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Abstract

Recently, the long-sough quantum anomalous Hall effect was realized in a
magnetic topological insulator. However, the requirement of an extremely
low temperature (approximately 30 mK) hinders realistic applications.
Based on ab initio band structure calculations, we propose a quantum
anomalous Hall platform with a large energy gap of 0.34 and 0.06 eV on
honeycomb lattices comprised of Sn and Ge, respectively. The
ferromagnetic (FM) order forms in one sublattice of the honeycomb
structure by controlling the surface functionalization rather than
dilute magnetic doping, which is expected to be visualized by spin
polarized STM in experiment. Strong coupling between the inherent
quantum spin Hall state and ferromagnetism results in considerable
exchange splitting and, consequently, an FM insulator with a large
energy gap. The estimated mean-field Curie temperature is 243 and 509 K
for Sn and Ge lattices, respectively. The large energy gap and high
Curie temperature indicate the feasibility of the quantum anomalous Hall
effect in the near-room-temperature and even room-temperature regions.