  In topological crystalline insulators the topological conducting surface
states are protected by crystal symmetry, in principle making it possible to
pattern nanoscale insulating and conductive motifs solely by breaking local
symmetries on an otherwise homogenous, single-phase material. We show using
scanning tunneling microscopy/spectroscopy that defects that break local
symmetry of SnTe suppress electron tunneling over an energy range as large as
the bulk band gap, an order of magnitude larger than that produced globally via
magnetic fields or uniform structural perturbations. Complementary ab initio
calculations show how local symmetry breaking obstructs topological surface
states as shown by a threefold reduction of the spectral weight of the
topological surface states. The finding highlights the potential benefits of
manipulating the surface morphology to create devices that take advantage of
the unique properties of topological surface states and can operate at
practical temperatures.
