Superconductor Claim Fail: The Rise and Fall of LK-99

In the summer of 2023, the scientific world and the internet were set ablaze by a singular claim: a team in South Korea had discovered a room-temperature superconductor. This material, dubbed LK-99, promised to revolutionize everything from energy grids to quantum computing. However, within weeks, the excitement crashed as leading laboratories worldwide debunked the findings. This article explains exactly why the claim failed, the specific impurities that fooled the researchers, and where materials science goes from here.

The LK-99 Hype: What Was Promised?

In late July 2023, a team led by Sukbae Lee and Ji-Hoon Kim from the Quantum Energy Research Centre in Seoul published two preprints on the server arXiv. They claimed to have synthesized a material—a modified lead-apatite structure doped with copper—that exhibited superconductivity at normal atmospheric pressure and temperatures up to 127°C (400 Kelvin).

The implications were massive. Standard superconductors require extreme cooling (often near absolute zero) or immense pressure to function without electrical resistance. A room-temperature ambient-pressure superconductor (RTSC) would mean:

• Lossless power grids: Eliminating the roughly 5% to 10% of energy lost during transmission.
• Cheap MRI machines: Removing the need for expensive liquid helium cooling systems.
• Levitating trains: Making Maglev technology affordable and ubiquitous.
• Efficient electronics: Computer chips that do not generate heat.

The team released a video showing a small, dark rock partially levitating above a magnet. This visual proof went viral, but physicists immediately noticed that the rock was not fully floating; one edge remained stuck to the magnet.

The Scientific Takedown: Why It Failed

The global scientific community mobilized instantly to replicate the recipe provided by Lee and Kim. Within weeks, major institutions including the Max Planck Institute for Solid State Research in Germany and Peking University in China released their findings. The verdict was unanimous: LK-99 is not a superconductor. It is actually an insulator.

The failure of the claim came down to two specific misunderstandings by the original authors:

1. The Copper Sulfide Impurity

The most damning evidence came from the Max Planck Institute. When they synthesized pure crystals of the material, they found it was a highly resistive insulator. However, the original recipe used by the South Korean team created a dirty sample containing impurities.

The primary culprit was Copper Sulfide (\(Cu_2S\)).

The original data showed a sharp drop in electrical resistivity around 104°C. The Korean team interpreted this as the “critical temperature” where the material became superconductive. In reality, Copper Sulfide undergoes a structural phase transition specifically at 104°C. At this temperature, the impurity changes its arrangement of atoms, causing a sudden drop in resistance. The researchers were measuring the properties of the impurity, not the LK-99 material itself.

2. Misinterpreting Levitation

The video of the floating rock was cited as proof of the Meissner effect. This is a phenomenon where a superconductor expels magnetic fields, causing it to lock in place or float.

However, subsequent analysis by the Center for Condensed Matter Theory at Harvard and other institutions proved that the behavior seen in the video was likely ferromagnetism or diamagnetism. The material was simply magnetic enough to be repelled by the strong magnet underneath, but not superconductive. The fact that one edge stayed on the magnet (a behavior called “flux pinning” in superconductors but also common in magnets) was actually just the heavy rock balancing on a pivot point.

Timeline of the Debunking

The speed at which the scientific community corrected the record was unprecedented, driven by social media and open-access data.

• July 22, 2023: The papers appear on arXiv.
• July 26-30, 2023: Simulation papers (including one from Lawrence Berkeley National Lab) suggest the material could theoretically have interesting electronic properties, fueling the hype.
• Early August 2023: CSIR-National Physical Laboratory in India and Beihang University in China report they synthesized the material but found no superconductivity.
• Mid-August 2023: The Max Planck Institute grows pure single crystals of LK-99. They confirm the material is an insulator and identify the Copper Sulfide phase transition as the source of the false positive.
• Late August 2023: Nature publishes a feature article summarizing the consensus: LK-99 is a bust.

The "Ranga Dias" Context

The skepticism surrounding LK-99 was heightened because the physics community was already dealing with other controversial claims. Ranga Dias, a physicist at the University of Rochester, had previously claimed to find room-temperature superconductivity in nitrogen-doped lutetium hydride under pressure.

However, those claims faced severe scrutiny. In November 2023, Nature retracted a high-profile paper by Dias due to data integrity issues. This pattern of sensational claims followed by retraction has made the field incredibly cautious. It highlights a recurring theme: measuring zero resistance is technically difficult, and experimental artifacts often look like breakthroughs.

Where The Search Goes Now

Despite the failure of LK-99, the search for room-temperature superconductors is not over. The excitement generated by the event showed just how hungry the world is for this technology. Research is currently moving in three distinct directions:

High-Pressure Hydrides

This is the most established route. Scientists have achieved superconductivity at relatively warm temperatures (near -20°C) using hydrogen-rich materials (hydrides). The catch is that these materials must be crushed between diamond anvils at pressures comparable to the center of the Earth. The goal now is to find hydrides that remain stable as the pressure is released.

AI-Driven Discovery

The failure of LK-99 highlighted the difficulty of “trial and error” chemistry. Researchers are now using Artificial Intelligence to predict crystal structures before synthesizing them. Tools like Google DeepMind’s GNoME (Graph Networks for Materials Exploration) have identified millions of new potential crystal structures, thousands of which could be stable superconductors.

Interface Superconductivity

Another avenue involves layering different materials (like graphene) at specific angles to induce superconductivity. This is known as “twistronics.” While still requiring very low temperatures currently, it offers a new playground for manipulating electron behavior without the chemical messiness of synthesizing complex ceramics like LK-99.

Frequently Asked Questions

Is there any chance LK-99 works if made differently? It is highly unlikely. The Max Planck Institute created ultra-pure crystals of the material (purple crystals) using a technique called floating zone growth. These pure crystals showed high resistance, meaning the material is an insulator, not a conductor.

What is the Meissner Effect? The Meissner Effect is the defining characteristic of a superconductor. When a material becomes superconductive, it expels all magnetic fields from its interior. This allows it to levitate perfectly stable above a magnet. LK-99 did not demonstrate this; it only showed partial levitation consistent with standard magnetism.

Why did the LK-99 researchers release the paper if it was wrong? It appears to be a case of error rather than fraud. The phase transition of Copper Sulfide at 104°C is a well-known phenomenon in geology but perhaps less obvious to researchers focused on synthesizing a new ceramic. They saw a drop in resistance and interpreted it through the lens of their desired outcome.

Are there any verified room-temperature superconductors today? No. As of late 2023 and early 2024, there are no confirmed materials that exhibit superconductivity at ambient pressure and room temperature. The record holders still require either extreme cold or extreme pressure.