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

拓扑绝缘体是最近发现的一种具有金属边缘或表面的绝缘体材料。由于其新颖的性质，拓扑绝缘体越来越受到人们的关注。这些新材料的标志是无隙拓扑表面态（TSS），它受到时间反演对称性的保护，不受非磁扰动的散射。拓扑状态对小的表面扰动的鲁棒性已被实验证明，特别是对于Bi 2Se 3，这是一个简单的三维拓扑绝缘体模型系统。一些理论工作已经预测了打破时间反演对称性的可能性，并在TSS的狄拉克点打开能隙，当磁性原子吸附在Bi2Se3的表面上。然而，在实验方面，理论预测尚未得到满足。磁性原子在Bi_2Se_3上的吸附导致TSS的n型掺杂和表面二维电子气（2DEG）的产生，而在此提议中，表面磁性有序的缺失归因于表面2DEG的存在.因此，建议使用Cu掺杂的Bi2Se3晶体，其中避免了2DEG的产生，作为Bi2Se3的替代物来容纳磁性原子。计划实验研究不同磁性原子的吸附对Cu掺杂Bi2Se3的表面能带结构的影响，特别是对TSS，使用角分辨光电发射光谱。在狄拉克点，在磁原子/Bi2Se3Cux系统的表面处的铁磁相的发展的同义词的间隙开口，是预期的。利用X射线磁性圆二色性技术研究了表面的磁性。最后，上述系统的局部结构和电子特性将使用扫描隧道显微镜进行表征。

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.