Reentrant Transitions in Colloidal or Dusty Plasma Bilayers

Abstract

The phase diagram of crystalline bilayers of particles interacting via a Yukawa potential is calculated for arbitrary screening lengths and particle densities. Staggered rectangular, square, rhombic, and triangular structures are found to be stable including a first-order transition between two different rhombic structures. For varied screening length at fixed density, one of these rhombic phases exhibits both a single and even a double reentrant transition. Our predictions can be verified experimentally in strongly confined charged colloidal suspensions or dusty plasma bilayers.

Electrostatics in soft matter

“…Crystalline bilayers made up of charged particles have been intensively studied these last years in the soft matter colloid community [158,159] as well as in the solid state physics (classical [160,161,162,163,164] and non-classical electrons [165,166,167] ) and dusty plasma communities [168,169]. The effective interaction between these constitutive mesoscopic macroions is neither hard-sphere like nor purely Coulombic, but it is rather described by an intermediate screened Coulomb [also called Yukawa or DLVO (Derjaguin-Landau-Verwey-Overbeek) [170,171]] due to the screening mediated by the additional microions present in the system.…”

“…The equilibrium phase diagram at zero temperature of crystalline bilayers was investigated theoretically in [158]. The constitutive (point-like) particles interact via a Yukawa pair potential of the form…”

Charged colloidal particles in a charged wedge: do they go in or out?

“…Likewise, corresponding theoretical studies on the structure and phase behaviour (see e.g. [13][14][15]) have been performed. Introducing a slight tilt angle between the plate orientation leads to a wedge confining geometry where the local plate-to-plate separation depends on the distance to the wedge cusp.…”

Melting of Colloidal Crystal Films

“…The lack of liquid-solid coexistence in the very thin films stands in contrast to observations from simulation about hard-sphere monolayer and thin-film melting [8,9], perhaps because microgel particles are soft. Melting of monolayers and thin films is known to be sensitive to particle interactions [3,8,24].…”