Transformation of Hexagonal Lu to Cubic LuH$_{2+x}$ Single-Crystalline Films
Peiyi Li1,2†, Jiachang Bi2†, Shunda Zhang2, Rui Cai1,2, Guanhua Su2, Fugang Qi1,2, Ruyi Zhang2, Zhiyang Wei2,3, and Yanwei Cao2,3*
1School of Materials Science and Chemical Engineering, Ningbo University, Ningbo 315211, China 2Ningbo Institute of Materials Technology and Engineering, Chinese Academy of Sciences, Ningbo 315201, China 3Center of Materials Science and Optoelectronics Engineering, University of Chinese Academy of Sciences, Beijing 100049, China
Abstract：With the recent report of near ambient superconductivity at room temperature in the N-doped lutetium hydride (Lu–H–N) system, the understanding of cubic Lu–H compounds has attracted worldwide attention. Generally, compared to polycrystals with non-negligible impurities, the single-crystalline form of materials with high purity can provide an opportunity to show their hidden properties. However, the experimental synthesis of single-crystalline cubic Lu–H compounds has not been reported so far. Here, we develop an easy way to synthesize highly pure LuH$_{2+x}$ single-crystalline films by the post-annealing of Lu single-crystalline films (purity of 99.99%) in H$_2$ atmosphere. The crystal and electronic structures of films were characterized by x-ray diffraction, Raman spectroscopy, and electrical transport. Interestingly, Lu films are silver-white and metallic, whereas their transformed LuH$_{2+x}$ films become purple-red and insulating, indicating the possible formation of an unreported electronic state of Lu–H compounds. Our work provides a novel route to synthesize and explore more single-crystalline Lu–H compounds.
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2023, Vol. 40 
