The cones in this image illustrate the equations of motion of electrons when an external magnetic field is applied to the bismuth alloy engineered for the study. Green lines and purple lines represent electrons that generate and absorb energy, respectively.

Cooling off: Unusual electron movement could cool cleantech

Quantum science is a pretty complex concept. But researchers at Ohio State University are making it easy to understand a big outcome from their quantum discovery: Their specially engineered metal alloy could be used in a “heat switch” that cools clean energy and computing technologies.

The tech

The researchers created the alloy from the elements bismuth and antimony. Its electrons exhibit the unexpected behavior of moving like massless photons, or light. The alloy is in a class of quantum materials called Weyl semimetals, whose electrons don’t behave as expected. 

The alloy’s unusually behaving electrons manipulate heat in atypical ways when they are exposed to a magnetic field. Some of the electrons generate heat — or energy — and others absorb energy. This makes the material act as an energy pump and results in a 300% increase in its thermal conductivity. This function stops when the magnet is removed.

“The heat disappears and reappears elsewhere — it is like teleportation,” Joseph Heremans, OSU professor of mechanical and aerospace engineering, said in a news release. “It only happens under very specific circumstances predicted by quantum theory.” 

One catch is that the process only works when the material is at an extremely low temperature — negative 100 degrees Fahrenheit or less.

What it means

This material holds huge potential as a heat switch, similar to how a transistor switches electrical currents or a faucet switches water. The bismuth-antimony alloy would enable a heat switch with no moving parts that is simply controlled with a magnet.

“Solid-state heat switches without moving parts are extremely desirable, but they don’t exist,” Heremans said. “This is one of the possible mechanisms that would lead to one.”

Now that the researchers understand how this material’s processes function, they can work on possible applications. For example, this type of heat switch could provide a cooling mechanism for computers or increase solar-thermal power plant efficiency.

“Now we know what materials to look for and what purity we need,” Heremans said. “That is how we get from discovery of a physical phenomenon to an engineering material.”

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