Rare-earth and actinide compounds

Rare-earth and actinide compounds host electrons that move so sluggishly through their crystal lattices that they behave as if their mass is hundreds of times heavier than a free electron — a phenomenon called heavy fermion behavior — and this unusual starting point gives rise to some of the most puzzling phases of matter in condensed matter physics, including superconductivity that cannot be explained by conventional theory. Researchers study how magnetic order, quantum critical points, and non-Fermi-liquid behavior emerge and compete in these materials, often by tuning temperature, pressure, or chemical composition to approach a zero-temperature phase transition where quantum fluctuations dominate. Central open questions include why superconductivity so often appears near the boundary between magnetic and non-magnetic states, what symmetry the superconducting order parameter actually breaks in specific compounds, and how the topology of the Fermi surface shapes these competing instabilities. Actinide metals such as uranium and plutonium add further complexity because their 5f electrons sit at the boundary between localized and itinerant behavior, making them both experimentally demanding and theoretically rich targets for understanding strongly correlated electron systems.

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107,105

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Keywords

Heavy FermionSuperconductivityQuantum CriticalityNon-Fermi-Liquid BehaviorFermi SurfaceUnconventional Superconductivity