Claimed superconductor LK-99 is an online sensation — but replication efforts fall short

The assertion by a South Korean team regarding a room-temperature superconductor has gained viral attention. However, skepticism remains among the scientific community, prompting determined efforts to replicate the discovery.

The pronouncement by a South Korean research group that they have identified a superconductor capable of functioning at room temperature and under regular pressure has ignited a sensation across online platforms. This assertion has motivated both scientists and enthusiasts to embark on various initiatives to reproduce the findings. Nonetheless, initial endeavors to validate this attention-commanding breakthrough, through both experimental trials and theoretical analyses, have encountered impediments, leading researchers to harbor significant doubts.

The team, led by Sukbae Lee and Ji-Hoon Kim at Quantum Energy Research Centre, a start-up based in Seoul, disclosed preprints on July 25th. These documents proposed that LK-99, a composite comprised of copper, lead, phosphorus, and oxygen, can exhibit superconductivity at temperatures surpassing 127 °C (400 Kelvin) while existing under typical pressure conditions. The foundation of this claim rests on the manifestation of two crucial hallmarks of superconductivity: zero electrical resistance and the Meissner effect. The latter phenomenon involves the material expelling magnetic fields, causing samples to levitate when brought near a magnet. Until now, the achievement of superconductivity has primarily been confined to specific materials subjected to extremely low temperatures or exceptionally high pressures. No material has been confirmed as a superconductor under everyday conditions.

LK-99's purported superconducting qualities have attracted scrutiny within the scientific community. Inna Vishik, a condensed matter experimentalist at the University of California, Davis, remarked, "These 'Unidentified Superconducting Objects,' as they are sometimes referred to, frequently appear on the arXiv. It seems a new one emerges every year or so." While advancements in superconductivity often spark speculation about their potential impact on technologies like computer chips and maglev trains, Vishik cautioned against excessive optimism. While progress in superconductivity has greatly enriched fundamental scientific understanding, practical applications have historically been limited. Achieving room-temperature superconductivity does not guarantee immediate practical utility.

Initial attempts to replicate LK-99, as recently reported, have not yielded conclusive results. None of these studies have provided unequivocal evidence of superconductivity in the material.

Separate experimental efforts by the National Physical Laboratory of India in New Delhi and Beihang University in Beijing succeeded in synthesizing LK-99. However, neither team observed signs of superconductivity. Another experiment conducted by researchers at Southeast University in Nanjing detected no Meissner effect but did measure nearly zero resistance in LK-99 at -163 °C (110 K), a temperature well below room temperature yet relatively high for superconductors.

Theoretical studies have also entered the discourse. Several theoretical analyses have employed density functional theory (DFT) to explore LK-99's electronic structure. These calculations suggested that LK-99 might possess intriguing electronic features often linked to behaviors such as ferromagnetism and superconductivity. Nevertheless, none of these studies have identified compelling evidence confirming LK-99's superconductivity under ambient conditions.

The journey to demystify LK-99's properties faces significant challenges due to the uncertainty surrounding its structure. Theoretical studies rely on specific structural assumptions for computational purposes, a constraint dictated by incomplete knowledge of the material's true configuration.

Although a theoretical analysis posted on Twitter by Sinéad Griffin, a researcher at Lawrence Berkeley National Laboratory, initially generated enthusiasm online, Griffin later clarified that her work did not constitute proof or evidence of superconductivity. Other theoretical papers also proposed the existence of 'flat bands,' yet these studies are all grounded in assumptions about the material's structure, a limitation that curtails the conclusiveness of their findings.

The absence of unequivocal success in replicating the results has not quelled speculation on the internet. Videos claiming to show samples levitating due to superconductivity have circulated widely. However, such occurrences can be simulated by various materials, including graphene, frogs, and pliers, often creating misleading impressions. Previous claims of room-temperature superconductivity, such as the one made by physicist Ranga Dias in March, have garnered attention. Nevertheless, the viral fervor surrounding LK-99 has eclipsed that of its predecessors.

In the midst of this atmosphere of hype, some scientists have adopted a satirical approach, mimicking levitation videos using everyday materials suspended by strings and other means. Eric Aspling, a physicist at Binghamton University, shared a video featuring a "sample of LK-99 shaped as a fork" suspended by tape. Aspling expressed skepticism regarding the persuasiveness of such videos.