Phase transitions in a confined quasi-two-dimensional colloid suspension

We have used digital video microscopy to study the equilibrium structure of quasi-two-dimensional suspensions of sterically stabilized uncharged polymethylmethacrylate spheres. The spheres are confined between the surfaces of a very thin glass cell. Our experiments reveal the existence of an equilibrium hexatic phase as well as strongly first order liquid-to-hexatic and hexatic-to-solid phase transitions. These observations are in agreement with the predictions of Bladon and Frenkel [Phys. Rev. Lett. 74, 2519 (1995)] for a confined colloid suspension in which the pair interaction potential between particles has a hard core, and either a very short-range attraction or a very short-range step repulsion.