Signature of Multi-Band Magnetotransport in Superconducting Cerium Hydrides under Megabar Conditions

Hydride materials have achieved high superconducting transition temperatures (>250 K), albeit at pressures typically greater than 150 GPa, as reported in SH₃ or LaH₁₀.^1,2 These materials that exhibit high T_Cs, are accompanied by high critical magnetic fields H_C, such as CaH₆ which is predicted to have an H_C2 of 203 T.³ However, the constraints imposed by the instrumentation required for such pressures have limited the ability to adequately characterize the physical properties of many of these systems. In this study, we present magnetotransport measurements of the rare earth hydrides CeH₉ and CeH₁₀ conducted with pulsed magnetic fields by utilizing a miniature 9 mm outer diameter Diamond Anvil Cell.

We characterize both the cerium hydride and deuteride system using both X-ray and electrical probes to provide a more comprehensive understanding of the superconducting state. X-ray diffraction confirms both CeH₉ and CeH₁₀ are present along with their respective deuterated analogues. Pulsed magnetic field measurements were performed at fields as high as 59 T and pressures up to 130 GPa. We found that cerium hydride displaying a superconducting transition temperature of T_C of 122 K reaches an upper critical field (H_C2) of 40 T at 122 GPa, in agreement with a strong coupling model. Furthermore, we observe nonlinear Hall resistance indicating that the normal metal state of the cerium hydride system is multiband system.

1. Drozdov, A. P., Eremets, M. I., Troyan, I. A., Ksenofontov, V. & Shylin, S. I. Conventional superconductivity at 203 kelvin at high pressures in the sulfur hydride system. Nature 525, 73–76 (2015).

2. Drozdov, A. P. et al. Superconductivity at 250 K in lanthanum hydride under high pressures. Nature 569, 528–531 (2019).

3. Ma, L. et al. High-Temperature Superconducting Phase in Clathrate Calcium Hydride ${\mathrm{CaH}}_{6}$ up to 215 K at a Pressure of 172 GPa. Phys. Rev. Lett. 128, 167001 (2022).