Fig. 1: Second bandgap induced by band inversion.
From: Magneto-transport evidence for strong topological insulator phase in ZrTe5
a Side-by-side comparison of the zero-field kz dispersion of the normal (red) and inverted (blue) bands. The dispersions are produced using Eq. (3) with practical band parameters16, vFz = 5 × 104 m/s, M = 10 meV, \({{{{{{{{\mathscr{B}}}}}}}}}_{{{{{{\mathrm{z}}}}}}}\,=\,-0.3\) eV nm2 (normal), and \({{{{{{{{\mathscr{B}}}}}}}}}_{{{{{{\mathrm{z}}}}}}}\,=\,0.3\) eV nm2 (inverted), leading to a second energy extremum at the ζ point for the inverted band. b kz dispersion of the low-lying electron LLs of the normal and inverted bands in a at B = 10 T. Here, B∥z direction, and we use an average value for the band parameters in the x-y plane, including vF,⊥ = 5 × 105 m/s and \({{{{{{{{\mathscr{B}}}}}}}}}_{\perp }=0.05\) eV nm2. Integer n denotes the LL index. c Calculated DOS oscillations as a function of magnetic field with a constant electron density of 4 × 1017 cm−3.
