Heat Diode Paves the Way For Thermal Computing

There’s no escaping the insidious effects of heat in microchips. But there may now be a way of controlling it. Wataru Kobayashi at Waseda University in Japan and a few friends have built a rectifier that allows a heat current to travel in one direction but not the other.

For some time, researchers have predicted that thermal rectifiers would be possible with materials which have thermal conductivities that change with temperature. The trick is to find a material with a high thermal conductivity at low temperatures and a low thermal conductivity at high temperatures, and then to marry it with a material with exactly the opposite characteristic.

Kobayashi and co found just such a match in two types of perovskite cobalt oxides (LaCoO3 and La0.7Sr0.3CoO3). Glued together, they form a diode-like device that allows a heat current to pass in one direction but not the other.

That’s impressive because it’s the first time anybody has demonstrated heat rectification in a bulk solid (it’s been done with individual electrons in superconductors and in single nanotubes).

One obvious application is in heat sinks for microchips but some significant improvements will be needed to carry the kind of heat currents involved.

But Kobayashi and co have bigger prey in mind. They say: ” Owing to the controllability of the heat current, the thermal rectifier can be utilized for future practical application such as a thermal transistor, thermal logic gates, and a thermal memory.”

What they don’t say is how thermal information processing might be used. Presumably in places where electrical power is hard to come by and where excess heat would otherwise go to waste. Thinking caps on.

Ref: arxiv.org/abs/0910.1153: An Oxide Thermal Rectifier