Prediction of two-dimensional organic topological insulator in metal-DCB lattices

Abstract

Based on first-principles calculations, we systematically investigated a two-dimensional (2D) organometallic framework consisting of metal atoms (elements from groups IIIA, IVA, VA, VIA, IB, and Pt) and dicyanobenzenes (DCBs). Our stability analysis showed that the system prefers the buckled structure in metals with p-orbital valence electrons, whereas in metals with d-orbitals, the planar phase is preferable. Topological invariants (Z2) of these systems were calculated, and they are identified as 2D intrinsic organic topological insulators. Au- and Bi-DCB are exemplar materials with the largest bandgaps within IB and VA groups. Moreover, Au-DCB exhibits robustness of its topological phase against strain. Furthermore, the topologically protected edge states in Au-DCB are identified to further verify the Z2 invariant. Interestingly, utilizing hole doping in Bi-DCB leads to a nearly flat Chern band and results in the quantum anomalous Hall phase. Our results suggest that these organometallic frameworks are promising for potential applications in quantum spintronics with the merits of low cost and ease of synthesis.