Two-Stage Melting of Paramagnetic Colloidal Crystals in Two Dimensions

Abstract

A novel two-dimensional system of colloidal particles with absolutely calibrated magnetic interaction is used to investigate static and dynamic properties at the 2D crystal to liquid phase transition. We observe two successive transitions from the solid to the liquid phase with an intermediate hexatic phase, in perfect agreement with the theory of Kosterlitz and Thouless. The absolute values of the transition temperatures are given, and we demonstrate that they depend neither on the system size nor on the cooling rate.