Atomic and electronic structure of the clean and adsorbate covered (0001) surface of the topological insulator Bi2Se3

We review recent progress in the characterization of the atomic and electronic structure of pristine and adsorbate-covered Bi2Se3(0001) using state-of-the-art analysis tools like surface X-ray diffraction, X-ray absorption fine structure, and spin- and momentum-resolved photoemission spectroscopy. On the basis of several examples we show how the topological surface state is modified by structural modifications. One example is the shift of the Dirac point of the pristine Bi2Se3(0001) surface induced by trace amounts of carbon and its concomitant expansion of the topmost inter-layer spacing. Dosing with atomic hydrogen leads to the complete removal of selenium within the top quintuple layer leaving behind a bismuth bilayer on selenium-terminated Bi2Se3(0001) thereby leading to the appearance of hole-like Rashba-split surface states. Gold deposited by molecular beam epitaxy substitutes bismuth within the near surface region involving an opening of a gap in the topological surface state.