Melting of Crystals in Two Dimensions

While the melting of crystals is in general not understood in detail on a microscopic scale, there is a microscopic theory for a class of two-dimensional crystals, which is based on the formation and unbinding of topological defects. Herein, we review experimental work on a colloidal two-dimensional model system with tunable interactions that has given the first conclusive evidence for the validity of this theory on a microscopic level. Furthermore, we show how the mechanism of melting depends on the particle interaction and that a strong anisotropy of the interaction leads to a changed melting scenario.