DELOCALIZATION OF 2D DIRAC FERMIONS - THE ROLE OF A BROKEN SUPERSYMMETRY

The mechanism of delocalization of two-dimensional Dirac fermions with random mass is investigated, using a superfield representation. Altho ugh localization effects are very strong, one fermion component can de localize due to the spontaneous breaking of a special supersymmetry of the model. The delocalized fermion has a nonsingular density of state s and is described by a diffusion propagator. Supersymmetry is restore d if the mean of the random mass is sufficiently large. This is accomp anied by a critical boson component.