Interplay between anisotropic spin texture and large gap topological insulating phases in functionalized MXenes

Massive attention has been given to two-dimensional (2D) MXenes due to their predicted topological phase and promising diverse applications. Using first-principles with hybrid functional calculations, we systematically conducted an extensive study on M2C (M = Mo, or W) in 1T and 2H structures with various surface terminations T2 (T = H, O, OH, F, Cl, Br, or I). Pristine Mo2C and W2C compounds are in the 2H phase. Upon functionalization of H, O, OH and F, they retain the 2H structure, whereas Cl, Br, and I functionalization, the structures transform to 1T phase. Notably, M2CO2 are found to be 2D topological insulators (TIs) with sizable nontrivial bandgaps as large as 666 meV. Interestingly, 2H M2CO2 exhibits not only large-gapped Zeeman-type spin splitting at K-point but also anisotropic Rashba spin splitting at Gamma-point. The successful synthesis of pristine Mo2C and our theoretical study pave a path for future applications of MXene-based 2D TIs.

Automated summary

This study systematically investigates the properties of M2C (M = Mo or W) with different surface functionalizations in 1T and 2H structures using first-principles and hybrid functional calculations. The results show that M2CO2 can be used as size-controllable 2D topological insulators, which have promising potential applications.