Splitting of fluid layers in a modulated colloidal fluid film

Abstract Colloidal fluids subject to external modulations show non-trivial extended structures. Here, we study by computer simulations and a phenomenological Landau theory, a two-dimensional colloidal system modulated in one direction by a spatially periodic external potential with a modulation wavelength twice the mean inter-particle separation. The density profile for low modulation strength shows splitting of the fluid layers about the minimum of the external modulation. On the other hand, for large strength, the modulated fluid density profile shows a peak at the minimum of the external potential. The order parameter for the transition from a split fluid layer to a modulated fluid layer changes continuously, while the specific heat shows discontinuity. Our Landau theory shows that the structural changes take place via a continuous phase transition. Our work shows that the modulated colloidal system may act as a colloidal template for designing an array of micrometer-sized channels.