Vanadium Dioxide breaks the rules of conductivity, according to scientists.
Vanadium Dioxide (VO2) is a newly discovered material with some curious properties. It is a metal capable of conducting electricity, but without heating up in the process. A team of international scientists led by scientists at the Department of Energy’s Lawrence Berkeley National Laboratory (Berkeley Lab) and at the University of California, Berkeley, have attempted to verify the metal’s behavior. They have confirmed that indeed, VO2’s electrons can carry charge without carrying heat.
The findings have just been published in the journal Science and could lead to a range of applications for the material, which turns from an insulator to a metal at 67 degrees Celsius. In most metals, electric and thermal conductivity go hand-in-hand, following something known as the Wiedemann-Franz Law. The law states that good conductors of electricity are also good conductors of heat. This is why, for example, your computer has heat sinks and fans. You simply cannot move a lot of electrons around without also generating heat… except when it comes to vanadium dioxide.
“This was a totally unexpected finding,” said the study’s lead investigator Junqiao Wu, a physicist at Berkeley Lab’s Materials Sciences Division and a UC Berkeley professor of materials science and engineering. “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.”
“The electrons were moving in unison with each other, much like a fluid, instead of as individual particles like in normal metals,” said Wu. “For electrons, heat is a random motion. Normal metals transport heat efficiently because there are so many different possible microscopic configurations that the individual electrons can jump between. In contrast, the coordinated, marching-band-like motion of electrons in vanadium dioxide is detrimental to heat transfer as there are fewer configurations available for the electrons to hop randomly between.”
Yang noted that there are more questions that need to be answered before vanadium dioxide can be commercialized, but also notes that it has great potential, and by doping the material with other metals, the conductivity (electrical and thermal) can be tuned for various purposes. There are other materials with similar properties, but they almost exclusively require cryogenic temperatures to function.