Electron interference in the 3D topological insulator Bi$_{2}$Se$_{3}$ probed by scanning tunneling microscope

Three-dimensional topological insulators (TIs) have aroused great attention to the new state of quantum matter originating from the surface state that forms a massless Dirac cone. Among the recently discovered TIs, Bi$_{2}$Se$_{3}$ is regarded as the most promising candidate [1]. However, recent magnetotransport measurements showed that the bulk conductance dominates even in low carrier samples [2], which raises the question of possible scattering channels responsible for the reduced surface mobility. Band structure calculations predict the Dirac point of the surface state to be located close to the bulk valence band maximum [1]. In order to clarify the surface state scattering feature, we have performed differential tunneling conductance mapping for the surface of Bi$_{2}$Se$_{3}$. The fast Fourier transformation image shows an electron interference pattern near the Dirac node, which provides the evidence of near-surface scattering of the spin polarized surface electrons at the Dirac point in Bi$_{2}$Se$_{3}$ into the spin-degenerate bulk continuum states. \\[4pt] [1] Y. Xia et al., Nat. Phys. \textbf{5}, 398 (2009). \\[0pt] [2] N. P. Butch, Phys. Rev. B \textbf{81}, 241301(R) (2010).