Novel electronic applications often result from fresh theoretical insights into long-familiar materials. Recently, strong interest has focused on the “topological insulators”, notably Bi2Se3and Bi2Te3. In these solids, the electrons on the surface display highly unusual properties. For example, they travel like massless particles (photons and neutrinos), and are much less susceptible to scattering by lattice imperfections. To date, much of the information on topological insulators has come from photoemission experiments and scanning tunneling microscopy. Now a team at Princeton has shown that important information may also be gleaned by isolating the small electrical current carried by the surface electrons. Because of the protection from scattering, the surface electrons execute tight orbits in the presence of a weak magnetic field. The graph is a snapshot of the Hall electric field of the surface electrons versus magnetic field. Both the prominent peaks and the oscillations reflect the high mobility of the surface electrons.
Figure: Trace of the Hall effect of the surface electrons in Bi2Te3versus magnetic field. The large peaks (arrows) reflect the cyclotron orbits of the electrons.