Re-entrant disordering of colloidal molecular crystals on two-dimensional periodicsubstrates

Abstract

Using numerical simulations, we study colloidal ordering and disordering on two-dimensionalperiodic substrates where the number of colloids per substrate minima is two or three. Thecolloids form dimer or trimer states with orientational ordering, referred to as colloidalmolecular crystals. At a fixed temperature such that, in the absence of a substrate, thecolloids are in a triangular floating solid state, upon increasing the substrate strength wefind a transition to an ordered colloidal molecular crystal state, followed by atransition to a disordered state where the colloids still form dimers or trimers but theorientational order is lost. These results are in agreement with recent experiments.