Fig. 2.

The four distinct regimes of Landau level occupancy in TaAs up to 65 T. TaAs hosts two pairs of Weyl fermi surfaces (W1 and W2) with similar quantum limits for this field orientation; one pair of Weyl nodes is shown here along with the trivial hole surface. Resistivity of TaAs at temperatures between 0.7 K and 20 K, for $\mathbf{J}\mid \mid \mathbf{B}\mid \mid \mathbf{c}$ (a) and for $\mathbf{J}\perp \left(\mathbf{B}\mid \mid \mathbf{c}\right)$ (b), from 0 to 65 T. c, Schematic of the Landau level (LL) structure and occupancy for the parabolic hole pockets (red lines) and Weyl electron pockets (blue lines). Gray curves are the B = 0 dispersions without LLs. Region I is from 0 to 7.5 T, where both hole and electron pockets exhibit quantum oscillations. Between 7.5 and 18 T (region II) the electron pockets are in the n = 0 LL, whereas the hole pocket is still in the n = 1 LL. Between 18 and 36 T (region III) the hole pocket is also in the n = 0 LL. At 36 T the last oscillation, corresponding to emptying the n = 0 LL of the hole pocket, can be seen in ρ_xx. Above 36 T (region IV) the only occupied states at the chemical potential are in the n = 0 LL of the Weyl electron pockets, and the chemical potential shifts to maintain overall carrier number (n_e−n_h). The faded region IV represents the mixing of the Weyl nodes above 50 T (Fig. 3)