Figure 1

(a) Lattice geometry for BiX/SbX monolayer (X=H, F, Cl and Br) from the top view (upper) and side view (lower), respectively. In a unit cell, BiX/SbX is related to Bi'X'/Sb'X' by an inversion operation. (b) The first Brillouin zone of BiX/SbX monolayers and the points of high symmetry. (c) Corresponding phonon spectrum for BiH monolayer.