How many states of matter do you know about? It’s not just solids, liquids, gases, and maybe plasmas that we have to think about when we talk about the states of matter. Beyond these there’s an entire catalogue of matter alternatives: Bose–Einstein condensate, degenerate matter, supersolids/superfluids, quark-gluon plasma, etc. The difference is that all those alternatives are lab-created and don’t have much place out in the real world of nature. Researchers at Japan’s Tohoku University came up with an entirely new state of matter with an unusual combination of properties—insulator, superconductor, metal, magnet. The team, led by Kosmas Prassides, says they’ve created what’s called a Jahn-Teller metal by doping rubidium, a strange alkali metal element, into buckyballs, a pure carbon structure which has a spherical shape from a series of interlocking polygons.
Superconducting lattices of fullerides – C60 plus three alkali-metal atoms – have been studied for more than two decades, and provide an interesting test bed. This is because the distance between fulleride molecules and hence the electronic properties of the material can be adjusted by applying pressure to the material or doping it with different kinds of atoms.
The new state was found by changing the distance between neighbouring buckyballs by doping the material with rubidium. While they were tweaking the pressure between the buckyballs, the team came across a phase shift that transformed the material from an insulator into a conductor, a process called the Jahn-Teller Effect that was first predicted in 1937. Appropriately, the team is calling this novel material a Jahn-Teller metal. Jahn-Teller effect is a process used in chemistry to describe how at low pressures, the geometric arrangement of molecules and ions in an electronic state can become distorted.
The team’s discovery is the first time anyone has ever witnessed the Jahn Teller effect – the change from an insulator to a conductor – in action. The researchers hope that discovery of a new state of matter in a material that appears to be an insulator, superconductor metal and magnet all rolled into one, could lead to the development of more effective high-temperature superconductors. This new state of matter allows scientists to transform an insulator, which can’t conduct electricity, into a conductor by simply applying pressure.
By applying or removing pressure, it’s possible to boost the conductivity of what may have been an insulator at lower pressures. High pressure: conductivity. This is what the rubidium atoms do: apply pressure. Usually when we think about adding pressure, we think in terms of squeezing something, forcing its molecules closer together by brute force. But it’s possible to do the same thing chemically, tweaking the distances between molecules by adding or subtracting some sort of barrier between them—sneaking in some extra atoms, perhaps.
What happens in a Jahn–Teller metal is that as pressure is applied, and as what was previously an insulator becomes a metal, the effect persists for a while. The molecules hang on to their old shapes. So, there is an overlap of sorts, where the material still looks an awful lot like an insulator, but the electrons also manage to hop around as freely as if the material were a conductor. This is important because this transition from insulator to metal is also a transition from insulator to potential superconductor. The resulting metal just needs low enough temperatures and all of a sudden its electrons start pairing up and skipping around, with the result being a sudden drop to exactly zero electrical resistance. This is obviously a very desirable property. I.e. Jehn-Teller metals involve some other electron pairing mechanism, that might mean the possibility of superconductivity occurring at not-so-cold temperatures.
Superconductors are a large and diverse group of materials that offer zero resistance to electrical currents when cooled below a critical temperature (TC). Due to lack of resistance there is no loss of energy either in form of heat or sound or any other form. In normal cases when metals are used to transmit electricity there is electrical resistance in the form of heat which results in loss of energy. On the other hand if a material is superconductor of electricity then electrons pair up and start moving throughout the superconducting materials without any resistance and hence no loss of energy. However, scientists have seen that superconductivity can be achieved only at relatively higher temperatures i.e. very cold temperature.
What makes this discovery so significant is that from here, there’s one more step required to turn the material into a superconductor, a material with zero resistance, which revolutionise how we use and produce electricity. If the complete potential of superconductors is realized, we may solve many major problems related to energy in the world.