Density Functional Theory of Laser-Induced Freezing in Colloidal Suspensions

We reexamine the density functional theory of laser-induced freezing, i.e., the freezing of a colloidal liquid into crystalline order in the presence of an external periodic modulating potential Vₑ with its wave vectors tuned to the ordering wave vector in the liquid phase. We show definitively that the initial first order freezing transition (at small Vₑ) changes to a continuous one (at large Vₑ) via a tricritical point provided the modulation wave vectors are suitably chosen. We also present predictions for the parameter values of the tricritical points for a realistic colloidal system.