2025/05/17 by Jianning Guo, Dmitrii V. Semenok, Guo, Jianning +31 · 3 citations
Materials Science · Physics and Astronomy · #Classical Physics (physics.class-ph) #FOS: Physical sciences #Hydrogen Storage and Materials #Rare-earth and actinide compounds #Superconductivity (cond-mat.supr-con) #Superconductivity in MgB2 and Alloys
paper · pdf · doi:10.48550/arxiv.2505.12062
openalex publication_date 2025/05/17 · openalex created_date 2025/10/10 · openalex updated_date 2026/07/28
Strong magnetic fields provide a unique environment for investigating the fundamental properties of superconducting materials, especially for hydride superconductors with large upper critical fields. Following this idea, we have investigated the effect of pulsed magnetic fields on covalent bismuth dihydride (BiH2), successfully synthesized under pressure up to 211 GPa. The electrical resistance measurements indicate that the superconducting phase P21/m-BiH2 exhibits the highest superconducting critical temperature (Tc) of 70 K among MH2-type hydride apart from H2S. The electrical transport experiments under both pulsed (up to 50 T) and steady magnetic fields (up to 16 T) for P21/m- and C2/m-BiH2 indicate that the upper critical fields μ0 Hc2(0) = 12--16 T are unusually low, much lower than that of clathrate-like metal polyhydrides with similar Tc. This is due to the unexpectedly high Fermi velocity in BiH2, about 1.1 × 106 m/s, which allows to classify BiH2 as a 'soft' molecular superconducting hydride with relatively weak vortex pinning. Measurements of the current-voltage characteristics in the pulsed mode make it possible to experimentally establish the temperature dependence of the critical current density (the maximum Jc(0) = 10 kA/mm2), which indicates the presence of two s-wave superconducting gaps in BiH2 at 172--176 GPa: ΔL(0) = 6.9 ± 1.2 meV and ΔS(0) ∼ 1.5 meV.