Simultaneous observation of surface- and edge-states of a 2D topological insulator through scanning tunneling spectroscopy and differential conductance imaging
We have grown 2D form of Bi2Se3 through colloidal synthesis method that acts as a topological insulator. We have simultaneously probed surface-states and edge-states of the nanoplates through scanning tunneling spectroscopy (STS). At the interior, density of states (DOS) revealed location of conduction and valence band edges. The DOS at the edges, on the other hand, have brought out gapless conducting states along with a Dirac point at a nonzero value below the Fermi energy representing Dirac cone of a 2D topological insulator. In differential tunnel conductance (dI/dV) images recorded at different voltages, the two sections of the topological insulator could be viewed selectively or simultaneously with a clear contrast in illumination. Upon an increase in the thickness of 2D-nanoplates, the material turned into a 3D topological insulator with gapless surface-states.