Monash physicists discover critical new development with major implications for topological transistors

Over the last decade, there has been much excitement about topological insulators – new materials that conduct electricity only on their edges, recognised by the Nobel Prize in Physics only two years ago.

Particularly exciting is their potential use in topological transistors – a proposed new generation of ultra-low energy electronic devices.

Now, FLEET researchers at Monash University, Australia, have for the first time successfully ‘switched’ a topological insulator off and on via application of an electric-field—the first step in creating a functioning topological transistor.

Ultra-low energy electronics such as topological transistors would allow computing to continue to grow, without being limited by available energy as we near the end of achievable improvements in traditional, silicon-based electronics (a phenomenon known as the end of Moore’s Law).

Study authors (from left) Dr Mark Edmonds, James Collins and Prof Michael Fuhrer are in the School of Physics and Astronomy at Monash University.

“Ultra-low energy topological electronics are a potential answer to the increasing challenge of energy wasted in modern computing,” said study author Professor Michael Fuhrer, from the Monash School of Physics and Astronomy, and Director of the ARC Centre for Future Low-Energy Electronics Technologies (FLEET).

“Information and Communications Technology (ICT) already consumes 8% of global electricity, and that’s doubling every decade,” he said.

The study Electric Field-Tuned Topological Phase Transition in Ultra-Thin Na3Bi was published today in Nature and is a major advance towards that goal of a functioning topological transistor.

How it works: Topological materials and topological transistors

Topological insulators are novel materials that behave as electrical insulators in their interior, but can carry a current along their edges.

“In these edge paths, electrons can only travel in one direction,” said study lead Dr Mark Edmonds, a lecturer from the School of Physics and Astronomy. “And this means there can be no ‘back-scattering,’ which is what causes electrical resistance in conventional electrical conductors.”

“Unlike conventional electrical conductors, such topological edge paths can carry electrical current with near-zero dissipation of energy, meaning that topological transistors could burn much less energy than conventional electronics. They could also potentially switch must faster,” said Dr Edmonds.

The study has shown for the first time that a material can switch at room temperature, which is crucial for any viable replacement technology.

ICT energy use, the end of Moore’s Law and ‘Beyond CMOS’ solutions

The overarching challenge behind the work is the growing amount of energy used in information and communication technology (ICT), a large component of which is driven by switching:

“Each time a transistor switches, a tiny amount of energy is burnt, but there are trillions of transistors in the world, all switching billions of times per second, so this energy adds up very quickly,” Dr Edmonds said.

For many years, the energy demands of an exponentially growing number of computations was kept in check by ever-more efficient, and ever-more compact CMOS (silicon based) microchips – an effect related to the famous ‘Moore’s Law’. But as fundamental physics limits are approached, Moore’s Law is ending, and there are limited future efficiencies to be found.

“The information technology revolution has improved our lives, and we want it to continue,” said Professor Fuhrer.

“But for computation to continue to grow, to keep up with changing demands, we need more-efficient electronics.”

“We need a new type of transistor that burns less energy when it switches.”

“This discovery is a step in the direction of topological transistors that could transform the world of computation.”

Fast facts about ICT energy use:

  • The energy burnt in computation accounts for 8% of global electricity use
  • ICT energy use is doubling every decade
  • ICT contributes as much to climate change as the aviation industry
  • Moore’s Law, which has kept ICT energy in check for 50 years, will end in the next decade.

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