A group of 2D topological insulators BiX/SbX (X=H, F, Cl and Br) monolayers with extraordinarily large bulk gaps from 0.32 to a record value of 1.08 eV were predicated. These giant-gaps result from the strong spin-orbit interaction related to px and py orbitals of Bi/Sb atoms around the two valleys K and K′. The honeycomb structures of BiX monolayers remain stable even at a temperature of 600 K. The electric field-biased BiX/SbX monolayers become quantum valley Hall insulators, showing valley-selective circular dichroism. These features make the BiX/SbX monolayers an ideal platform to realize many exotic phenomena and fabricate new quantum devices.
- Zhigang Song
- Cheng-Cheng Liu
- Yugui Yao