Phase transitions in two-dimensional model colloids in a one-dimensional external potential

Two-dimensional melting transitions for model colloids in the presence of a one-dimensional external periodic potential are investigated using Monte Carlo simulation and finite size scaling techniques. Here we explore a hard disk system with commensurability ratio p = root 3as/(2d) = 2, where a(s) is the mean distance between the disks and d the period of the external potential. Three phases, the modulate liquid, the locked smectic, and the locked floating solid are observed, in agreement with other experimental and analytical studies. Various statistical quantities like order parameters, their cumulants, and response functions, are used to obtain a phase diagram for the transitions between these three phases.