Experimental Observation of Two-stage Melting in a Two Dimensional Screened Coulomb System

We have observed a two-step melting transition in a two dimensional system with classical screened Coulomb interactions. We have used optical microscopy and digital imaging to investigate the real space and real time behavior of an ultra-clean colloidal suspension of highly charged, submicron sized spheres confined into two dimensions between two smooth glass plates. Colloidal systems are ideal for the study of complex phase transformation behavior in condensed matter as the time and distance scales of the systems are readily experimentally accessible. A videotape of a colloidal system undergoing two dimensional melting will be shown.