Explained | Why a floating speck of metal sent scientists' hearts racing

The past three weeks have witnessed the dramatic rise and fall of a new candidate for the holy grail of materials science: a superconductor that works at room temperature. On July 22, a team of researchers in South Korea reported their findings on a compound they called LK-99, claiming that its discovery was a “brand new historical moment” that would “open a new era for mankind.” A boisterous frenzy of online physics discussions and rapid-fire publications followed, only to fall flat two weeks later. LK-99, it seemed, was a bust.

The public interest around LK-99 was a social phenomenon as much as a scientific one. The sheer volume of online discussions on message boards, group chats, Reddit and X, the app formerly known as Twitter, brought the attention of research scientists who began running simulations and experiments to replicate or refute the Korean team’s claims. For a brief moment, a large audience of people new to superconductivity found sudden fascination with a niche area of materials science, seeking an answer to a rarely heard yet profound question: Had humanity just entered a new golden age?

Whenever electrical power runs through a transmission line, some is lost as waste heat, an omnipresent tax imposed by the laws of nature. The miraculous potential of superconductors is that they carry electricity over large distances with perfect efficiency. If we ever figure out how to manufacture them cheaply and make them work at room temperature rather than only at hundreds of degrees below zero, it would revolutionize our economy and help save the environment. Superconductors can also achieve feats like powerful magnetic fields and levitation in midair, enabling new categories of electronic devices, computers and modes of transportation.

Unfortunately, the highest temperature material currently known to superconduct only does so at -10 degrees while needing to be put under a pressure of around 1.9 million atmospheres. Materials that superconduct at ambient pressure require temperatures below roughly -150 degrees, limiting their use to applications where the cryogenic engineering is worth it, like medical imaging and experimental physics.

These properties are made possible in superconductors by the way electrons move differently through them than they do through common metals. In copper and other electrically conductive materials, imagine a ball of electrical current dropped into the top of a Plinko machine, bouncing on pegs all the way down. Each bounce transfers a bit of energy from the ball to a peg — that’s the heat tax at work. In a superconductor, the balls of electrical current glide smoothly, like marbles along a track. No heat, no lost energy.

An eco-friendly electrical grid

Room-temperature superconductors would have the greatest impact on energy generation, transmission and distribution. Currently, 8 percent to 15 percent of all energy produced for electrical grids is lost as waste heat en route to being used. In the United States, this adds up to dozens of nuclear power plants worth of wasted power. Using room-temperature superconductors in electrical transformers, which lower high voltages in transmission lines to levels appropriate for home use, and generators, which convert rotational energy into electrical power, could save another 30 percent to 40 percent of wasted power while reducing the amount and complexity of materials it takes to make such equipment in the first place.

Superconducting transmission lines would also enable near lossless transfer of renewable energy over vast distances. Power generated by massive solar arrays in the West Coast deserts could more easily fuel East Coast cities throughout the winter, and superconductor-based energy storage could replace industrial-scale batteries entirely, solving one of the main challenges in developing renewable energy at scale. These storage systems work by letting electrical current travel in an endless loop, and since it does so with virtually no losses, it can continue circling this loop with very little power used to keep it going. The total energy lost when charging and discharging a conventional battery is around 20 percent, while in such a superconducting storage system, it would be closer to 5 percent.

Better, cheaper M.R.I.s

Low-temperature superconductors are used today in applications requiring powerful magnetic fields, such as M.R.I. machines. A significant contributor to the expense of those machines is the liquid helium needed to cool the magnets down to cryogenic temperatures. Each M.R.I. machine requires about 500 gallons of helium to operate, and the limited, fluctuating supply prices of helium can drive up the price and limit the availability of M.R.I.s to patients in need.

The resolution limit of M.R.I. scans is determined by the strength of the magnetic field, and superconductors can produce very strong magnetic fields. Cheaper machines that operate without cryogenic cooling have been proposed, but they would have a much lower resolution without superconductors, limiting their ability to detect small but important health conditions. Room-temperature superconductors would solve both of these challenges. Cheaper, more accessible, and higher resolution, noninvasive medical imaging could transform the quality of diagnostic medical care — particularly in poorer countries that have less access to M.R.I.s today.

High-speed public transit

High-strength magnetic fields produced by superconductors can also be used commercially to levitate high-speed trains on a thin cushion of air above the tracks. This technology has been in development in Japan for decades, with maglev trains originally projected to open to the public in 2027, running at speeds up to 375 miles per hour between Tokyo and Nagoya. In the United States, a maglev train line has recently been proposed to carry commuters between New York City and Washington, DC, in under an hour.

These specialized trains are incredibly costly to build and difficult to engineer because of our current superconducting materials, limiting their application to only the world’s busiest and densest commuter corridors. Room-temperature superconductors would drastically simplify the design and engineering of high-speed trains, reaching speeds that would make rail competitive with airlines for continental intercity travel. As a bonus, these trains could run off clean, superconductor-enabled grid energy, eliminating the thousands of pounds of carbon dioxide emitted to carry the passengers on a domestic flight.

High-efficiency computer chips

The transistors that power all modern electronics have limitations: They can only operate so fast, and every operation loses energy as heat. The speed of transistor operations of computer chips steadily increased until the mid-2010s, when it reached the material limits of our current silicon-based transistors. The density of transistors in a modern computer chip is also heavily limited by our ability to remove waste heat, which is why chips are small, flat rectangles, often with large heat sinks attached to the top, instead of solid cubes.

Computer chips designed with superconducting materials have the potential to be around 300 times as energy efficient and 10 times as fast as our current silicon-based microelectronics. Eliminating waste heat would enable more compact designs, longer battery lives and a lower tax on our electrical grid to power the digital economy. Finally, we could leave as many browser tabs open as we want.

Fusion energy

The most exciting role room-temperature superconductors might play in our future economy is in the production of cheap, clean energy. The recent emergence of privately funded nuclear fusion projects has largely been enabled by advances in manufacturing high-temperature superconducting tape, which generates the extremely powerful magnetic fields that trap and confine a hot, charged gas called plasma at over 180 million degrees. A room-temperature superconductor made of widely available cheap metals would dramatically accelerate the timeline to replace our most dangerous and polluting forms of energy — coal and oil — with fusion energy, which works by the same principle that powers the sun.

Fusion energy, if it ever arrives, is said to be the last power source humanity will ever need. Since the fuel for fusion can be extracted from seawater, it would free our energy supplies from the geopolitical turmoil that sends shocks to our economy from time to time through the oscillating prices of oil and natural gas. For a sense of scale, the hydrogen from one gallon of seawater, when burned in a fusion reactor, releases approximately the same amount of energy as over 1,000 gallons of refined gasoline. Unlimited, conflict-free, carbon-free energy would reduce the cost of almost every part or product, since half the price of common materials like steel and aluminum is the cost of the electricity it takes to make them.

Our central dilemma in the modern, environmentally conscious world is that we must learn to do more with less. The engine of our economy demands constant growth to sustain itself. Yet we also recognize the need to reduce our impact on the world around us and protect the ailing environment. Our incentives and obligations to the material world are pulling us in different directions. The allure of a room-temperature superconductor grows as our economic and environmental picture darkens. It’s the kind of miracle material that could slow climate change while supercharging global economic prosperity, realized through new technologies previously only seen in science fiction.

In recent days scientists have published several new reports showing that LK-99 is not a superconductor at room temperature but rather a fairly mundane magnetic substance that mimics some of the visual properties characteristic of superconductors, like levitating over a strong magnet, but not the most important physical property of zero electrical resistance. Rather than striking gold, the Korean scientists probably discovered a new form of pyrite.

We still don’t know whether the field of superconductivity research will benefit from the new avenues opened up in the last few weeks if many labs continue to investigate materials similar to LK-99. It’s a field where theory and experiment have often challenged each other, and our expectations of what is possible have frequently been questioned by what has been observed. Although public interest will no doubt fade for now, a bold promise remains: a superconducting golden age might be just over the horizon, and the role of science is clear — to find a way to get us there.