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RCQM/FCMP: Jianlin Luo: First order transition in LK-99 containing Cu2S

Talk Date: Tuesday, 8/29/2023, 2:30 PM Speaker: Dr. Jianlin Luo Institution: Institute of Physics, Chinese Academy of Sciences Title: First order transition in LK-99 containing Cu2S Organizer's note: The announcement of LK-99 as a possible room-temperature superconductor by the Korean group has excited the community, and there are many follow-up experiments trying to replicate the report. Prof. Lianlin Luo's group at the Institute of Physics, Chinese Academy of Science is one of the many groups. In this FCMP talk, Prof. Luo will summarize the progress in this short field, and provide key evidence suggesting that the original report of a resistivity drop above room temperature is due to an impurity phase in LK-99, unrelated to superconductivity. Abstract: The exploration of room-temperature superconductors at ambient pressure is the central focus of superconducting material research. Recently, Lee et al. reported that the compound LK-99, with a chemical formula of Pb10-xCux(PO4)6O (x from 0.9 to 1.1), exhibits room-temperature superconductivity under ambient pressure[1, 2]. This report immediately attracted widespread attention. In this presentation, I will provide a summary of the work carried out in this field. Furthermore, I will present a detailed introduction to the research conducted by our group. Specifically, we investigated the transport and magnetic properties of pure Cu2S and LK-99 containing Cu2S. We observed a sharp superconducting-like transition and a thermal hysteresis behavior in the resistivity and magnetic susceptibility. However, we did not observe zero resistivity below the transition temperature. Our findings strongly suggest that the so-called superconducting behavior in LK-99 is due to a reduction in resistivity caused by the first-order structural phase transition of Cu2S at around 385 K, from the β phase at high temperature to the γ phase at low temperature [3]. References: [1] S. Lee, J. H. Kim, & Y. W. Kwon, The first room-temperature ambient-pressure superconductor. arXiv:2307.12008 (2023). [2] S. Lee et al., Superconductor Pb10-xCux(PO4)6O showing levitation at room temperature and atmospheric pressure and mechanism. arXiv:2307.12037 (2023). [3] S. L. Zhu， W. Wu, Z. Li, and J. L. Luo, First order transition in Pb10-xCux(PO4)6O containing Cu2S，arXiv:2308.04353(2023).