Fig. 2: The two energy bands in the vicinity of the middle of a 2-fold rotation axis.
From: Quasi-Dirac points in electron-energy spectra of crystals
The rotation axis coincides with the z axis (with pz = 0 being its middle). In the construction of the figure, dispersion relation (12) with the first set of the parameters from Table 2 has been used. The solid lines show the case of ZrTe5 (Δ ≈ 0); the dotted line marks the position of the Fermi level in this material (εF ≈ 36.1 meV, mvxvy ≈ 1.06 eV). Even below this level, a deviation of the dispersion from the linear law is visible. The black and red dashed lines correspond to the bands when Δ/(mvxvy) = 0.1 and Δ/(mvxvy) = − 0.065 (i.e., before and after the band inversion), respectively. At \(\Delta < {\Delta }_{{{{\rm{cr}}}}}=-{v}_{z}^{2}/({\alpha }_{c}+{\alpha }_{v})\approx -11.4\) meV, instead of the quasi-Dirac point with the gap 2∣Δ∣ at pz = 0, the two quasi-Dirac points with the gap \(2{[{\Delta }_{{{{\rm{cr}}}}}(2\Delta -{\Delta }_{{{{\rm{cr}}}}})]}^{1/2}\) exist at \({p}_{z}^{2}=2({\Delta }_{{{{\rm{cr}}}}}-\Delta )/({\alpha }_{c}+{\alpha }_{v})\).
