Probing high energy, unoccupied states on the surface of pristine and Fe doped Bi$_{2}$Te$_{3}$ by scanning tunneling spectroscopy

We probe the surface state of pristine and Fe-doped topological Insulator Bi$_{2}$Te$_{3}$ by using Fourier Transform Scanning Tunneling Spectroscopy (FT-STS). FT-STS allows us to probe the surface state dispersion far above the Fermi energy, a regime inaccessible to angle resolved photoemission spectroscopy. We report the observation of novel multi scattering channels that emerge at high energies along the $\Gamma $M and $\Gamma $K directions. The possible origins of these channels including spin-orbit scattering will be discussed.