Thermodynamic properties and enhancement of diamagnetism in nitrogen doped lutetium hydride synthesized at high pressure

Journal Article · 13 March 2024 · Proceedings of the National Academy of Sciences of the United States of America

DOI: https://doi.org/10.1073/pnas.2321540121 · OSTI ID:2323962

Han, Yifeng ^[1]; Ou, Yunbo ^[2]; Sun, Hualei ^[3]; Kopaczek, Jan ^[4]; Leonel, Gerson J. ^[1]; Guo, Xin ^[5]; Brugman, Benjamin L. ^[1]; Leinenweber, Kurt  ^[1]; Xu, Hongwu ^[1]; Wang, Meng  ^[6]; Tongay, Sefaattin ^[2]; Navrotsky, Alexandra  ^[7]

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1. Center for Materials of the Universe, School of Molecular Sciences, Arizona State University, Tempe, AZ 85287
2. School for Engineering of Matter Transport and Energy, Arizona State University, Tempe, AZ 85287
3. School of Science, Sun Yat-Sen University, Shenzhen 518107, R.P. China
4. School for Engineering of Matter Transport and Energy, Arizona State University, Tempe, AZ 85287, Department of Semiconductor Materials Engineering, Faculty of Fundamental Problems of Technology, Wroclaw University of Science and Technology, Wrocław 50-370, Poland
5. Eyring Materials Center, Arizona State University, Tempe, AZ 85287
6. Center for Neutron Science and Technology, Guangdong Provincial Key Laboratory of Magnetoelectric Physics and Devices, School of Physics, Sun Yat-Sen University, Guangzhou 510275, R.P. China
7. Center for Materials of the Universe, School of Molecular Sciences, Arizona State University, Tempe, AZ 85287, School for Engineering of Matter Transport and Energy, Arizona State University, Tempe, AZ 85287

Nitrogen doped lutetium hydride has drawn global attention in the pursuit of room-temperature superconductivity near ambient pressure and temperature. However, variable synthesis techniques and uncertainty surrounding nitrogen concentration have contributed to extensive debate within the scientific community about this material and its properties. We used a solid-state approach to synthesize nitrogen doped lutetium hydride at high pressure and temperature (HPT) and analyzed the residual starting materials to determine its nitrogen content. High temperature oxide melt solution calorimetry determined the formation enthalpy of LuH _1.96 N _0.02 (LHN) from LuH ₂ and LuN to be −28.4 ± 11.4 kJ/mol. Magnetic measurements indicated diamagnetism which increased with nitrogen content. Ambient pressure conductivity measurements observed metallic behavior from 5 to 350 K, and the constant and parabolic magnetoresistance changed with increasing temperature. High pressure conductivity measurements revealed that LHN does not exhibit superconductivity up to 26.6 GPa. We compressed LHN in a diamond anvil cell to 13.7 GPa and measured the Raman signal at each step, with no evidence of any phase transition. Despite the absence of superconductivity, a color change from blue to purple to red was observed with increasing pressure. Thus, our findings confirm the thermodynamic stability of LHN, do not support superconductivity, and provide insights into the origins of its diamagnetism.

• Sponsoring Organization: USDOE
• Grant/Contract Number: SC0021987
• OSTI ID: 2323962
• Journal Information: Proceedings of the National Academy of Sciences of the United States of America, Journal Name: Proceedings of the National Academy of Sciences of the United States of America Journal Issue: 12 Vol. 121; ISSN 0027-8424
• Publisher: Proceedings of the National Academy of SciencesCopyright Statement
• Country of Publication: United States
• Language: English