The interplay of the topology of electronic wavefunctions with spin configurations in intrinsically magnetic topological insulators (TIs) causes various exotic topological states, which attracts much attention in condensed matter physics. In this work, we study the magnetic and electronic properties and edge states of two-dimensional CoBi2Te4. Based on our density functional theory and tight-binding calculations, CoBi2Te4 films are predicted to present intrinsic intralayer non-collinear antiferromagnetism (ncAFM). The large ncAFM exchange parameter and magnetic anisotropy energy lead to a high Néel temperature of ~30 K for the bilayer. CoBi2Te4 has good stability and robust insulating electronic states. The topological nature in bilayer CoBi2Te4 is determined by an obvious band inversion and a nonzero topological invariant (Z2 = 1), which confirms an intrinsic ncAFM TI. At the same time, a flat band has been obtained in the edge state of (210) nanoribbon. The appearance of the flat band is attributed to the intralayer ncAFM coupling, because it is still preserved in the (210) nanoribbon of CoBi2Te4-Bi2Te3 heterostructure. These results provide a new way to achieve flat bands.
About the presenter
Ziyuan Zhao is a PhD Student with CI Nikhil Medhekar undertaking research linked with FLEET’s Research Theme 1, Topological Materials.