Research: Magnetic Hydrogen-Based Superconductor Discovered

2020-02-26

To create superconductivity at room temperature is one of today’s greatest challenges within research. Recently a hydrogen-based material with the rare-earth element lanthanum, a so-called superhydride, has raised hope that the ultimate answer to the puzzle could be close. Uppsala physicists have now been able to show that there are also other superhydrides, consisting of hydrogen atoms and the rare-earth element neodymium that are both magnetic and superconducting, and might be an unusual type of superconductor.

High temperature superconductivity was discovered in 2019 in a new type of materials consisting of hydrogen atoms and the rare-earth element lanthanum (La), a so-called superhydride. The material LaH10 became superconducting at 250 Kelvin, or -23 degrees Celsius, under very high pressure though, which is a disadvantage for technological applications. After this discovery, a global competition to synthesize other types of rare-earth superhydrides that could be more appropriate high-temperature superconductors at lower pressures was initiated.

In an international collaboration Alex Aperis and Peter Oppeneer from Uppsala University have together with researchers from Russia and China, produced previously unknown superhydrides with the rare-earth element neodymium (Nd). Especially interesting is the new material NdH9 which becomes superconducting at 5 Kelvin under high pressure. This transition temperature is low, but the material was discovered to be magnetic as well as superconducting, which is an extremely unusual combination. Usually magnetism and superconductivity mutually exclude each other.

With the help of the Uppsala Superconductivity code, developed at Uppsala University, the researchers carried out complex quantum mechanical calculations on the material and could from these explain why the material becomes superconducting at such a low temperature as 5 Kelvin. The magnetic field on the rare-earth neodymium atoms lowers the transition temperature considerably. But it is also the reason why an unconventional type of superconductivity can arise. Since the material is both magnetic and superconducting, two electrons with the same spin may form magnetic Cooper pairs. The researchers will carry out further experiments and calculations in order to examine if it is this rare type of superconductivity that we are dealing with.

– Our research shows in particular that there may very well be new exciting combinations of magnetism and superconductivity which can lead to the establishment of exotic material phases that until now have been unknown within solid state physics, says Alex Aperis, researcher at the Department of Physics and Astronomy.

Contact

Dr. Alex Aperis, phone 0769 212 312, alex.aperis@physics.uu.se

Article reference

D. Zhou et al, High-pressure synthesis of magnetic neodymium polyhydrides. J. Am. Chem. Soc. 142, 2803-2811 (2020), Publication Date: January 22, 2020, DOI: https://dx.doi.org/10.1021/jacs.9b10439

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Uppsala Superconductivity (UppSC) code

Camilla Thulin
English translation: Johan Wall