Engineering topological phases in transition-metal-doped penta-hexa-graphene: towards spintronics applications

The roles of Pd and Pt doping in penta-hexa-graphene (PH-G) were studied using first principles DFT calculations, which may lead to a better understanding of the dopant effects and further help to expand the application potential of PH-G. We find that doping could significantly change the basic properties in PH-CX (X = Pd, Pt). Compared to PH-G, doping transforms these materials from semiconductors into conductors, resulting in the emergence of Dirac points near the Fermi level. Considering spin-orbit coupling (SOC), the topological insulator (TI) PH-CPd (PH-CPt) emerges, characterized by a nonzero topological invariant (Z₂ = 1) and a W-shaped band, with band gaps of 13.00 meV and 74.80 meV, respectively. Remarkably, pairs of gapless edge states can be observed. Moreover, we demonstrate that although the PH-CX structure is robust against external strain, both the band gap and topology can be effectively tuned. Based on the band analysis, we identify that the Rashba effect is observed even under tensile strain of up to 10%. The presented results not only greatly extend the design concept of doping to form two-dimensional topological materials but also provide potential applications in field-effect transistors (FETs) and other electronic devices.