We have performed scanning tunneling microscopy and differential tunneling conductance ($dI/dV$) mapping for the surface of the three-dimensional topological insulator ${\mathrm{Bi}}_2{\mathrm{Se}}_3$. The fast Fourier transformation applied to the $dI/dV$ image shows an electron interference pattern near Dirac node despite the general belief that the backscattering is well suppressed in the bulk energy gap region. The comparison of the present experimental result with theoretical surface and bulk band structures shows that the electron interference occurs through the scattering between the surface states near the Dirac node and the bulk continuum states.

• Received 29 December 2010

DOI:https://doi.org/10.1103/PhysRevLett.107.056803