Two-dimensional higher-order topology in monolayer graphdiyne

Based on first-principles calculations and tight-binding model analysis, we propose monolayer graphdiyne as a candidate material for a two-dimensional higher-order topological insulator protected by inversion symmetry. The higher-order topology is manifested in the filling anomaly and charge accumulation at two corners. Nontrivial bulk topology is correctly captured only when contributions from core levels ( *p_xy* and *s* orbitals) are included, confirmed by Wilson loop calculations. The higher-order band topology also influences the corresponding three-dimensional material (ABC-stacked graphdiyne), hosting monopole nodal lines and hinge states.

Eunwoo Lee, Rokyeon Kim, Junyeong Ahn, Bohm-Jung Yang