Description
Dusty plasmas provide an ideal platform for studying strongly coupled systems, exhibiting behaviours similar to condensed matter systems. Extensive research has been done using dusty plasma in strongly coupled regimes to understand the collective behaviour, lattice formation, phase transitions, phonon modes, etc. One can use these strongly coupled dusty plasmas to study the collective behaviors of anisotropic solids and nematic liquid crystals. In this study, we investigate the orientational self-organization of charged dimer (charged entities analogous to elongated molecules) clusters in two dimensions, subjected to confining electric fields and periodic boundary conditions (PBCs) using molecular dynamics simulations.
The intrinsic line-body symmetry of dimers greatly alters the formation of lattices as compared to spherical and point particles (monomers), which influences the positional ordering of the dimers. However, to study the orientational ordering, we look at the order parameter S=⟨cos2θ⟩ (with θ as the angle relative to the field), which peaks sharply (for small clusters) when dimers are aligned with the directive field, signaling transitions from isotropic disorder to nematic-like alignment. In larger PBC systems, the nematic tensor captures, Q = 1/N ( u_i.u_i - 1/2 ) global ordering, revealing phase shifts driven by dipole-field coupling and interparticle interactions. These ordering parameters have been studied with respect to the number of dimers, shielding parameter (), and coupling parameter.
These studies show how particle asymmetry governs self-assembly in shaped dusty plasmas, offering insights for designing novel anisotropic/isotropic materials and advancing analogs of liquid crystal physics in confined settings.