The effect of lattice termination on the Zeeman gap of topological edge states in the quantum spin Hall insulator WTe₂

We investigate the effect of the sample termination on the electronic properties of the recently discovered quantum spin Hall insulator WTe₂. For this purpose, we have derived a minimal 4-orbital tight-binding model by means of a combination of symmetry considerations, density-funcitonal theory calculations and experimental data. Here, we are going to present the results of our theoretical study including spectra of topological edge states and conductance calculations for various sample geometries with and without magnetic field.

We observe that the edge-state dispersion considerably depends on the lattice termination: for some terminations the edge-state spectrum features a Kramers doublet, or Dirac point, of topological states inside the bulk energy gap. For others, this Dirac point is ”buried” in the bulk continuum of bands. Here, we will show that this qualitative difference is strongly reflected in the electronic conductance under magnetic field. In particular, we find that the specific behavior is related to the type of Zeeman gap in the corresponding edge-state spectrum.