Gang Xu
Institute of Physics, Chinese Academy of Sciences
时间：2014年 9月1日(周一)下午3：00
地点：唐仲英楼A-213
(1)We have generalized the topological classification from insulator to semimetal, and predicted that a novel quantum state with topologically unavoidable band-crossing at Fermi level can be realized in ferromagnetic compound HgCr2Se4. This state is a condensed-matter realization of Weyl fermions in (3+1) D, and should exhibit remarkable features, such as magnetic monopoles, Fermi arcs, as well as QAHE. (2) By combining two topologically trivial ferromagnetic insulators, single-layer Cr-doped (Bi,Sb)2Te3 and GdI2 together, a new band inversion mechanism is occurred between the pz-characterized conduction band from Bi and the dz2 -characterized valence band from Gd, leading to a new 2D Chern insulator with the non-trivial band gap up to 38 meV, in which high temperature quantum anomalous Hall effect can be achieved based on our ab-initio calculations. In addition, we predict that 3D Chern insulator is first realized in (Bi2/3Cr1/3)2Te3 /GdI2 supperlattice.