THE EFFECT OF DISLOCATIONS ON THE ROUGHENING TRANSITION IN THE WEAK-COUPLING APPROXIMATION

The analysis of the roughening transition proposed by Nozieres and Gal let is extended to interfaces threaded with either randomly placed scr ew dislocations or dislocation loops. In both cases we consider a low density of dislocations which intersect normally with the surface lead ing to a local deformation of the crystal planes and to the formation of small steps in the interface. We show that dislocation loops do not change the roughening transition significantly: it still remains with in the Kosterlitz-Thouless universality class of phase transitions. In contrast, randomly placed screw dislocations modify the phase transit ion: the Kosterlitz-Thouless transition is rounded on a length scale o f order the spacing of dislocations. However there is a transition at a slightly lower temperature for randomly placed screw dislocations: t he super-roughening transition. This conclusion is only valid if the d islocations are randomly placed, not if they are distributed as closel y spaced pairs of opposite sign.