Extended Data Fig. 2: Band structure of bilayer WTe2 as a function of the external electric field.
From: Observation of the nonlinear Hall effect under time-reversal-symmetric conditions
a–d, With positive E fields, the global bandgap increases then decreases; with negative E fields, the global bandgap decreases. The evolution of the valence-band splitting at the Γ point (black arrows) of the global bandgap as a function of the E field are consistent with the picture in Extended Data Fig. 1. The green circle in d highlights the anti-crossing (a massive Dirac fermion) formed between the lowest two conduction bands at D > 0. Such a massive Dirac cone with a small gap (approximately 3 meV) leads to large Berry curvature near the gap edges, which is responsible for the additional sharp features in the \({V}_{baa}^{2\omega }\) data (Supplementary Information section V).
