Dirac fermions and domain wall defects in 2+1 dimensions

We investigate some properties of a system of Dirac fermions in 2 + 1 dimen sions, with a space-dependent mass having domain wall like defects. These d efects are defined by the loci of the points where the mass changes sign. I n general, they will be curves lying on the spatial plane. We show how to t reat the dynamics of the fermions in such a way that the existence of local ized fermionic zero-modes on the defects is transparent. Moreover, effects due to the higher, no-zero-modes, can be quantitatively studied. We also co nsider the relevance of the profile of the mass near the region where it ch anges sign. Finally, we apply our general results to the calculation of the induced fermionic current, in the linear response approximation, in the pr esence of an external electric field and defects. (C) 1999 Elsevier Science B.V.