Scientists Explain How the Best-Known Superconductor Works

Researchers from the Lebedev Physical Institute of RAS, and their associates from Japan, Germany, and the US discovered the mechanism that underlies the maximum temperature superconductivity in polyhydrides. The discovery was published in Advanced Materials, a weekly peer-reviewed scientific journal covering materials science. It opens the door to future research on materials that conduct electricity at room temperature or near it. These materials would be useful for superconducting electronics, quantum computers, MRI machines, and particle accelerators.

Near room temperature superconductors, while not the holy grail in materials science are among the most desired materials for technological applications. This material could allow for monster electromagnets. If it is discovered, it would be possible to use them in fundamental research instruments like ultraprecise magnet sensors and particle accelerators. Pure hydrogen, if squeezed hard enough, should theoretically be the best high-temperature superconductor. This is a difficult task to say the least. Instead, scientists are looking at compounds that have additional elements as well as plenty of hydrogen. They are doing this by sacrificing some temperature in order to lower pressures necessary to stabilize superconducting materials.

Professor Artem R. Oganov, the Principal investigator at Skoltech, commented that “Right now, the top contender in the superconductor race is lanthanum Superhydride LaH 10 with a critical temperature below minus 23°C.” This is a remarkable feat, but in order to take it further, we had to first understand how superconductivity works in this material. We now know, multiple mechanisms can be used to enable electrical conductivity without resistance. Conventional phonon-mediated superconductivity is the most well-known. It is due to electron interactions with crystal lattice oscillations. It is possible to use the well-known theory of conventional superconductivity to improve lanthanum-superhydride. This could be done by adding a crucial third element, which would create a new compound of hydrogen and two well-chosen elements.

“The problem is that we don’t have a model of a ternary superconducting system to determine how much we can improve superconducting properties for polyhydrides. There was also a lot of uncertainty that impeded and obscured progress in the search for near-room temperature superconductivity. Oganov stated that we have eliminated this uncertainty. Anderson’s theorem was widely used by his team to establish the behavior of superconductivity within lanthanum-superhydride. This theory states that conventional superconductors, and only them, retain their possessions when a nonmagnetic impurity is introduced, but experiences a decrease in critical temperature for superconductivity when magnetic impurities are added.

We dipped the material with magnetic neodymium after confirming in a previous paper that the addition ytrium, which is not magnetic, does not affect the critical temperature for superconductivity in the LaH 10. Dmitrii Semenok, a PhD scholar at Skoltech, was the lead author of the study. He said that superconductivity was suppressed as more neodymium was added. Researchers claim that we now have a better understanding about how impurities affect superconductivity of hydrides, and can predict many of these ternary hydroide systems’ properties. They will use the existing conclusions to predict, synthesize and test new three-element hydrogen-rich compounds.

This could improve on lanthanum suprahydride by increasing its critical temperatures or lowering the pressure of synthesis, or both. Our understanding and dispelling of myths regarding superconductivity has been enhanced by research into anomalous hydroide compounds. Oganov’s computer program USPEX was used to predict many of the counterintuitive compounds found at high pressures.