Direct tuning of large-gap quantum spin Hall effect in mono transition metal carbide MXenes

Abstract

Some two-dimensional (2D) MXenes topological insulators (TIs) show a large nontrivial bandgap, which strongly depends on the relativistic effect or electron correlation effects. However, the factors of orbitals are always...

Tuning d-orbitals to control spin–orbit coupling in terminated MXenes

“…28–35 These orbital hybridizations contribute to the degenerate orbits around the Fermi level and play noticeable roles. 25,26 We note that the nontrivial bandgap in the F-terminated Ta 2 CF 2 monolayer reaches 0.810 eV (HSE06), 27 as compared to the 5d MXene TIs, where the gap of the O-terminated W 2 CO 2 monolayer is 0.472 eV (HSE06). 20 Such a difference in the gap is unexpected for similar 5d MXene TIs, and the inadequacy of the relativistic effect in elucidating the increasing gap values is apparent.…”

“…15,16 Recently, theoretical predictions have identified diverse MXene monolayers as potential 2D TIs, with their surfaces primarily terminated by oxygen (O) and fluorine (F) groups. [17][18][19][20][21][22][23][24][25][26][27] However, due to the relativistic effect, 2D MXene TIs with a large spin-orbit coupling (SOC) effect have mostly been limited to materials with heavy elements. In other words, the dependency on elements is still indispensable for increasing the nontrivial bandgap.…”