Real or not? What to know about new 'superconductor' claim

The Korean scientists behind LK-99 claim they've developed a new room-temperature, ambient-pressure superconductor called PCPOSOS. Doubts linger over the validity of their research.

A superconductor during an experiment at low temperature at the Korea Basic Science Institute in Daejeon. [KIM SUNG-TAE]

The Korean scientists behind the viral, debunked superconductor LK-99 that swept the scientific community last year is going for a second run with PCPOSOS — a new material they insist exhibits superconductivity in room temperature and ambient pressure.

Is the second time the charm? Not according to the scientific community — or the stock market.

The research group asserted in a preprint last July that its newly created LK-99 — a compound of lead, copper, phosphorous and oxygen — was the world's first room-temperature, ambient-pressure superconductor.

The study created a frenzy across the globe. A material capable of conducting electricity with zero resistance in room temperature and ambient pressure has long been considered a holy grail in science and technology circles. If created, such a compound could theoretically conduct power without losing any energy, bringing fundamental changes to every aspect of electricity.

The group's ambitious claims, however, were soon debunked by scientists and scientific societies around the world, including the Korean Society of Superconductivity and Cryogenics, after attempts to replicate the findings were unsuccessful.

Below are some frequently asked questions and answers based on the Korea JoongAng Daily's reporting on the superconductor frenzy and the scientists behind it.

Who are the scientists behind the superconductor claim?

All five them are Korean, and four out of the five are affiliated with a Seoul-based private company called Quantum Energy Research Centre. Although their claims about superconductive materials have been subject to skepticism, the Korea JoongAng Daily found no major forgery in their academic backgrounds.

Kim Hyun-tak, the lead author and presenter of the latest research, serves as a research professor of physics at the College of William & Mary in the United States. Kim is the only member who is not tied to the Quantum Energy Research Centre.

Kim holds a bachelor's degree in physics from Pusan National University and earned a master’s degree from Seoul National University. Kim became established as a researcher in superconductivity while working on his doctoral degree at Japan's University of Tsukuba, where he wrote his dissertation on low-temperature superconductors. Prior to his post at William & Mary, he worked at Electronics and Telecommunications Research Institute in Korea.

Lee Suk-bae, the head of the Quantum Energy Research Centre, is the lead author of the LK-99 manuscript and the second author of the latest research. He holds bachelor's and master's degrees in chemistry, as well as a doctorate in microelectronics from Korea University, where his dissertation presented a theoretical examination of Gallium-linked polyphosphazene as a potential superconducting material.

Lee and other authors who attended Korea University are largely influenced by Chair Tong-seek, a professor emeritus of chemistry at the institution.

How is PCPOSOS different from LK-99?

The key difference between LK-99’s chemical formula — Pb10−xCux (PO4) 6O — and that of PCPOSOS — Pb10-xCux (P (O1-ySy) 4) 6O1-zSz — is the addition of sulfur, which partially substitutes oxygen atoms.

Academic circles, however, found the data on PCPOSOS provided during Kim's presentation at the American Physical Society on Monday to be largely similar to those which were presented for LK-99.

Kim said on that occasion that the team would publish a manuscript explaining how said material was synthesized to demonstrate the formula in detail on the preprint site arXiv that day, but no manuscript on PCPOSOS submitted by Kim, Lee or any of the team members could be retrieved on the website as of Wednesday.

A slide displaying measurements of the electric resistance of PCPOSOS, which a group of Korean scientists claims is a room-temperature, ambient-pressure superconductor, shown during a presentation by Kim Hyun-tak, a physics professor at the College of William and Mary, at the American Physical Society meeting in Minneapolis, Minnesota on Monday. [SCREEN CAPTURE]

What kind of data have been presented by the PCPOSOS team, and what are its shortcomings?

To qualify as a superconductor, a material should exhibit zero electric resistance as well as full levitation on the magnetic field in the superconducting state.

The Korean team claims that PCPOSOS displays characteristics of a Type-II superconductor, including partial levitation when placed on a magnet and near-zero resistance at room temperature.

The team claims that Jung Dae-chel of the Superconductor Technology Lab has replicated its findings.

Nevertheless, because Kim did not present a physical sample of the material during the APS meeting, several questions remain regarding its scientific validity.

Type I superconductors, which are typically pure metals, exhibit perfect repulsion from magnets and abruptly lose superconductivity when the magnetic field gets too strong. Type II superconductors, on the other hand, may enter a mixed state where the magnetic field starts to partially leak in.

If PCPOSOS is a Type II superconductor, it should exhibit full levitation. Kim did present an image of PCPOSOS fully levitating on a magnet, magnified 1,600 times. But the scale of that levitation is extremely small, and the reproducibility and validity of the experiment remain questionable because a physical sample has not yet been presented.

Moreover, Kim's presentation showed electric resistance ranging from 10⁻² to 10⁻⁴ Ω at around 25 degrees Celsius. While measuring the metric at absolute zero can be logistically difficult, this fact is a major confound to the team's data, and means that PCPOSOS has not shown a dramatic drop in resistance near absolute zero.

BY SHIN HA-NEE, PARK EUN-JEE [shin.hanee@joongang.co.kr]