Glass as topological insulators
doi:10.1038/nindia.2017.96 Published online 1 August 2017
Computer models have shown that topological insulators can be made from amorphous materials such as some forms of glass, opening avenues for a wide range of energy-efficient electronics and quantum computing1.
Topological insulators are wonderful materials that don’t allow electrons to travel through them, instead, being forced to travel on their surface at very high speeds without colliding with other electrons and atoms. Recent studies had shown that crystals could act as good topological insulators.
Physicists Vijay B. Shenoy and Adhip Agarwala from the Indian Institute of Science in Bangalore, have theoretically proved that amorphous solids could also act as topological insulators.
They simulated two-dimensional and three-dimensional structures whose lattice sites are randomly arranged. As electrons hop between neighbouring sites, by tuning parameters such as distance between lattice sites and energy bands, the structures undergo a quantum phase transition, giving rise to a topological phase.
Besides glass, they have shown that it is possible to make topological insulators in engineered systems. This could be done by randomly adding atoms, molecules or nanoclusters on the surface of an existing insulator.
“It is easier to synthesise topological insulators from amorphous solids than crystalline materials which require stringent controls,” says Shenoy.
1. Agarwala, A. et al. Topological insulators in amorphous systems. Phys. Rev. Lett.118, 236402 (2017)