Observation of non-superconducting phase changes in LuH${}_{2\pm \text{x}}$N${}_y$

Abstract

The recent report of near-ambient superconductivity in nitrogen doped lutetium hydride has triggered a worldwide fanaticism and raised major questions about the latest claims. An intriguing phenomenon of color changes in pressurized samples from blue to pink to red was observed and correlated with the claimed superconducting transition, but the origin and underlying physics of these color changes have yet to be elucidated. Here we report synthesis and characterization of high-purity nitrogen doped lutetium hydride LuH${}_{2\pm \text{x}}$N${}_y$ with the same structure and composition as in the main phase of near-ambient superconductor1. We find a new purple phase of LuH${}_{2\pm \text{x}}$N${}_y$ between blue and pink phase, and reveal that the sample color changes likely stem from pressure-driven redistribution of nitrogen and its interaction with the LuH${}_2$ framework. No superconducting transition is found in all blue, purple, pink and red phases at temperatures 1.8-300 K and pressures 0-30 GPa. Instead, we identify a notable temperature-induced resistance anomaly of structural and/or electronic origin in LuH${}_{2\pm \text{x}}$N${}_y$, which is most pronounced in the pink phase and may have been erroneously interpreted as a sign of superconducting transition. This work establishes key benchmarks for nitrogen doped lutetium hydrides, allowing an in-depth understanding of the novel pressure-induced phase changes.

17 pages and 5 figures in the main text. 9 pages and 12 figures in the Supplementary Material. Any valuable comments and suggestions are warmly welcomed

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Cited by in corpus (11)

• Absence of near-ambient superconductivity in LuH${}_{2\pm \text{x}}$N${}_y$
• The near room-temperature upsurge of electrical resistivity in Lu-H-N is not superconductivity, but a metal-to-poor-conductor transition
• Temperature and quantum anharmonic lattice effects on stability and superconductivity in lutetium trihydride
• Microscopic theory of colour in lutetium hydride
• Electronic and magnetic properties of Lu and LuH${}_2$
• Anatomy of the band structure of the newest apparent near-ambient superconductor LuH${}_{3-x}$N${}_x$
• Unveiling a Novel Metal-to-Metal Transition in LuH2: Critically Challenging Superconductivity Claims in Lutetium Hydrides
• Superconductor discovery in the emerging paradigm of Materials Informatics
• Crystal structures and high-temperature superconductivity in molybdenum-hydrogen binary system under high pressure
• Evidence of Molecular Hydrogen in the N-doped LuH3 System: a Possible Path to Superconductivity?
• Phonon-mediated superconductivity in transition-metal trioxides XO3 (X = Ru, Re, Os, Ir, Pt) under pressure