Two-dimensional obstructed atomic insulators with fractional corner charge in the MA2Z4 family

Article

关键词: SCHEMES;    CATALOG;   

DOI  :  10.1103/PhysRevB.106.155144

来源: SCIE

【 摘 要 】

According to topological quantum chemistry (TQC), a class of electronic materials has been called obstructed atomic insulators (OAIs), in which a portion of valence electrons necessarily have their centers located on some empty Wyckoff positions (WPs) without atom occupation in the lattice. The obstruction of centering these electrons coinciding with their host atoms is nontrivial and results in metallic boundary states when the boundary is properly cut. Here, on the basis of first-principles calculations in combination with TQC analysis, we propose two-dimensional MA2Z4 (M = Cr, Mo, and W; A = Si and Ge; Z = N, P, and As) monolayers are all OAIs. A typical case is the recently synthesized MoSi2N4 (alpha 1-MoSi2N4). Although both alpha 1- and alpha 2-MoSi2N4 monolayers are topological trivial insulators, it has valence electrons centering empty WPs and the in-gap corner states at the three vertices of triangle-shaped nanodisk samples respecting C3 rotation symmetry, which can be explained by the filling anomaly of electrons. In addition, the alpha 2-MoSi2N4 monolayer exhibits unique OAI-induced metallic edge states along the (11 over bar ) edge. The readily synthesized MoSi2N4 is quite stable and has a large bulk bandgap of 1.94 eV, which makes the identification of these edge and corner states most possible for experimental clarification.

【 授权许可】

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