Grain charging shares a direct relation with ion flow strength as well and manifests contrasting trends at flow strength M
_th
≤ 5 and M
_th
≥ 5. A comparison of an isolated grain electric field and potential with the two-grain-plasma system asserts that the field due to an isolated grain is precisely of the same order as the two grain field at subsonic flows. Binding-energy range is estimated to be 0.16-22 eV at M
_th
= 0-15 and supports the possibility of molecule-like dust structure formation at ultracold temperatures.