Topological Surface States Protected from Backscattering by Chiral Spin Texture

Topological insulators: no turning back Topological insulators are materials in which a relativistic effect known as spin–orbit coupling gives rise to a bulk insulating gap and surface states that resemble so-called chiral edge states in the quantum Hall effect. It has been theoretically suggested that the quantum mechanical spin degree of freedom of such surface edge states may be protected against scattering due to topology, which could be useful for spintronics and quantum computing. Now Roushan et al . provide the experimental confirmation of this important prediction. Using scanning tunnelling and angle-resolved photoemission microscopy they are able to demonstrate that, despite strong atomic scale disorder in their system, backscattering between surface states with opposite momentum and opposite spin is absent.