Beschreibung:
<jats:title>Significance</jats:title>
<jats:p>Topological insulators possess metallic surfaces states that are generally perceived as electrons and holes with a linear symmetric dispersion around the Dirac point. In this work, we show that this symmetry is significantly distorted in the 3D topological insulator-strained HgTe. In thermopower experiments, we show a distinctively different behavior of surface electrons and holes that originates from a strongly asymmetric dispersion of surface states. Nonetheless, the surface states themselves remain topologically protected as evidenced by the observation of an ambipolar surface quantum Hall effect and quantum oscillations in the thermoelectric response. This observation shows that the physics of topological surface states in 3D topological insulators is far richer than previously envisaged.</jats:p>