Figure 4
(a) The PBE + vdW bandstructure of 4L-BP is plotted in the 2D brillouin zone for Eext = 0.72 V/Å, above the critical field. The Dirac cone appears at ±Λ. (b) The PBE + vdW bandstructure along Y-Γ-X, for the three different Eext above the critical value, namely Eext = 0.51 (black), 0.72 (red) and 0.93 (green) V/Å. (c) The bandgap that opens along Γ-X direction, 
, is plotted against (Eext−Ec) for 4L-BP (blue line) and 8L-BP (red line). Note that the values of Ec for 4L-BP and 8L-BP are 0.48 and 0.28 V/Å, respectively. (d) The Fermi velocity along kx, 
(red dashed line) and along ky, 
(red solid line) are plotted as a function of (Eext−Ec) for 4L-BP. vF is calculated as vF = δE/δk at the Dirac point.
