Yttrium Superhydrides Revisited: Advanced Experimental and Theoretical Studies of YH$_6$, YH$_9$ and YH$_{10}$

Dmitrii V. Semenok; Pedro N. Ferreira; Di Zhou; Fabian Jőbstl; Andrey V. Sadakov; Kirill S. Pervakov; Burkhan I. Massalimov; Toni Helm; Ryosuke Akashi; Vladimir M. Pudalov; Viktor V. Struzhkin; Christoph Heil; Ivan A. Troyan

arXiv · 2608.11428

Yttrium Superhydrides Revisited: Advanced Experimental and Theoretical Studies of YH$_6$, YH$_9$ and YH$_{10}$

Dmitrii V. Semenok·Pedro N. Ferreira·Di Zhou·Fabian Jőbstl·Andrey V. Sadakov·Kirill S. Pervakov·Burkhan I. Massalimov·Toni Helm·Ryosuke Akashi·Vladimir M. Pudalov·Viktor V. Struzhkin·Christoph Heil·Ivan A. Troyan

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Abstract

Yttrium polyhydrides are benchmark materials in high-pressure superconductivity, yet several key properties of the Y-H system remain insufficiently characterized. Here we combine contact transport, contactless radio-frequency measurements, pulsed-field experiments, and first-principles calculations to reinvestigate YH$_6$, YH$_9$, and YH$_{10}$ in the pressure range 140-213 GPa. Yttrium hydrides YH$_6$ ($\textit{$T_c$}$ = 218-221 K) and YH$_9$ ($\textit{$T_c$}$ = 235-237 K) demonstrate narrow superconducting transitions ($\textit{$Δ$T$_c$}$ = 2-5 K), approaching the limit imposed by thermal fluctuations. Pulsed-field measurements on YH$_6$ up to 60 T establish an extended superconducting phase diagram with a linear slope $\textit{dB$_{c2}$/dT}$ = -0.52 T/K, pronounced transition broadening above 30 T, and negligible normal-state magnetoresistance. We report the radio-frequency AC susceptibility study of YH$_6$, providing evidence for superconductivity via high-frequency field screening in a contactless geometry. Experiments involving Pd incorporation, Pd thin-film sputtering, and Al alloying show strong suppression of high-temperature superconductivity, with no transitions detected above 78-120 K. Finally, using density-functional theory with the stochastic self-consistent harmonic approximation, superconducting density-functional theory, and full-bandwidth Migdal-Eliashberg calculations, we show that anharmonic effects substantially reduce the predicted $\textit{$T_c$}$ of cubic YH$_{10}$ to approximately 260-270 K. These results strongly disfavor room-temperature superconductivity in binary yttrium superhydrides.

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Dmitrii V. Semenok, Pedro N. Ferreira, Di Zhou, Fabian Jőbstl, Andrey V. Sadakov, Kirill S. Pervakov, Burkhan I. Massalimov, Toni Helm, Ryosuke Akashi, Vladimir M. Pudalov, Viktor V. Struzhkin, Christoph Heil, Ivan A. Troyan. 2026-08-13. Yttrium Superhydrides Revisited: Advanced Experimental and Theoretical Studies of YH$_6$, YH$_9$ and YH$_{10}$. https://arxiv.org/abs/2608.11428

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