  The electron scattering from periodic line defects on the surface of
topological insulators with hexagonal warping effect is investigated
theoretically by means of a transfer matrix method. The influence of surface
line defects, acting as structural ripples on propagation of electrons are
studied in two perpendicular directions due to the asymmetry of warped energy
contour under momentum exchange. The transmission profiles and the details of
resonant peaks which vary with the number of defects and the strength of their
potentials are strongly dependent on the direction in which the line defects
extend. At low energies, the quantum interference between the incident and
reflected propagating electrons has the dominant contribution in transmission
resonances, while at high energies the multiple scattering processes on the
constant-energy contour also appear because of the strong warping effect. By
increasing the spatial separation between the line defects, the minimum value
of electrical conductance remains significantly high at low incident energies,
while the minimum value may approach zero at high energies as the number of
defects is increased. Our findings suggest that the potential ripples on the
surface of topological insulators can be utilized to control the local
electronic properties of these materials.
