Dave nλ=2dsinθ: "LK-99 isn’t a superconductor —…" - XtalDave's Mastodon

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Dave nλ=2dsinθ @xtaldave@xtaldave.net

LK-99 isn’t a superconductor — how science sleuths solved the mystery
#LK99 #Science
https://www.nature.com/articles/d41586-023-02585-7

In their preprint, the Korean authors note one particular temperature at which LK-99’s showed a tenfold drop in resistivity, from about 0.02 ohm-centimetres to 0.002 ohm-cm. “They were very precise about it. 104.8ºC,” says Prashant Jain, a chemist at the University of Illinois Urbana–Champaign. “I was like, wait a minute, I know this temperature.”

The reaction that synthesizes LK-99 uses an unbalanced recipe: for every 1 part copper-doped lead phosphate crystal — pure LK-99 — it makes, it produces 17 parts copper and 5 parts sulfur. These leftovers lead to numerous impurities — especially copper sulfide, which the Korean team reported in its sample.

Jain, a copper-sulfide expert, remembered 104ºC as the temperature at which Cu2S undergoes a phase transition. Below that temperature, the resistivity of air-exposed Cu2S drops dramatically — a signal almost identical to LK-99’s purported superconducting phase transition. “I was almost in disbelief that they missed it.” Jain published a preprint7 on the important confounding effect

Aug 17, 2023, 08:03 AM··Tusky

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