Isotope Effect on Superconductivity in Solid Hydrogen

After decades of experimental progress on diamond anvil cells, researchers are able to squeeze solid hydrogen to pressures up to 450 GPa. In particular, two recent experiments by Loubeyre et al. employed infrared measurements to track the direct band gap and vibron frequency of hydrogen up to ~425 GPa [1] and deuterium up to ~460 GPa [2]. We previously argued that observed data is consistent with the molecular C₂/c-24 phase, which can explain the observed behavior up to ~425 GPa and above without requiring a structural phase transition [3]. The observations on deuterium strengthen our interpretation. We also previously reported the predicted superconducting properties of this phase as well as the other three most likely phases (Cmca-12, Cmca-4 and I4₁/amd-2) in the 400–500 GPa range [4,5]. In this work, we employ a Wannier function-based dense k-point and q-point sampling to compute the electron-phonon coupling and superconducting properties of solid deuterium in these four phases. In addition to their predictive nature, our findings will help future experiments distinguish between the candidate crystal phases.

[1] P. Loubeyre, F. Occelli, P. Dumas, Nature 577, 7792 (2020).

[2] P. Loubeyre, F. Occelli, P. Dumas, Phys. Rev. Lett. 129, 035501 (2022).

[3] M. Dogan, S. Oh, M. L. Cohen, J. Phys.: Condens. Matter 33, 03LT01 (2020).

[4] M. Dogan, S. Oh, M. L. Cohen, Phys. Rev. B 105, L020509 (2022).

[5] M. Dogan, S. Oh, M. L. Cohen, J. Phys.: Condens. Matter 34, 15LT01 (2022).