The Jahn-Teller metal is not one of the 3 (or 4 including plasma) states that occur naturally on Earth; this state allows a metal to have the properties of an insulator and a superconductor.
It is an intermediate state of matter confirming the Jahn-Teller distortion; by interacting with certain electrons (a more detailed description can be found in this Science Advances magazine article, a distorted crystalline structure allows a solid depicting characteristics of an insulator to also becomes a conductor.
The main breakthrough this brings is having a superconductors. Superconductors are extremely useful because they possess zero resistance, except the conditions require them to be cooled to extreme temperatures.
This state nonetheless suggests reproducing superconductors at a less extreme temperature.
Making it an economic way to make efficient electronics.