Physics researchers have just defied our current understanding of conductors by introducing a metal that has the ability to conduct electricity without conducting heat. This discovery contradicts the Wiedemann-Franz Law, which argues that good conductors of electricity will be proportionally good at conducting heat. This law has long been used to explain why motors and appliances warm up with regular use.
Now, a team in the US has proven this isn’t the case for metallic vanadium dioxide. The material has already gained attention for its ability to transform from a see-through insulator to a conductive metal at 67 degrees Celsius—but this only increases its mystery.
“This was a totally unexpected finding,” lead researcher Junqiao Wu, from Berkeley Lab’s Materials Sciences Division. “It shows a drastic breakdown of a textbook law that has been known to be robust for conventional conductors. This discovery is of fundamental importance for understanding the basic electronic behavior of novel conductors.”
While shocking, this property could be used to convert wasted heat from engines and appliances back into electricity. It could also be revolutionize cooling systems. We already know of several other materials that conduct electricity better than heat, but only reveal those properties when temperatures drop hundreds of degrees below zero—rendering them useless for any real application. Vanadium dioxide is only used as a conductor at warm temperatures, which makes it a lot more practical.
To discover this new property, the research team studied the way electrons move within the material’s crystal lattice, as well as how much heat was being generated. They discovered that the thermal conductivity that could be attributed to the electrons in the material was at least 10 times smaller than Wiedemann-Franz law predicts.
“The electrons were moving in unison with each other, much like a fluid, instead of as individual particles like in normal metals,” Wu noted.
When the researchers mixed the vanadium dioxide with other materials, they found they could ‘tune’ the amount of electricity and heat it could conduct—a feature that could be remarkably useful in future applications.
“This material could be used to help stabilize temperature,” Fan Yang, another one of the researchers, noted. “By tuning its thermal conductivity, the material can efficiently and automatically dissipate heat in the hot summer because it will have high thermal conductivity, but prevent heat loss in the cold winter because of its low thermal conductivity at lower temperatures.”