Bengaluru: The latest saga in the quest for a room-temperature superconductor involves obscure Korean scientists, Soviet-era information, and anonymous Twitch and bilibili livestreamers.
The search for a room-temperature superconductor has been one of the greatest quests in physics for its potential to revolutionise the way humans live, as well as industry. The uses of superconductors include levitating trains, which are considered safer and faster.
The superconductors that exist only work under high pressures and extremely low temperatures.
A superconductor free from these conditions could, for example, make electricity transmission more efficient — without any energy loss because of resistance — and aid sustainable development in a warming world.
It now appears humanity might have gotten a step closer to it, thanks to the work of two obscure Korean scientists who co-authored a paper and got into a tiff with each other.
Or maybe not.
Also Read: A room-temperature superconductor that works in low pressure, and losing Spock’s Vulcan
What did the Korean authors publish?
In the late 1990s, scientists from Korea University in Seoul, led by Sukbae Lee and Ji-Hoon Kim, were studying superconductivity, and manufactured a polycrystalline material called LK-99 (Lee-Kim 1999, the year of discovery).
It is a modified form of lead-apatite containing trace amounts of copper, approximately indicated by the formula Pb9Cu(PO4)6O.
The authors, who are now scientists at the private company Quantum Energy Research Centre in Korea, claimed in their paper that it is a room-temperature superconductor, with a critical temperature [below which a material loses all electrical resistance or becomes a superconductor] of 400K or 127°C, and ambient pressure.
In February this year, a YouTube video was posted by the Quantum Energy Research Centre that showed a thin layer of LK-99 levitating. The authors filed for a trademark for their material in April.
On 22 July, two preprints were uploaded to arXiv, a preprint server where researchers upload papers that have not (yet) been peer-reviewed, by various authors involved in the original paper, who had seemingly had a disagreement.
Some authors also alleged that the original paper was lacking in necessary details and data, and was uploaded without permission from the other authors.
The next day, the findings of the original paper were submitted to the journal APL Materials for peer review.
The review is expected to take another 2 to 4 weeks.
A chain reaction
As soon as the preprints were uploaded in July, physicists recognised that LK-99 was relatively easy to synthesise approximately.
Immediately, both institutional scientists and independent scientists all over the world started attempting to replicate the original paper.
An anonymous Russian scientist who goes by the alias Iris Alexandra, with an anime girl avatar, started to replicate the recipe for LK-99 at home.
They are credited as having performed the first diamagnetic replication of the material, if not superconductive.
Diamagnetism is a phenomenon where materials naturally repel magnetic fields — unlike iron filings that get attracted to magnets — and this can cause confusion during superconductivity tests.
While all superconductors are diamagnetic, it isn’t true the other way round.
Some have claimed that LK-99 is based on arcane Soviet-era information that Iris and the Korean researchers had access to.
Meanwhile, two teams from China also claimed to have replicated LK-99 superconductivity, and posted their findings in the form of videos on social media and a preprint.
Multiple individuals have since gone on to attempt the replication of the material and its superconductivity, and experiments are still ongoing.
Is this confirmation of superconductivity?
No.
Any scientific phenomenon can be confirmed experimentally only if it can be replicated and also peer-reviewed. So, while there are multiple independent replication attempts, there are currently no confirmations and there has been no peer review as of 7 August 2023.
In 2020, researchers from the University of Rochester, US, had published a paper in the journal Nature about a room-temperature superconductor at a pressure of 1 million times atmospheric pressure, but the paper proved impossible to replicate and was hence withdrawn.
The same team published another paper next in the journal Physical Review Letters, but that, too, was withdrawn under suspicions of data manipulation.
What is superconductivity and why is it so exciting to scientists?
Every material that conducts electricity is a conductor with resistance and voltage. If the voltage is zero, the resistance is zero.
Superconductivity as a concept is barely a hundred years old and was discovered in 1911. It can be explained not by regular physics but by quantum mechanics. Superconductive materials are often created by mixing conductive metals.
Superconductivity is a property where, below a critical temperature, a material loses all of its electrical resistance. This means that when electricity flows through the material, there will be no loss.
Theoretically, electric current passed through a loop of a superconductive material will flow indefinitely without a power source, ie, without applying any voltage.
The temperatures needed to achieve this are typically measured in Kelvin and are currently near 75 to 100 K or (-183 to -200 °C).
The longest superconductivity experiment has had a persisting flow of electricity for the past 28 years — it’s a gravimeter in Belgium that has been causing a superconducting sphere to levitate.
Superconductive materials typically do not exhibit conduction or magnetic properties at room temperature. But, when a material is cooled and transitions from its room temperature through its critical state, to its superconducting state, it also becomes magnetic.
It expels its entire magnetic field, because of which it repels nearby magnets. This phenomenon is called the Meissner effect.
The Meissner effect is often confused for diamagnetism.
In experiments, superconductivity is typically shown by achieving levitation of the superconducting material over or under a magnet, below the critical temperature through the Meissner effect.
Why the scepticism
Many experts are still sceptical about the replication attempts, which they believe could be more likely explained by diamagnetism than the Meissner effect.
Many of the levitating LK-99 replicates seem to be similar to moderate diamagnetism as opposed to Meissner levitation or even perfect diamagnetism (called flux pinning). Some of those who’ve replicated the effect without confirming it are also not entirely clear what the material they have is or does.
The authors of the original paper provided a video to The New York Times, but that was still met with the same scepticism surrounding diamagnetism.
An academic body called the Korean Society of Superconductivity and Cryogenics (KSSC) constituted an expert committee that went on to invalidate the original paper and video.
“Based on the studies and footage, the material appearing in the research and the footage cannot be considered as a room-temperature, ambient-pressure superconductor,” they said.
The KSSC also said that it will run tests to verify superconductivity if the Quantum Energy Research Centre provides a sample of LK-99.
Quantum Energy has, meanwhile, shut down its website after it came to light that they had falsely named research institutions and companies as its partners on its site.
(Edited by Sunanda Ranjan)
Also Read: How do superconductors work? US physicist explains importance