If there was any hope remaining that LK-99 might be a room-temperature superconductor, it’s pretty much dead now.

In fact, it’s worse than that. Pure samples of the substance show that it is an insulator — the opposite of a superconductor. The glimmers of hope that kept the story in the news for weeks appear to be the result of impurities in the original samples.

Dozens of studies published in the last week or two have coalesced around the conclusion, less than a month after a sensational preprint paper was published by a team at the Quantum Energy Research Centre, a small company housed in the basement of a modest apartment building in Seoul, South Korea.

The Korean team made waves when it published preprints on July 22, claiming to have created a material that exhibited superconductor-like properties at ambient temperature and pressure. What’s more, the material was made of plebeian ingredients: lead, copper, phosphorus and oxygen. It flew in the face of decades of research into superconductors.

And yet it appeared to possess some of the same qualities that define superconductors. A video released by the team showed it partially levitating above a magnet, and when probing it for electrical resistance, they noticed a sharp drop around 104.8°C. Both the levitation and the resistance drop are hallmarks of superconductors.

Early warnings

There were warnings early on that the claims might be bunk. For one, the team published to a preprint server first. This isn’t necessarily a red flag, though preprints are far from the gold standard. There’s no peer review of preprints, and the bar for submission is pretty low. In most cases, that’s not a problem; preprints have allowed many fields to move more quickly than the traditional peer-review process allows, and most scientists aren’t making outlandish claims in their preprints. Still, the fact that LK-99 appeared first in a preprint wasn’t promising.