First-principles prediction of quantum anomalous Hall effect in the O-functionalized TiVC MXene

The quantum anomalous Hall (QAH) effect, which enables quantized Hall resistance without an external magnetic field, has attracted significant attention in two-dimensional materials for potential applications in low-power electronic devices. In this work, utilizing first-principles calculations, we find that the O-functionalized TiVC MXene (TiVCO2) monolayer, which is previously proposed as an energy material, will be a promising QAH system. The TiVCO2 monolayer possesses robust structural stability from dynamic, thermal, and mechanical perspectives and exhibits intrinsic ferromagnetism with a high Curie temperature of 370 K. Without the spin–orbit coupling (SOC), the TiVCO2 monolayer is a half-metal with quadratic non-Dirac dispersions around the Fermi level. After incorporating SOC, a sizable bandgap opens at the Γ point, but the nontrivial gap is positioned below the Fermi level owing to the valley polarization at the corners of the Brillouin zone. Through electric field modulation or strain engineering, the Fermi level can be adjusted into the SOC gap, giving rise to a QAH insulating state in the TiVCO2 monolayer. The nontrivial topology of the TiVCO2 monolayer is characterized by a quantized Hall conductance and a single gapless edge state in the bulk gap, confirming a non-zero Chern number of C=1. By the hybrid functional calculation, the strained system is revealed to have a sufficient SOC bandgap for the room-temperature QAH effect. Our study demonstrates that the double-metal MXenes can serve as experimentally accessible materials for achieving the intriguing QAH state.