Effect of Fluctuations on the Freezing of a Colloidal Suspension in an External Periodic Potential

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We incorporate the effects of fluctuations in a density functional analysis of the freezing of a colloidal liquid in the presence of an external potential generated by interfering laser beams. A mean field treatment, using a density functional theory, predicts that with the increase in the strength of the modulating potential, the freezing transition changes from a first order to a continuous one via a tricritical point for a suitable choice of the modulating wavevectors. We demonstrate here that the continuous nature of the freezing transition at large values of the external potential Vₑ survives the presence of fluctuations. We also show that fluctuations tend to stabilize the liquid phase in the large Vₑ regime.