Bowdoin Science Journal

A Swing and a Miss

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In July 2023, a revolutionary preprint paper was published. Researchers at the Quantum Energy Research Center in Seoul, South Korea claimed to have synthesized a material, LK-99, that is a superconductor at room temperature (TC ≥ 400 K) and ambient pressure. They believed that this discovery would be a “brand-new historical event that opens a new era for humankind” (Lee, 2023). Given that all superconductors developed so far operate only under very high pressures or very low temperatures, this indeed would have been a game changer. However, as of November 2023, repeated unsuccessful attempts to reproduce the superconductive property in this material have added this study to a growing list of apocryphal claims in scientific literature.

What is a superconductor?

A superconductor is a material that allows current to flow through it without any resistance. For example, think of a toaster. The exposed wires in a toaster are typically made of a nickel-chromium alloy, which has a high resistance. As the electrons flow through the wires, they collide with the atoms of the wires and generate heat, enough to toast your bread. Superconductors, however, allow electricity to pass through without any resistance. A superconductor toaster then, would not generate any heat and leave the bread cold.

Naturally, a straightforward method to determine if a material has superconductive properties is by measuring whether the resistance of a current flowing through it falls to zero. This phenomenon usually occurs at a specific temperature known as the “critical temperature”, which varies for different materials.

Another unique property of superconductors is quantum levitation. The Meissner effect causes a superconductor to expel incoming magnetic fields by producing small currents on the surface of the material. The magnetic force is strong enough to counter gravity and push the superconductor up. However, in type-1 superconductors, the complete lack of magnetic fields inside the material would lead to an unstable wobbly floating if it were placed on top of a flat magnet. In type-II superconductors, flux tubes or tunnels can form through the superconductor and effectively lock the material in place above a magnet. This levitation, combining the principles of the Meissner effect and flux pinning, creates what can be described as a seemingly magical phenomenon, where a superconductor floats effortlessly above a magnetic source. (Hellman et al., 1988) (Murakami et al., 2018).

Credit: Simran Buttar

Credit: Mai-Linh Doan/Wikimedia Commons

Debunking LK-99

LK-99 is a polycrystalline structure made of lead, oxygen, and phosphorus and is infused with copper. The report on LK-99 indicated a sharp decrease in resistivity at around 104 C, the supposed critical temperature for that material. Jain explains this apparent superconductive effect in his preprint to be the result of a phase transition of copper (I) sulfide at around 104 C, which caused the sudden change in electrical resistivity (Jain, 2023). He explains that this sudden drop likely led the Korean researchers to believe that they had reached the critical temperature.

To further disqualify the study, researchers at Peking University observed a “half-levitation”, a phenomenon that exhibits within ferromagnetic insulators but is not the kind of diamagnetic levitation resulting from the Meissner effect in superconductors. This was observed in videos of the LK-99 made in Korea as well as in the Chinese teams’ recreation of the material and testing of its Meissner effect (Guo et al., 2023).

Other studies have shown that LK-99 is not a feasible superconductor through theoretical methods (Jiang et al., 2023), while other studies have recreated the material but not the superconductive properties at room temperatures (Puphal et al., 2023). The accumulating evidence places LK-99 firmly in the realm of improbable scientific breakthroughs, casting doubt on its viability as a room-temperature superconductor.

Behind the Controversy

The drama began with Korea University professor Young-Wan Kwon’s rapid publishment of the significant paper. Shortly after, the rest of the team published a similar paper, notably without Kwon as a co-author. There was reportedly a clash between Kwon and the author of the second paper, Suk-Bae Lee. One popular rumor explaining the hurried first paper is that Kwon was afraid he would not receive the Nobel Prize, an award that can only be shared by up to three individuals.

Shortly after the publication, Kwon was confirmed to have been removed from the Quantum Energy Research Centre. Although much of the story is shrouded in mystery, an investigation into the case was begun by Korea University and is expected to shed light on the details of the case. The results of this inquiry are expected to conclude by early next year and will hopefully unravel the complexities of this controversy.

Superconductors now and in the future

Superconductors have already found significant applications in today’s world, particularly in the field of medical technology. Many MRI machines, for example, depend on superconducting wires to create the strong magnetic fields necessary for producing detailed body scans used in medical diagnostics and imaging (Parizh et al., 2017, Manso Jimeno et al., 2023). Similarly, superconductors are used in the Superconducting Quantum Interference Device (SQUID), which allows for extremely sensitive detection of magnetic fields, thus allowing for precise imaging of the brain. Such advancements could revolutionize neuroscience studies, offering insights into brain function and aiding in the development of neurological treatments (Fagaly, 2006).

Superconductors can also be found in transportation systems such as the Maglev, magnetically levitating trains that can travel over 300 mph. Materials with the touted properties of LK-99 could potentially eliminate the need for expensive and environmentally taxing cryogenic cooling systems currently necessary for such levitating trains (Biswas & Biswas, 2023) Generally, reducing the cost and increasing the efficiency of producing superconductors will accelerate advancements in numerous other technologies, like fusion energy and particle colliders, that rely on high-temperature superconductors. (Castelvecchi, 2023).

The enthusiasm surrounding groundbreaking technologies such as room-temperature superconductors is indeed thrilling, but it appears LK-99 won’t be at the forefront of this innovation. As the scientific community continues to explore alternative materials and methods, the dream of a room-temperature superconductor remains an elusive goal. In the meantime, the case of LK-99 serves as a valuable lesson in the cautious optimism required in technological breakthroughs.

 

References 

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