Topological Insulator
A quantum material that behaves as an electrical insulator in its 3D interior bulk but features robust conducting metallic states on its 2D surface boundary.
Governing formula
Z₂ Topological Invariant ν = 1
SI unit
Quantum Phase Class
In depth
Surface states are topologically protected by time-reversal symmetry and strong spin-orbit coupling. Surface conduction electrons exhibit Dirac cone energy dispersion where spin is locked perpendicular to momentum, preventing backscattering from impurities.
Examples in the real world
Bismuth Selenide (Bi₂Se₃) and Bismuth Telluride (Bi₂Te₃) used in spintronics and topological quantum computing research.