Emerging topological states in quasi-two-dimensional materials

5 years ago

Emerging topological states in quasi-two-dimensional materials

Jianfeng Wang, Wenhui Duan, Yong Xu, Huaqing Huang

Inspired by the discovery of graphene, various two-dimensional (2D) materials have been experimentally realized, which exhibit novel physical properties and support promising applications. Exotic topological states in 2D materials (including quantum spin Hall and quantum anomalous Hall insulators), which are characterized by nontrivial metallic edge states within the insulating bulk gap, have attracted considerable attentions in the past decade due to their great importance for fundamental research and practical applications. They also create a surge of research activities and attract extensive efforts to search for new topological materials in realistic 2D/quasi-2D systems. This review presents a comprehensive survey of recent progress in designing of topological states in quasi-2D materials, including various quantum well heterostructures and 2D atomic lattice structures. In particular, the possibilities of constructing topological nontrivial states from commonly used materials are discussed and the ways of enlarging energy gaps of topological states and realizing different topological states in a single material are presented. WIREs Comput Mol Sci 2017, 7:e1296. doi: 10.1002/wcms.1296 For further resources related to this article, please visit the WIREs website. Two typical topological states in quasi-two-dimensional materials: quantum spin Hall state and quantum anomalous Hall state. These topological states are characterized by insulating bulk but metallic edge states connecting conduction and valance bands in the bulk band gap. In quasi-two-dimensional materials, the quantum spin Hall state has time-reversal symmetry protected gapless helical edge states on edges, where two states with opposite spin polarizations counterpropagate at a given edge. While the quantum anomalous Hall state has a topological protected chiral edge state, where electric current flows unidirectionally along the edge.

Publisher URL: http://onlinelibrary.wiley.com/resolve/doi

DOI: 10.1002/wcms.1296