Physicists report that they have identified a metal that behaves in a manner that defies our current understanding about them, by conducting electricity without conducting heat, thus circumventing the prevalent Wiedemann-Franz Law for conductors.
The law states that in a metal with free moving electrons, the thermal conductivity and the electrical conductivity is proportional to the temperature, meaning heat conductivity is an ineluctable part when a metal conducts electricity, which is why we can observe electrical appliances getting heated.
Researchers have isolated metallic Vanadium Oxide (VO2) that’s an exception to the law. VO2 is already known among physicists to exhibit a property that enables them to become a conductor from an insulator at precisely 67 degree Celsius (152 degrees Fahrenheit).
The lead researcher Junqiao Wu from Berkeley Lab’s Material Science Division has quipped that this phenomenon has broken down a fundamental law that’s known to explain conductivity in metals and can pave the way for a more comprehensive understanding of conductors.
This new discovery could also have practical applications by converting the wasted heat from appliances and turning them into electricity, which could be used again, thereby efficiently using the energy which would otherwise get lost into the atmosphere.
Researchers also know of some other materials that are better in conducting electricity than heat however for them to manifest them, it would require supercooling as they display those properties only when cooled to hundreds of degrees below zero, which isn’t energy efficient and makes it impractical however VO2 displays this property above room temperature, something that’s easy to achieve.
The researchers looked at the way the electrons moved within the material to decipher this enigma and found that the heat generated by this material was 10 times lesser than what was predicted by the theory.
They were able to attribute this phenomenon to the way the electrons moved in synchrony within the material, resembling a smoothly flowing fluid with less viscosity.
Usually electrons move sporadically in response to heat in metals however this strange harmonious symphony that they exhibit in VO2 prevents heat transfer effectively as there are fewer configurations available to them to jostle between.
They found that they could tune the amount of heat and electricity that VO2 can conduct by combining it with other materials like Tungsten which lowers the temperature at which it becomes metallic and also made it a better conductor of heat.
This means that Vanadium Oxide could dissipate heat at a certain temperature below which it will be an insulator. It also has the unique property that it is transparent at 30 degrees Celsius however it reflects infrared above 60 degrees Celsius, while remaining transparent to visible light at the same time.
As this material can be tuned to have high thermal conductivity during high temperatures, it could dissipate heat in summers, keeping the interiors cool whilst retaining heat during winters due to the low thermal conductivity at low temperatures, it could have a practical application as window coating that could dissipate unwanted heat and keep the indoors cooler compared to the outside, thereby precluding the need for air conditioners.
There’s a lot of research that has to go into this before we can exploit it commercially and put it to good use.
The research was published in Science in 2017.
A version of this article was first published in January 2017.