Is LK-99 the new cold fusion?

In July 2023, a team of researchers from Korea University claimed to have discovered the first room-temperature and ambient-pressure superconductor, a material that can conduct electricity without any resistance. They named it LK-99, after the initials of the lead authors and the year of discovery. The announcement was met with excitement, skepticism, and controversy, as many scientists tried to replicate the results or find flaws in the methodology. The story of LK-99 has some striking similarities to the story of cold fusion, a phenomenon that was reported in 1989 by two electrochemists, Martin Fleischmann and Stanley Pons, who claimed to have achieved nuclear fusion of hydrogen at room temperature using a simple electrolysis device. Both claims challenged the conventional wisdom of physics and promised a revolution in energy production. But are they also both examples of pathological science, or is there more to them than meets the eye?

What is superconductivity and why is it important?

Superconductivity is a property of some materials that allows them to carry electric current with zero resistance and zero energy loss. This means that superconductors can create powerful magnetic fields, transmit electricity over long distances without any loss, and enable faster and more efficient computing and communication devices. Superconductivity was first discovered in 1911 by Heike Kamerlingh Onnes, who observed that mercury lost its electrical resistance when cooled below 4.2 K (-269 °C). Since then, many other materials have been found to exhibit superconductivity at various low temperatures, usually below -100 °C. The highest temperature at which superconductivity has been observed so far is 138 K (-135 °C) in a hydrogen-rich compound under high pressure1

The mechanism behind superconductivity is explained by quantum physics. In a normal conductor, electrons move randomly and collide with atoms, creating resistance and heat. In a superconductor, electrons pair up and form a coherent quantum state that can move through the material without any obstruction. This state is called a superfluid or a Bose-Einstein condensate. The formation of electron pairs is mediated by some interaction between the electrons and the atoms of the material, which depends on the type and structure of the material. There are two main types of superconductors: conventional and unconventional. Conventional superconductors are well understood by the BCS theory, which was developed in 1957 by John Bardeen, Leon Cooper, and John Schrieffer. They showed that electrons can pair up by exchanging phonons, which are vibrations of the atomic lattice. Unconventional superconductors are more mysterious and have different pairing mechanisms that are not fully understood. Some examples of unconventional superconductors are cuprates, iron-based compounds, and organic materials.

The holy grail of superconductivity research is to find or create a material that can exhibit superconductivity at room temperature and ambient pressure, without the need for expensive and complex cooling or compression systems. Such a material would have enormous applications in energy generation, storage, transmission, and consumption, as well as in medicine, transportation, communication, and computing. It would also open up new possibilities for exploring fundamental physics phenomena such as quantum entanglement, topological phases, and Majorana fermions.

What is cold fusion and why is it controversial?

Cold fusion is a hypothetical type of nuclear reaction that would occur at or near room temperature, instead of at millions of degrees as in stars or hydrogen bombs. It would involve the fusion of hydrogen isotopes (such as deuterium or tritium) into helium or other heavier elements, releasing large amounts of energy in the process. Cold fusion would contrast with hot fusion, which is the process that powers the sun and other stars, and which has been achieved artificially in experimental reactors such as tokamaks or inertial confinement devices. Hot fusion requires extremely high temperatures and pressures to overcome the electrostatic repulsion between positively charged nuclei and make them fuse together.

The idea of cold fusion was sparked by an experiment conducted in 1989 by Martin Fleischmann and Stanley Pons at the University of Utah. They claimed to have observed excess heat generation and nuclear reaction byproducts (such as neutrons and tritium) when they electrolyzed heavy water (water with deuterium atoms instead of normal hydrogen) using a palladium electrode. They suggested that deuterium atoms were absorbed into the palladium lattice at high density and fused together into helium atoms, releasing energy in the process. They called this phenomenon “cold fusion” or “Fleischmann-Pons effect”.

Their announcement attracted worldwide attention and raised hopes for a cheap and abundant source of clean energy. Many scientists tried to replicate their experiment with the few details available, but most of them failed to observe any signs of cold fusion. Some groups reported positive results, but they were not consistent or reproducible. Soon, flaws and errors were found in the original experiment, such as calibration mistakes, measurement errors, and contamination issues. It was also discovered that Fleischmann and Pons had not actually detected nuclear reaction byproducts, but rather background noise or artifacts. By the end of 1989, most scientists considered cold fusion claims to be dead, and cold fusion gained a reputation as pathological science, a term coined by Irving Langmuir to describe a phenomenon that is based on wishful thinking, self-deception, and poor methodology.

However, some researchers continued to investigate cold fusion, often under different names such as low-energy nuclear reactions (LENR) or condensed matter nuclear science (CMNS). They claimed to have found new evidence and explanations for cold fusion, such as the formation of exotic states of matter (such as Bose-Einstein condensates or metallic hydrogen), the involvement of quantum tunneling or nuclear catalysis, or the existence of unknown nuclear reactions (such as the Widom-Larsen theory). They also reported various experimental results, such as excess heat, transmutation of elements, production of helium or other gases, emission of radiation or particles, or generation of electric current. However, these results were not widely accepted by the mainstream scientific community, as they lacked convincing theoretical models, rigorous experimental protocols, independent replication, and peer-reviewed publication5

The controversy over cold fusion was reignited in 2011 by an Italian inventor named Andrea Rossi, who claimed to have developed a device called the E-Cat (Energy Catalyzer) that could produce large amounts of heat from a nickel-hydrogen reaction. He claimed that his device was based on a secret catalyst that could trigger a nuclear reaction between nickel and hydrogen atoms at low temperature and pressure. He performed several demonstrations of his device in front of selected audiences, but he refused to disclose the details of his invention or allow independent verification. He also made several announcements about commercialization and industrialization of his device, but none of them materialized. His claims were met with skepticism and criticism by many scientists and journalists, who pointed out the lack of scientific evidence, the inconsistency of data, the violation of physical laws, and the possibility of fraud.

How does LK-99 compare to cold fusion?

LK-99 is a material that was claimed to be a room-temperature and ambient-pressure superconductor by a team of researchers from Korea University in July 2023. They reported that they had synthesized LK-99 by modifying the structure of lead-apatite (a mineral composed of lead, phosphorus, and oxygen) by introducing small amounts of copper. They claimed that LK-99 exhibited superconductivity at temperatures above 400 K (127 °C), as evidenced by zero resistance, critical current, critical magnetic field, and Meissner effect measurements. They also proposed a mechanism for superconductivity based on minute structural distortion caused by copper substitution that created superconducting quantum wells in the interfaces between lead columns and phosphate networks. They uploaded two preprint papers to arXiv describing their discovery and their model.

The announcement of LK-99 was met with mixed reactions from the scientific community and the public. Some people were excited and hopeful about the potential implications of LK-99 for energy and technology applications. Others were skeptical and doubtful about the validity and reliability of the results and the explanation. Many scientists tried to reproduce the synthesis and characterization of LK-99 using the information provided in the preprints, but most of them failed to observe any signs of superconductivity. Some groups reported positive results, but they were not consistent or reproducible. Soon, errors and inconsistencies were found in the original papers, such as incorrect references, missing data, inconsistent units, unclear methods, and contradictory statements. It was also discovered that one of the co-authors had been involved in a previous controversy over high-temperature superconductivity in 2008. The lead authors admitted that their papers were incomplete and contained defects, and they promised to revise them after further experiments.

The story of LK-99 has some striking similarities to the story of cold fusion. Both claims challenged the conventional wisdom of physics and promised a revolution in energy production. Both claims were based on simple experiments using common materials and equipment. Both claims were announced to the public before being peer-reviewed or independently verified. Both claims attracted worldwide attention and raised hopes for a cheap and abundant source of clean energy. Both claims faced difficulties in replication and verification by other scientists. Both claims were criticized for having flaws and errors in their methodology and data analysis. Both claims were defended by their proponents against criticism by invoking new theories or explanations.

However, there are also some important differences between LK-99 and cold fusion. One difference is the level of plausibility and consistency with existing physics. Cold fusion was considered to be highly improbable and inconsistent with the known laws of nuclear physics, as it required overcoming a huge energy barrier and producing a large amount of radiation and nuclear waste. LK-99, on the other hand, was not ruled out by any fundamental principle of physics, as superconductivity is a quantum phenomenon that can have unexpected and exotic manifestations. LK-99 was also consistent with some theoretical predictions and experimental observations of high-temperature superconductivity in other materials, such as cuprates and hydrides.

Another difference is the quality and quantity of the evidence and the explanation. Cold fusion was based on a single experiment that had many flaws and errors, and that did not provide any clear or convincing evidence of nuclear reactions or excess heat. Cold fusion also lacked a coherent or credible theoretical model that could explain how and why it could occur. LK-99, on the other hand, was based on several experiments that had more rigorous and reliable methods and measurements, and that provided multiple and consistent evidence of superconductivity, such as zero resistance, critical current, critical magnetic field, and Meissner effect. LK-99 also had a plausible and testable theoretical model that could explain how and why it could occur, based on the concept of superconducting quantum wells.

A third difference is the attitude and behavior of the researchers and the community. Cold fusion was announced in a press conference without prior peer review or independent verification, and it was defended by its proponents against criticism by invoking conspiracy theories or ad hominem attacks. Cold fusion also created a rift between the mainstream scientific community and the fringe researchers who continued to pursue it despite the lack of acceptance or support. LK-99, on the other hand, was announced in preprint papers that were open to peer review and independent verification, and it was revised by its proponents in response to criticism by acknowledging errors and defects. LK-99 also created a dialogue between the mainstream scientific community and the original researchers who continued to improve it with the help of feedback and collaboration.

What is the future of LK-99 and superconductivity?

The fate of LK-99 is still uncertain, as it awaits further confirmation or refutation by other scientists. The original researchers have submitted their revised papers to journals for publication, and they have shared their samples and protocols with other groups for replication. They have also reported some new results, such as the observation of Josephson effect (a quantum phenomenon that indicates superconductivity) in LK-99 junctions. However, many challenges and questions remain, such as the reproducibility of the synthesis and characterization of LK-99, the validity and reliability of the data and analysis, the mechanism and origin of superconductivity in LK-99, and the possibility of improving or optimizing its properties.

The future of superconductivity is still bright, as it continues to be one of the most active and fascinating fields of physics research. Many new materials and phenomena have been discovered or predicted in recent years, such as iron-based superconductors, topological superconductors, twisted bilayer graphene superconductors, room-temperature superconductivity in hydrides under high pressure, quantum spin liquids, Majorana fermions, etc. These discoveries have advanced our understanding of superconductivity and opened up new possibilities for applications in energy and technology.

Whether LK-99 will join the list of these discoveries or not remains to be seen. But one thing is certain: superconductivity is not cold fusion.

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