Soon, computers to run on heat, rather than electricity

Computers may soon be able to recycle part of their own waste heat, using a material being studied by researchers.

The material is a semiconductor called gallium manganese arsenide.

Researchers at the Ohio State University describe the detection of an effect that converts heat into a quantum mechanical phenomenon - known as spin - in a semiconductor.

Once developed, the effect could enable integrated circuits that run on heat, rather than electricity.

This research merges two cutting-edge technologies: thermo-electricity and spintronics, explained team leaders Joseph Heremans, Ohio Eminent Scholar in Nanotechnology, and Roberto Myers of the Ohio State University.

Myers and Heremans have been trying to combine spintronics with thermo-electronics - that is, devices that convert heat to electricity.

"Spintronics is considered as a possible basis for new computers in part because the technology is claimed to produce no heat. Our measurements shed light on the thermodynamics of spintronics, and may help address the validity of this claim," Nature quoted Heremans as saying.

In one possible use of thermo-spintronics, a device could sit atop a traditional microprocessor, and siphon waste heat away to run additional memory or computation.

The researchers studied how heat can be converted to spin polarisation- an effect called the spin-Seebeck effect. Researchers at Tohoku University first identified it. Those researchers detected the effect in a piece of metal, rather than a semiconductor.

The new measurements, carried out by team member Christopher Jaworski have provided the first independent verification of the effect in a semiconductor material called gallium manganese arsenide.

Samples of this material were carefully prepared into thin single-crystal films by collaborators Shawn Mack and David Awschalom at the University of California, who also assisted with interpretation of the results.

In the experiment, they heated one side of the sample, and then measured the orientations of spins on the hot side and the cool side. On the hot side, the electrons were oriented in the spin-up direction, and on the cool side, they were spin-down.

The researchers also discovered, to their own surprise, that two pieces of the material do not need to be physically connected for the effect to propagate from one to the other.

"We figured that each piece would have its own distribution of spin-up and spin-down electrons.

"Instead, one side of the first piece was spin up, and the far side of the second piece was spin down. The effect somehow crossed the gap," said Myers.
 
Despite these new experiments, the origin of the spin-Seebeck effect remains a mystery.

The findings were published in the journal Nature Materials.