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Crossover of Three-Dimensional Topological Insulator of Bi2Se3 to the Two-Dimensional Limit

Crossover of Three-Dimensional Topological Insulator of Bi2Se3 to the Two-Dimensional Limit. By Qi -Kun Xue’s group, http ://arxiv.org/abs/0911.3706. TI study group Helin Cao 2010/7/7. ARPES technique. 50 quintuple layer Bi2Se3 films. RHEED pattern STM image ARPES spectra

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Crossover of Three-Dimensional Topological Insulator of Bi2Se3 to the Two-Dimensional Limit

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  1. Crossover of Three-Dimensional Topological Insulator of Bi2Se3 to the Two-Dimensional Limit By Qi-Kun Xue’s group, http://arxiv.org/abs/0911.3706 TI study group Helin Cao 2010/7/7

  2. ARPES technique

  3. 50 quintuple layer Bi2Se3 films RHEED pattern STM image ARPES spectra Thickness-dependentphotoemission spectra

  4. Crossover from 3D to 2D nearly parabolic band dispersion the band moves down by 40 meV and another band appears. the gap decreases. the upper surface states are split into two branches (Rashba-type splitting) the gap decreases further. the gap disappears. The inner branches of the upper surface states connect the lower surface states, resulting in a Dirac cone.

  5. ARPES data analyses

  6. Rashba splitting To model the substrate effect, we invoke an effective electrical potential V(z) along the film normal direction. Bernevig-Hughes-Zhang (BHZ) model of the 2D QSH insulator The two Dirac cones obtained from Eq. (2) correspond to the two sets of gapless surface states from the surface and interface sides of the film, respectively. Short message: Rashba splitting can be controlled by modifying band bending, which can be easily realized by applying a gate voltage. Good for spintronics.

  7. summery • Thickness-dependent ARPES study reveals gap-opening and Rashba spin-orbit splitting in the topologically protected surface states. It results from the coupling between the surface states from the opposite surfaces with different chemical potentials. The existence of gapless surface states at interface side of a TI provides an evidence for the robustness of topological states.

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