Electronic band structure, magnetic and structural properties of magnetic atoms on Bi2Se3Cux

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Topological Insulators are recently discovered materials characterized essentially by an insulating bulk with metallic edges or surfaces. Thanks to their novel properties, the topological insulators are subject of increasing interest. The hallmark of these new materials is the gapless topological surface state (TSS), which is protected by time-reversal symmetry against scattering from non-magnetic perturbations. The robustness of the topological state against small surface perturbation has been experimentally proven, particularly for Bi2Se3, which is a simple model system of three dimensional topological insulators. Several theoretical works have predicted the possibility to break time-reversal symmetry and open an energy gap at the Dirac point of the TSS, when magnetic atoms are adsorbed on the surface of Bi2Se3. However, on the experimental side, the theoretical predictions have not been satisfied yet. The adsorption of magnetic atoms on Bi2Se3 has rather resulted in an n-doping of the TSS and the creation of a two-dimensional electron gas (2DEG) at the surface.In this proposal, the absence of magnetic ordering at the surface is attributed to the presence of the 2DEG at the surface. Therefore, it is proposed to use the Cu-doped Bi2Se3 crystal, where the creation of the 2DEG is avoided, as an alternative to Bi2Se3 to host the magnetic atoms. It is planned to experimentally investigate the effect of adsorption of different magnetic atoms on the surface band structure of Cu-doped Bi2Se3, and in particular, on the TSS, using angle-resolved-photoemission-spectroscopy. A gap opening at the Dirac point, synonym of a development of a ferromagnetic phase at the surface of the magnetic-atom/Bi2Se3Cux system, is expected. The magnetic properties of the surface will be investigated using X-ray Magnetic Circular Dichroism technique. Finally, the local structural and electronic characteristics of the above system will be characterized using scanning tunneling microscopy.