Experimental Study of Laser-Induced Melting in Two-Dimensional Colloids

We study the phase behavior of a charged two-dimensional colloidal system in the presence of a periodic light field composed of two interfering laser beams. Above a certain light intensity, the light field initiates a liquid-solid transition. This effect is known as light-induced freezing. When the light field is increased above a critical value, however, the induced crystal is predicted to melt into a modulated liquid again. In this paper we report the first direct experimental observation of this reentrance phenomenon.