Phase behaviour of a hard sphere colloidal system in the presence of an   external laser field
  We study the phase behaviour of a two-dimensionally confined hard sphere colloidal system in the presence of a periodic light field of two interfering laser beams using Monte Carlo simulations. For a given packing fraction of the particles, the colloidal system undergoes a transition from a modulated liquid to a modulated crystal as the light intensity is increased, corresponding to laser induced freezing. For certain packing fractions of the colloidal particles, the system again becomes a modulated liquid as the field strength crosses a threshold value, showing a re-entrant behaviour. 
Pinaki Chaudhuri, Ajay K. Sood, H. R. Krishnamurthy