Effects of Metallic Contacts on Topological Insulator Surface States

We study the effect of the coupling between a time-reversal invariant topological insulator and a metal. The coupling of the surface states to the metal is studied both numerically, using a tight-binding model, and analytically within a two-dimensional effective theory. The original surface state described by a massless Dirac fermion acquires a non-trivial spectral profile upon interaction with the metal. This results in the broadening of the surface modes and a shift in the position of the $\Gamma$- point, which may sink into the valence band at strong coupling.