Soft superconductivity in covalent bismuth dihydride BiH$_2$ under extreme conditions
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arXiv
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| Format: | Preprint |
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2025
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| _version_ | 1866912394420158464 |
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| author | Guo, Jianning Semenok, Dmitrii V. Troyan, Ivan A. Zhou, Di Wang, Yulong Chen, Yuzhi Chen, Su Zhang, Kexin Wu, Xinyue Luther, Sven Helm, Toni Sadakov, Andrey V Usoltsev, Alexey S. Morgun, Leonid A Pudalov, Vladimir M Struzhkin, Viktor V Huang, Xiaoli |
| author_facet | Guo, Jianning Semenok, Dmitrii V. Troyan, Ivan A. Zhou, Di Wang, Yulong Chen, Yuzhi Chen, Su Zhang, Kexin Wu, Xinyue Luther, Sven Helm, Toni Sadakov, Andrey V Usoltsev, Alexey S. Morgun, Leonid A Pudalov, Vladimir M Struzhkin, Viktor V Huang, Xiaoli |
| contents | 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 (BiH$_2$), successfully synthesized under pressure up to 211 GPa. The electrical resistance measurements indicate that the superconducting phase $P2_1/m$-BiH$_2$ exhibits the highest superconducting critical temperature ($T_c$) of 70 K among MH$_2$-type hydride apart from H$_2$S. The electrical transport experiments under both pulsed (up to 50 T) and steady magnetic fields (up to 16 T) for $P2_1/m$- and $C2/m$-BiH$_2$ indicate that the upper critical fields $μ_0 H_{c2}(0)$ = 12--16 T are unusually low, much lower than that of clathrate-like metal polyhydrides with similar $T_c$. This is due to the unexpectedly high Fermi velocity in BiH$_2$, about $1.1 \times 10^6$ m/s, which allows to classify BiH$_2$ 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 $J_c(0) = 10$ kA/mm$^2$), which indicates the presence of two $s$-wave superconducting gaps in BiH$_2$ at 172--176 GPa: $Δ_L(0) = 6.9 \pm 1.2$ meV and $Δ_S(0) \sim 1.5$ meV. |
| format | Preprint |
| id |
arxiv_https___arxiv_org_abs_2505_12062 |
| institution | arXiv |
| publishDate | 2025 |
| record_format | arxiv |
| spellingShingle | Soft superconductivity in covalent bismuth dihydride BiH$_2$ under extreme conditions Guo, Jianning Semenok, Dmitrii V. Troyan, Ivan A. Zhou, Di Wang, Yulong Chen, Yuzhi Chen, Su Zhang, Kexin Wu, Xinyue Luther, Sven Helm, Toni Sadakov, Andrey V Usoltsev, Alexey S. Morgun, Leonid A Pudalov, Vladimir M Struzhkin, Viktor V Huang, Xiaoli Superconductivity Classical Physics 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 (BiH$_2$), successfully synthesized under pressure up to 211 GPa. The electrical resistance measurements indicate that the superconducting phase $P2_1/m$-BiH$_2$ exhibits the highest superconducting critical temperature ($T_c$) of 70 K among MH$_2$-type hydride apart from H$_2$S. The electrical transport experiments under both pulsed (up to 50 T) and steady magnetic fields (up to 16 T) for $P2_1/m$- and $C2/m$-BiH$_2$ indicate that the upper critical fields $μ_0 H_{c2}(0)$ = 12--16 T are unusually low, much lower than that of clathrate-like metal polyhydrides with similar $T_c$. This is due to the unexpectedly high Fermi velocity in BiH$_2$, about $1.1 \times 10^6$ m/s, which allows to classify BiH$_2$ 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 $J_c(0) = 10$ kA/mm$^2$), which indicates the presence of two $s$-wave superconducting gaps in BiH$_2$ at 172--176 GPa: $Δ_L(0) = 6.9 \pm 1.2$ meV and $Δ_S(0) \sim 1.5$ meV. |
| title | Soft superconductivity in covalent bismuth dihydride BiH$_2$ under extreme conditions |
| topic | Superconductivity Classical Physics |
| url | https://arxiv.org/abs/2505.12062 |