Material that behaves as an insulator in its interior but whose surface contains conducting states.
There are two main classes: three-dimensional (3D) and two-dimensional (2D) material systems. The 2D topological insulators are expected to exhibit one dimensional dissipationless edge channels, while the 2D plane inside is insulating .
Materials of special interest are: HgTe, Bi₂Se₃, Bi₂Te₃, Sb₂Te₃, Stanene, Heusler compounds, special oxides and others.