Superconducting Praseodymium Superhydrides

TL;DR

This study reports the synthesis, structural phases, and superconducting properties of praseodymium superhydrides, revealing complex phases, magnetic interactions, and low-temperature superconductivity around 9K, advancing understanding of high-pressure superconductors.

Contribution

It is the first to synthesize and characterize PrH9 superhydrides, demonstrating their structural phases, magnetic properties, and superconductivity, expanding knowledge of rare-earth hydrides.

Findings

PrH9 synthesized in laser-heated diamond anvil cells.

Multiple structural phases identified, including F43m and P63/mmc.

Superconductivity observed below 9K, influenced by magnetic order.

Abstract

Superhydrides have complex hydrogenic sublattices and are important prototypes for studying metallic hydrogen and high-temperature superconductors. Encouraged by the results on LaH10, in consideration of the differences between La and Pr, Pr-H system is especially worth studying because of the magnetism and valence-band f-electrons in element Pr. Here we successfully synthesized praseodymium superhydrides (PrH9) in laser-heated diamond anvil cells. Synchrotron X-ray diffraction (XRD) analysis demonstrated the presence of previously predicted F43m-PrH9 and unexpected P63/mmc-PrH9 phases. Moreover, Fm3m-PrH3, P4/nmm-PrH(3-{\delta}) and Fm3m-PrH(1+x) were found below 52 GPa. F43m-PrH9 and P63/mmc-PrH9 were stable above 100 GPa in experiment. Experimental studies of electrical resistance in the PrH9 sample showed the emergence of superconducting transition (Tc) below 9K and a dependent Tc on applied magnetic field. Theoretical calculations indicate that magnetic order and electron-phonon interaction coexist in a very close range of pressures in the PrH9 sample which may contribute to its low superconducting temperature Tc. Our results highlight the intimate connections among hydrogenic sublattices, density of states, magnetism and superconductivity in Pr-based superhydrides.