Abstract:

I will summarize our recent activity in the molecular beam epitaxy (MBE) growth and characterization of the nontrivial surface states of topological insulator films of Bi_2Te_3 and Bi_2Se_3. We demonstrate the atomically flat morphology and intrinsic topological property of the resulted films by angle resolved photoemission spectroscopy (ARPES) and scanning tunneling microscopy/spectroscopy (STM/STS). By direct imaging standing waves associated with nonmagnetic impurities and steps on Bi_2Te_3 and Bi_2Se_3 (111) surfaces, we show that the topological states have a surface nature and are protected by the time reversal symmetry. The Dirac cone structure is also indicated by the Landau quantization of the topological states in high magnetic field.
 
 
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