LK

Nov 25, 2023

Experts continue to push back against extraordinary claims of a room-temperature superconductor. But even a flop could open up new pathways for materials research.

When South Korean scientists reported a potential breakthrough in superconductors in late July, their claims uncorked waves of excitement and skepticism as researchers around the world rushed to replicate the experiments.

Such a superconductor — transmitting electricity with no energy loss at room temperature and ordinary air pressure — is a holy grail of materials science. Dreamers hope for room-temperature superconductors that could maximize the efficiency of our energy grids and supercharge fusion energy production; speed up progress on quantum computers; or help usher in an era of superfast transport.

In the weeks since that first report, though, the story of the LK-99 superconductor has been all about what's going on in laboratories — which pretty quickly brought the hype down to earth. Efforts at replication and confirmation have supported the skeptics and have provided more clarity about what LK-99 is and what it isn't.

On July 22, the physicists in South Korea uploaded two papers to arXiv, a repository for preprint research — the kind that has yet to be peer-reviewed and published in a scientific journal. It's basically like uploading a first draft of your work. The researchers claimed they'd produced the first room-temperature superconductor with a "modified lead-apatite structure" doped with copper and dubbed LK-99.

Part of the "proof" the team provided was a video showing the compound levitating over a magnet, a key characteristic of superconducting materials.

The bold claims made a monumental splash with experts in the field.

"The chemicals are so cheap and not hard to make," said Xiaolin Wang, a material scientist at the University of Wollongong in Australia. "This is why it is like a nuclear bomb in the community."

But what happened in that lab in South Korea was just a very first step in figuring out whether the results might somehow have practical implications for technology and its role in our lives. We needed more data, and from the start there was reason to be cautious.

A bona fide room-temperature superconductor would be a big deal worthy of fanfare. Modern materials we use to conduct electricity, like the copper wiring supplying energy to your home, are inefficient. As electrons bumble down the wire, they bump into the atoms of the material, creating heat and losing energy. This is known as electrical resistance, the reason up to 10% of electricity is wasted as it travels through transmission lines to homes. Energy loss happens in our electronic devices as well.

But if wires and transmission lines were to be made from a superconductive material, you could practically negate those losses. The electrons form pairs as they travel through the material and don't bump into the atoms so much, enabling them to flow freely.

Superconductive materials already exist and are in use in various applications, like MRI machines, around the world. However, these require extremely low temperatures (approaching absolute zero at around minus 459 degrees Fahrenheit) or extremely high pressures (beyond 100,000 times the atmospheric pressure).

Meanwhile, a superconducting magnetic levitation system is being built by Central Japan Railway to take passengers between Tokyo and Nagoya. The SCMaglev train uses rubber wheels to get up to speeds of around 93 miles per hour before the superconducting magnetic system takes over. It should be able to reach speeds of 311 mph.

The process requires a superconducting niobium-titanium alloy, which is cooled to minus 452 degrees Fahrenheit with liquid helium.

A room-temperature superconductor like LK-99 would make this a far cheaper endeavor and mean there's no need to accumulate helium. (Contrary to some concerns in the media over the last few years, we're not running out of helium anytime soon, but it's produced in only a few countries, so problems with supply can cause massive price spikes.)

From the get-go, Wang and other superconductivity experts were skeptical about the original LK-99 experiment, pointing out inconsistencies in the data. He said the results shouldn't be hyped "until more convincing experimental data are provided." His team at the University of Wollongong began working on replicating the results, but it had trouble with sample fabrication.

In an interview with Science magazine published July 27, Michael Norman, a physicist at Argonne National Laboratory, was blunt. He said the South Korean team "come off as real amateurs."

By early August, attempts to follow the recipe and confirm LK superconductivity mostly had failed. Monitoring the surge of new superconductivity experiments by various labs and individuals became something of a cottage industry.

Across X, the social network formerly known as Twitter, LK-99 trended for days. It officially crossed over into Meme Territory — everyone's talking about "floaty rocks" — and generated some outlandish claims, with many people noticing the abundance of accounts quickly morphing from promoting AI investments to suddenly backing stocks in superconductors. The American Superconductor Corporation's shares doubled immediately after July 27 but quickly came back down to their earlier levels.

Even the CEO of ChatGPT-maker OpenAI, Sam Altman, weighed in, joking, "love these emails from recruiters asking for 2+ years of experience with lk-99."

The skepticism around LK-99 is well founded. Over the years, many teams have claimed to discover room-temperature superconductors. Most of these claims haven't withstood scientific scrutiny.

For instance, in 2020, a team led by Ranga Dias, a physicist at the University of Rochester in New York, published evidence of a room-temperature superconductor, in the prestigious journal Nature. The article was retracted in September 2022 after questions were raised about the manner in which the data in the paper was processed and analyzed. The authors maintain the raw data provides strong support for their claims, but replication of their experiment hasn't been achieved.

So what does LK-99 mean for you? At this very moment, probably not a lot, unless you want to fall down a physics rabbit hole on X and get caught up in the moment. In the near future, maybe not a lot, either.

Replicating the LK-99 experiments has largely proved a bust. Two studies conducted by two separate research groups and posted to arXiv on July 31 weren't able to replicate the South Korean research. Some of the superconductivity behaviors of the material were seen in very tiny samples by Chinese researchers, Wang noted.

With excitement at a fever pitch at that point, theoretical studies rushed to try to explain LK-99's characteristics.

Sinéad Griffin, a physicist at the Lawrence Berkeley National Laboratory, provided some analysis of LK-99's abilities using supercomputer simulations. (Griffin's post on X was accompanied by a meme of Barack Obama dropping the mic.) This study was also posted to arXiv as a preprint.

Physicists who weighed in on Griffin's work were cynical about the mic-drop reference and weren't convinced it provided any solid proof for superconductivity. Griffin herself clarified her results in an X thread, saying it neither proved nor gave evidence of superconductivity in the material, but did show interesting structural and electronic properties that have features in common with high-temperature superconductors (that is, well above minus 452 degrees Fahrenheit but way, way, way below room temperature).

By mid-August, an article in the journal Nature cited mounting evidence that LK-99 isn't a superconductor, including an experiment reproducing the partial levitation using a material that's not a superconductor. It quoted Inna Vishik, a condensed-matter experimentalist at the University of California, Davis: "I think things are pretty decisively settled at this point."

Even if LK-99 itself isn't the holy grail, it may be an interesting material in its own right, opening up the possibilities to search for room-temperature superconductors in new, unexpected ways. If somehow eventually it did lead to a room-temperature superconductor, then the possibilities might really open up.

Giuseppe Tettamanzi, a senior lecturer at the University of Adelaide's school of chemical engineering, notes that for a very long time, scientists have been thinking about replacing the power grid's copper cables with superconducting cables — a switch that could provide huge energy savings. He also mentions the benefits to quantum computers and transport.

"The sky is the limit here," he said.

Watching science in action is thrilling, and the passion for LK-99 was quite a nice change on the X feed, at least for me. But science, in action, takes time, and it shouldn't jump to conclusions about world-changing ramifications. That's why the replicators' work is so important.