Scientists discover quantum phase transition in pressurized cuprate superconductors

The discovery of cuprate high-temperature superconductors in 1986 impacted science and technology considerably and continues to fascinate the communities of condensed matter physics and material sciences because they host the highest ambient-pressure superconducting transition temperature and unconventional electronic behavior. However, the underlying mechanism of the superconductivity is yet an unsolved mystery. Searching for the universal links between the superconducting state and its neighboring quantum states is considered an effective approach to elucidate the high temperature superconducting mechanism.

Recently, Prof. Sun Liling's team from the Institute of Physics (IOP) of the Chinese Academy of Sciences, in collaboration with Profs. Xiang Tao, Zhou Xingjiang and hu Jiangping Hu from IOP, Prof. Gu Genda from the Brookhaven National Laboratory and Prof. Lin Chengtian from the Max Planck Institute, has discovered the pressure-induced quantum transition from superconducting state to insulating-like state in bismuth-based cuprate superconductors, through their state-of-the-art in-situ high-pressure measurements.

These experimental results reveal that the observed quantum phase transition is universal in the bismuth-bearing cuprate superconductors, regardless of the doping level and the number of copper oxide (CuO₂) planes in a unit cell.

It is a grand surprise for them that the system enters into an insulating-like state after the superconductivity is fully suppressed, because it is well known that the ground state of the over-hole-doped non-superconducting cuprate is a metallic state, and naively one expects that by applying pressure the bandwidth should be increased.

As a result, the system should become more metallic, instead of insulating-like. This discovery of the universal quantum transition provides a fresh challenge and a new opportunity for better understanding the mechanism of superconductivity in these materials.

The study, titled "Quantum phase transition from superconducting to insulating-like states in a pressurized cuprate superconductor," has been published in Nature Physics.