Synthesis and stability of high-T_c LaH_10±δ films at high pressures

Abstract

High-pressure hydrides hold the record for the highest superconducting critical temperatures across all classes of superconductors. Currently lanthanum decahydride, LaH₁₀, exhibits the highest critical temperature among binaries, with T_c ≈ 250 K at pressures between 140-180 GPa. Here, we report the synthesis of LaH_10±δ films in two DACs at pressures of 168 GPa and 176 GPa via in situ laser heating of elemental lanthanum films with ammonia borane (NH₃BH₃) as the hydrogen donor. The high-symmetry fcc lanthanum sublattice (space group Fm3̅m) is resolved using synchrotron X-ray diffraction, with unit cell parameters in excellent agreement with previous studies on bulk samples. We provide confirmation of high-T_c superconductivity in LaH_10±δ with highest T_c of 247 K at 176 GPa evidenced in electrical measurements. The characteristic suppression of superconductivity is observed in magnetic fields. Furthermore, combined diffraction and electrical measurements reveal remarkable temporal stability of both the crystal structure and the high-T_c superconductivity over the full measurement period of about 300 days post laser heating. Our work establishes film precursors using physical vapour deposition (PVD) techniques as a practical route to hydride formation, opening a pathway toward the controlled synthesis of promising ternary hydrides and the integration of micro-fabricated device geometries in diamond anvil cells.

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BibTeX RIS

BibTeX

@misc{cross2026synthesis,
  title = {{Synthesis and stability of high-$T_c$ LaH$_10\pmδ$ films at high pressures}},
  author = {Sam Cross and William Thomas and Lawrence Nobbs and Rebecca Nicholls and Oliver Lord and Qian Zhang and Dominique Laniel and Max Gerin and Bjorn Wehinger and Mohamed Mezouar and Xiaojiao Liu and Egor Koemets and Annette Kleppe and Sven Friedemann and Jonathan Buhot},
  howpublished = {arXiv},
  year = {2026},
  month = oct,
  doi = {10.48550/arxiv.2608.18865},
  eprint = {2608.18865},
  archivePrefix = {arXiv},
  url = {https://arxiv.org/abs/2608.18865},
  note = {CC BY 4.0},
}

RIS

TY  - UNPB
TI  - Synthesis and stability of high-T_c LaH_10±δ films at high pressures
AU  - Sam Cross
AU  - William Thomas
AU  - Lawrence Nobbs
AU  - Rebecca Nicholls
AU  - Oliver Lord
AU  - Qian Zhang
AU  - Dominique Laniel
AU  - Max Gerin
AU  - Bjorn Wehinger
AU  - Mohamed Mezouar
AU  - Xiaojiao Liu
AU  - Egor Koemets
AU  - Annette Kleppe
AU  - Sven Friedemann
AU  - Jonathan Buhot
PY  - 2026
DA  - 2026/10/20
PB  - arXiv
DO  - 10.48550/arxiv.2608.18865
UR  - https://arxiv.org/abs/2608.18865
AB  - High-pressure hydrides hold the record for the highest superconducting critical temperatures across all classes of superconductors. Currently lanthanum decahydride, LaH_10, exhibits the highest critical temperature among binaries, with T_c ≈ 250 K at pressures between 140-180 GPa. Here, we report the synthesis of LaH_10±δ films in two DACs at pressures of 168 GPa and 176 GPa via in situ laser heating of elemental lanthanum films with ammonia borane (NH_3BH_3) as the hydrogen donor. The high-symmetry fcc lanthanum sublattice (space group Fm3̅m) is resolved using synchrotron X-ray diffraction, with unit cell parameters in excellent agreement with previous studies on bulk samples. We provide confirmation of high-T_c superconductivity in LaH_10±δ with highest T_c of 247 K at 176 GPa evidenced in electrical measurements. The characteristic suppression of superconductivity is observed in magnetic fields. Furthermore, combined diffraction and electrical measurements reveal remarkable temporal stability of both the crystal structure and the high-T_c superconductivity over the full measurement period of about 300 days post laser heating. Our work establishes film precursors using physical vapour deposition (PVD) techniques as a practical route to hydride formation, opening a pathway toward the controlled synthesis of promising ternary hydrides and the integration of micro-fabricated device geometries in diamond anvil cells.
ER  -

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