Abstract
The band bending (BB) effect on the surface of the second-generation topological insulators implies a serious challenge to design transport devices. The BB is triggered by the effective electric field generated by charged impurities close to the surface and by the inhomogeneous charge distribution of the occupied surface states (SSs). Our self-consistent calculations in the Korringa–Kohn–Rostoker framework showed that in contrast to the bulk bands, the spectrum of the SSs is not bent at the surface. In turn, it is possible to tune the energy level of the Dirac point via the deposited surface dopants. In addition, the electrostatic modifications induced by the charged impurities on the surface induce long range oscillations in the charge density. For dopants located beneath the surface, however, these oscillations become highly suppressed. Our findings are in good agreement with recent experiments, however, our results indicate that the concentration of the surface doping cannot be estimated from the energy shift of the Dirac cone within the scope of the effective continuous model for the protected SSs.
Highlights
The theoretical discovery of the second-generation topological insulators [1] (2GTIs) triggered an intensive experimental effort to observe the predicted surface states [3, 2, 5, 4, 6, 7, 8, 9, 10] (SSs) being protected by time-reversal symmetry [11]
The evolved electrostatic field induces a band bending (BB) in the bulk band structure close to the surface, which was successfully observed by angle-resolved photomeisson (ARPES) experiments as well [3, 2, 4, 18, 17, 14]
That for a Fermi energy located in the bulk band gap the induced excess charge is hosted by the unsaturated SSs
Summary
The theoretical discovery of the second-generation topological insulators [1] (2GTIs) triggered an intensive experimental effort to observe the predicted surface states [3, 2, 5, 4, 6, 7, 8, 9, 10] (SSs) being protected by time-reversal symmetry [11]. An experimental evidence for a large shift of the Dirac cone towards the conduction band was reported by gated terahertz cyclotron resonance measurements performed on thin Bi2Se3 film [19] Besides these comprehensive experimental studies, numerous theoretical works were devoted to the description of the physical properties of the 2GTIs, including first principle calculations [1, 20, 21, 22, 23, 24, 25], tight binding [23, 26, 27] or effective continuous [11] models.
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