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arXiv · 2308.05222

Superionic phase transition of copper(I) sulfide and its implication for purported superconductivity of LK-99

Prashant K. Jain
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Abstract

Lee, Kim, and coworkers have recently claimed room-temperature and ambient-pressure superconductivity in a copper-doped lead apatite material named LK-99. However, the polycrystalline material synthesized has a significant fraction of copper(I) sulfide. Copper(I) sulfide has a known phase transition at 104 degrees C from an ordered low-temperature phase to a high-temperature superionic phase. As a result of this phase transition, copper(I) sulfide exhibits sharp transitions in electrical resistivity and heat capacity, which are expected to coincide with the temperature-induced transitions reported for LK-99. This implies that LK-99 must be synthesized without any copper(I) sulfide to allow unambiguous validation of the superconducting properties of LK-99.

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Prashant K. Jain. 2023-08-09. Superionic phase transition of copper(I) sulfide and its implication for purported superconductivity of LK-99. https://doi.org/10.1021/acs.jpcc.3c05684

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