LK-99 (from the Lee-Kim 1999 research) is a potential room-temperature superconductor with a gray-black appearance, It is said to have a hexagonal structure that is slightly modified from lead‒apatite by adding small amounts of copper.

A team from Korea University led by Sukbae Lee (이석배) and Ji-Hoon Kim (김지훈) began studying this material in 1999. According to their claims, LK-99 acts as a superconductor at temperatures below 400 Kelvin (K) and at ambient pressure. As of 6 August 2023, the scientific community has not validated the superconductivity of LK-99 at any temperature through peer-reviewed processes or independent replication by other research groups. One preprint by a team from Southeast University, China has reported an observation of zero resistance at 110 K. However the absence of a well-defined phase transition, absence of the Meissner effect (a defining characteristic of superconductors), and the unique conditions under which these results were obtained raised doubts about the validity of the claim. Multiple other independent research teams are currently attempting to replicate the work of the South Korean team. Results are expected in August 2023, as the process of producing the material is said to be straightforward. The initial studies announcing the discovery of LK-99 were uploaded to the open-access repository of electronic preprints, arXiv. Lee later claimed the uploaded preprint papers were incomplete, and coauthor Hyun-Tak Kim (김현탁) stated that one of the papers contained defects.

Video

Pb9Cu(PO4)6(OH)2: Phonon bands, Localized Flat Band Magnetism, Models, and Chemical Analysis