Band bending at the surface of Bi2Se3 studied from first principles

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. OPEN ACCESS RECEIVED

Electronic Structure and X-Ray Magnetic Circular Dichroism in Sm-Doped Bi2Se3

“…2c) two chiral surface states are clearly seen to connect the conduction band and valence band to form a single Dirac-type contact at the Γ point and aligning with the Fermi energy. Our calculations are in good agreement with previous calculations [18,19]. shows the calculated XAS spectra in the GGA approximation together with the experimental spectra measured by Chen et al [6].…”

Band Structure of Topological Insulator BiSbTe1.25Se1.75

“…Further experiments were performed to understand the BB effect by using a laboratory HeI (21.2 eV) photon source in combination with a Scienta R3000 electron energy analyzer. It has earlier been proposed that the BB in TIs originate from accumulation of additional charges at the surface and these extra charges arise due to Se vacancies present in the bulk as well as those created at the surface in the process of surface cleaving 30 , 31 . Moreover, adsorption of residual gases further changes the charge distribution at the surface 10 – 12 .…”

Complex band structure of topological insulator Bi2Se3

“…This seems to be particularly important in the case of Bi 2 Se 3 where the position of the Dirac point with respect to the Fermi energy is particularly sensitive to the interface properties. This is exemplified by the 'ageing effect' in Bi 2 Se 3 which is the downshift of the Dirac point with time after surface cleavage due to adsorption of atoms on the surface [28,29,30]. Thus, detailed studies of the interfaces of the TI with other materials, in particular ferromagnetic metals, is complementary to the studies of the CBS for the purpose of understanding the transport properties of TI-based devices [31].…”