Rotating particle pair produces hot complex plasma crystals.

Abstract

Rotating quasipaired particles (torsions) are observed within a two-dimensional monolayer crystal suspended in an argon complex plasma for discharge powers of 1-10 W and pressures of 135-155 mTorr. The inclusion of a torsion in a crystal lattice fundamentally changes the overall lattice state to a "hot crystal." A torsion increases the particle motion and kinetic energy of other particles in the crystal, with the strongest effects on neighboring particles. The apparent effective range is to the third nearest neighbor, with the kinetic energy in the first three shells of particles increasing by at least 200% over baseline values for the crystal. However, the variance of the motion of all particles in the crystal increases by more than two times over the average background kinetic fluctuations for the whole crystal. The formation of a torsion perturbs the structure and symmetry of a plasma crystal. A single torsion causes the average interparticle spacing to increase by 11% compared to the same crystal without a torsion. Particles in the first two shells surrounding a torsion also display reduced hexagonal symmetry. The combination of the perturbed lattice structure and the larger range of motion for the microparticles contribute to a higher-energy-state crystal when torsions are present.