Roughening transition of interfaces in disordered systems

The behavior of interfaces in the presence of both lattice pinning and random field (RF) or random bond (RB) disorder is studied using scaling arguments and functional renormalization techniques. For the first time we show that there is a continuous disorder driven roughening transition from a flat to a rough state for internal interface dimensions 2 < D < 4. The critical exponents are calculated in an epsilon expansion. At the transition the interface shows a superuniversal logarithmic roughness for both RF and RE systems. A transition does not exist at the upper critical dimension D-c = 4. The transition is expected to be observable in systems with dipolar interactions by tuning the temperature.