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LK-99: was there a room-temperature superconductor?

Claim · arXiv preprints, July 2023, and a very viral month

Name only. The word is real. The physics in the scene is not.

What the scene or the claim says

A copper-doped lead apatite, LK-99, superconducts above room temperature at ordinary pressure.

What is real

A superconductor carries current with zero resistance and expels magnetic fields. At ambient pressure the record stood at 133 K for three decades, in a mercury copper oxide (Hg-1223). In March 2026 Deng, Chu and colleagues reported 151 K (about −122 °C) in the same material, by a pressure-quench protocol. Room temperature is still about 140 K higher. Within weeks of the LK-99 claim, groups around the world made samples and tested them.

What stops it working that way

• None showed zero resistance or a true Meissner effect.
• The sharp resistivity drop, near 385 K (about 112 °C), was most likely a structural transition in copper(I) sulfide, an impurity left by the synthesis (Zhu et al.; Jain's analysis puts the same transition at about 104 °C). The partial "levitation" in the viral video is consistent with the material's ordinary magnetism, without any superconductivity.
• A claim like this needs three things: zero resistance, flux expulsion, and independent replication. LK-99 met none.

If you wanted it to work

Nothing in known theory forbids an ambient-pressure room-temperature superconductor, and nothing tells us how to make one. It would mean lossless power lines and cheap strong magnets. Searches, some machine-assisted, continue. The useful habit LK-99 taught is the three-part test above, and it applies to every future claim.

Learn the physics

• The Ledger: claims scored when the deadline lands

Sources

• Zhu et al. 2023: first-order transition in LK-99 containing Cu2S (arXiv)
• Jain 2023: copper(I) sulfide and LK-99 (arXiv)
• Deng et al. 2026: 151 K at ambient pressure in Hg-1223 (PNAS, open copy)

See it in the swipe deck, with the other cards.