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Actinides, Chemical bonding, Crystal structure, Crystallographic properties, Heavy-fermion compounds, Intermetallic compounds, Magnetism, Superconductivity
Abstract:
Superconductivity has been captivating humankind for more than a century—unimaginable breakthroughs were made and invaluable lessons were learned with perhaps the most important one being that this peculiar phenomenon still holds many surprises. When it comes to actinide-based superconductors, the number of known representatives is rather low. They have small energy scales, which restrict the upper bounds of critical temperatures, i.e., the highly sought-after room-temperature superconductor likely will not be an actinide-based one. However, the study of these peculiar materials can help fully understand what governs the magnitude of the critical temperature in other systems, allowing for a clever avenue toward improvement. In this review, a comprehensive analysis of actinide- and, in particular, uranium-based superconductors is presented, with an emphasis on the chemical bonding and its relation to the observed physical properties. Even more than 60 years after its discovery, the record value of the critical superconducting temperature among uranium-based materials is still being held by U6Fe with Tc = 3.8 K. This is particularly puzzling given much higher critical temperatures of ostensibly similar plutonium- and neptunium-based superconductors. It is therefore reasonable to assume that higher temperature uranium-based superconductors exist, but have not yet been discovered. When it comes to finding new materials and refining features that are responsible for the emergence of superconductivity in these systems, computational analyses are, unfortunately, not yet able to model such complex orbital configurations in a time- and cost-efficient way. The aspiration of this review is that perhaps a thorough empirical analysis can be used to discover new uranium-based superconductors and through this contribute to the general understanding of superconductivity. Due to the limited amount of data on uranium-based systems, just a rough direction is outlined below, with the hope that new members can be discovered and used to refine this approach over time. © 2019 Elsevier B.V.
