Surface and Edge States in Topological Semi-metals

TL;DR

This paper investigates the surface and edge states in topological semi-metals using a 6-band Kane model, demonstrating their properties, effects of strain, and potential for spin Hall effects, with implications for future experiments.

Contribution

It provides a detailed analysis of surface states in topological semi-metals and shows how strain can induce a true topological insulator phase, predicting observable edge states and spin Hall effects.

Findings

Surface states are divided into two parts in the energy spectrum.

Uniaxial strain induces a band gap and moves the Dirac crossing into it.

Disorder enhances the spin Hall effect in thin film semi-metals.

Abstract

We study the topologically non-trivial semi-metals by means of the 6-band Kane model. Existence of surface states is explicitly demonstrated by calculating the LDOS on the material surface. In the strain free condition, surface states are divided into two parts in the energy spectrum, one part is in the direct gap, the other part including the crossing point of surface state Dirac cone is submerged in the valence band. We also show how uni-axial strain induces an insulating band gap and raises the crossing point from the valence band into the band gap, making the system a true topological insulator. We predict existence of helical edge states and spin Hall effect in the thin film topological semi-metals, which could be tested with future experiment. Disorder is found to significantly enhance the spin Hall effect in the valence band of the thin films.