The ultrathin topological insulator sodium bismuthide (Na3Bi) can switch to being a conventional insulator when an electric field is applied. This “off-on” effect, discovered by researchers in Australia, the US and Singapore, could be exploited to make the first ever working transistors from topological materials.

Topological insulators, also known as 2D quantum spin Hall insulators, are materials that are electrical insulators in the bulk but can conduct electricity on their surface via special spin-polarized surface electronic “edge” states. “Electrons travelling along these ‘topologically protected’ states can only travel in one direction and thus do not back-scatter,” explains team leader Mark Edmonds of the School of Physics and Astronomy at Monash University in Australia. “This means they can carry electrical current with near-zero dissipation of energy since back-scattering is what causes electrical resistance in conventional conductors, which wastes energy. The materials could thus be used to make energy-efficient devices like transistors and might even be the answer to the increasing challenge of energy wasted in modern CMOS-based computing, which accounts for 8% of global electricity use, and which is doubling every decade.”

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