This summer's biggest sensation for room-temperature, ambient-pressure superconductors is about to come to a close. Scientists seemed to have pieced together the puzzle for LK-99: "The material is not a superconductor," an article published in the journal Nature said.

A freelance science writer who holds a bachelor degree in physics from Columbia University and has worked at Fermilab as part of an internship, Dan Garisto put together different failed replications of LK-99's superconductivity from researchers across continents and published them on Nature.

The inception

In late July, a South Korean team led by experts from the Quantum Energy Research Center posted two papers on arXiv, claiming that they had synthesized the world's first room-temperature superconducting material under ambient pressure, known as LK-99, a modified-lead apatite crystal structure doped with copper.

"The superconductivity of LK-99 proved with the critical temperature, zero-resistivity, critical current, critical magnetic field, and Meissner effect," said the researchers.

Their discovery soon went viral, arousing excitement and skepticism.

Research teams worldwide have attempted to replicate the material but have yet to confirm the superconductivity of LK-99.

The crescendo

Researchers from A-list labs raced against the clock to verify the superconductivity of LK-99, but none could find a confirmation of the Korean team's claim.

Later on August 8, a team of researchers from the Institute of Physics under the Chinese Academy of Sciences (CAS) determined that the misleading phenomenon of LK-99 is a result of the copper sulfide (Cu2S) impurity contained in the material.

The team published a full study of their proof and pointed out that Cu2S undergoes a structural phase transition from a hexagonal structure at high temperatures to a monoclinic structure at low temperatures at around 100 degrees Celsius.

"When the phase transition occurs, the resistivity drops by 3-4 orders of magnitude, making the LK-99 sample look like superconductivity, but it's actually not," Luo Jianlin, a researcher on the Institute of Physics team, told CGTN via email.

A "crystal" resolution

Even with all the findings going against the claim, it is still hard to draw a conclusion on the properties of LK-99 as the material is very particular and the replicated samples contain varying impurities, Nature's article said.

However, on August 14, a team from Max Planck Institute for Solid State Research in Stuttgart, Germany, reported synthesizing pure, single crystals of LK-99 using a special crystal growth technique.

Based on this material, the team concluded that LK-99 is not a superconductor but an insulator with a resistance too high to run a standard conductivity test.

Epilogue

It was not the first time superconductors have triggered ripples of excitement. 

Copper oxide high-temperature superconductors were first discovered in 1986 by physicists J. Georg Bednorz and K. Alex Müller. The Nobel Prize in Physics was awarded for this important breakthrough in the following year. 

Four decades later, the debate still goes on over the materials' superconducting mechanism.

"Realizing superconductivity at room temperature and ambient pressure is of great significance because it could greatly change people's daily lives," Luo told CGTN.

Its application scenarios extend to medical treatment, quantum computing and maglev trains, and it's a crucial solution to energy shortage. 

While the exploration of room-temperature superconductors at ambient pressure has not yet made much progress around the world, there have been significant developments under high pressure, according to Luo.

Read more: No other results confirm LK-99 superconductor claim: Chinese researcher