Engineered Near-Perfect Back-Scattering on Surface of Topological   Insulator with Non-Magnetic Impurities
  We show how to engineer enhanced skew scattering and gap-like opening in the surface state of three-dimensional topological insulators using only non-magnetic impurities. Enhanced skew scattering off non-magnetic impurities is obtained as a finite size effect of the scattering potential. Intimately related to the generated skew-scattering is the emergence of a gap-like density of electron states locally around the impurities and surrounded by sharp resonances, with an extended energy gap appearing in engineered impurity structures. 
J. Fransson and A. M. Black-Schaffer and A. V. Balatsky
cond-mat.mes-hall cond-mat.mtrl-sci