High-temperature quantum anomalous Hall effect on post-transition-metal-decorated graphene.

Quantum anomalous Hall (QAH) insulators are a highly promising class of materials for spintronic devices and quantum computations because of their precise quantization nature, robust properties against defects, and relatively low energy consumption for operation. To realize the QAH effect quantum spin Hall (QSH) insulators must be utilized, which requires transition metal doping or surface functionality control. Here, we propose a new way to introduce ferromagnetism to large-gap QSH insulators: we release the onsite magnetic momentum by increasing the lattice constants of stanene and germanene. If the lattice constant is increased to 9.5 Å, ab initio band structure calculations show that their spin–orbit coupling gaps are about 0.25 and 0.05 eV, respectively. Furthermore, the Curie temperatures, calculated by the Monte Carlo method, are 780 and 420 K. Both results indicate that the room-temperature QAH effect can be realized on these systems. We also provide a possible experimental realization of this system on the 2√3×2√3 graphene substrate. Our calculations predict the first room-temperature QAH insulator in the realistic materials system.