U. research could lead to speed-of-light computing

By David Self Newlin | Posted - Feb 18th, 2013 @ 11:46am

SALT LAKE CITY — Computer engineering is already hard enough — few of us out there know how that laptop we carry around all day actually works. Add Dirac fermions moving around a two dimensional electron gas in a spin-momentum locked state and boy, you've got a bit of a computational pickle on your hands.

On the upside, this complicated work is being done by scientists like Feng Liu and his team at the University of Utah, so we can eventually reap the benefits. They have been studying what are called topological insulators, and for the first time they've demonstrated that they can be made from organic materials.

A topoogical insulator is a material that conducts electricity on the edge, but won't conduct on the inside. They've got some interesting properties that should make them useful in the field of quantum computing.

Typical computing uses standard electricity to convey information in the form of ones and zeros. How fast that information moves is limited by the speed electrons can move through a conductor or semiconductor.

Liu's material, on the other hand, can make electricity move at the speed of light, with the aid of the special properties of organic topological insulators.

"We have demonstrated a system with a special type of electron — a Dirac fermion — in which the spin motion can be manipulated to transmit information," he said. "This is advantageous over traditional electronics because it's faster and you don't have to worry about heat dissipation."

On the surface of such an insulator, Dirac fermions form, which are particles that can exist only within the material and behave just like massless electrons. Because they are massless, they move at the speed of light, unlike much slower ordinary electrons; because they have a charge, they can be used to carry a current.

Moreover, their spin is locked to their direction of travel. If it's going one way, it spins up; the other direction it spins down. That means the Dirac fermions in the material can be used to carry ones and zeros, like any good computer circuit needs to do.

Liu said topological insulators have been studied for years, but they have always been made of inorganic compounds that can be expensive and come with lots of downsides. On the other hand, he's developed a carbon- and bismuth-based material that is cheap to make and is flexible. It could even be put in a flexible screen or plastic.

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