Glass transition in colloidal monolayers controlled by light-induced caging.

We theoretically investigate the glass-transition problem for a quasi-two-dimensional colloidal dense suspension modulated by a one-dimensional periodic external potential as imposed by interfering laser beams. Relying on a mode-coupling approach, we examine the nonequilibrium-state diagram for hard disks as a function of the density and the period of the modulation for various potential strengths. The competition between the local packing and the distortion of the cages induced by the potential leads to a striking nonmonotonic behavior of the glass-transition line, which allows melting of a glass state merely by changing the external fields. In particular, we find regions in the nonequilibrium-state diagram where a moderate periodic modulation stabilizes the liquid state.