Superconductivity in thin film metal hydrides at megabar pressures

Metal hydrides at high pressures offer the prospect of finding superconductivity at room temperature [1, 2]. Our group at the University of Bristol has confirmed independently the presence of superconductivity below 200K in bulk H₃S [3]. We have also developed a new approach to synthesise hydride superconductors from an elemental thin film directly evaporated on the diamond anvil and ammonia borane (NH₃BH₃) as a hydrogen donor [4, 5]. This method facilitates the preparation of hydrides at megabar pressure and increases our success rate. In this talk, I will demonstrate the synthesis of YH₄ and LaH₄ thin films, which by having a lower T_c ≈ 40-80K (depending on pressure) allow us to study the critical field H_c2(T) over the full temperature range. I will present crystal structures obtained from x-ray diffraction, resistivity measurements as a function of temperature and magnetic field, and H_c2(T) extracted from DC and pulsed magnetic field measurements. I will also discuss remaining challenges in sample synthesis.



References

[1] A. P. Drozdov, et al. Nature 525, 73 (2015)

[2] A. P. Drozdov, et al. Nature 569, 528 (2019)

[3] I. Osmond et al. Phys. Rev. B 105, L220502 (2022)

[4] J. Buhot et al. Physical Review B 102, 104508 (2020)

[5] S. Cross et al. Physical Review B 109, L020503 (2024)