Japan Atomic Energy Agency has, in collaboration with Tohoku University, Kyoto Sangyo University and Osaka University, succeeded in observing Fermi surfaces (momentum distribution of the conduction electrons) of a plutonium compound, for the first time in the world.

Fermi surfaces, which is called as the "face" of metals, characterize most of physical properties of metals. Fermi surfaces of various compounds, including ordinary metals such as gold and superconducting materials, have been investigated to reveal the electronic properties of these materials. One of the powerful methods to observe Fermi surface is the quantum oscillation of magnetization which occurs at low-temperature under high magnetic fields for a very pure specimen. In plutonium compounds, however, the quantum oscillation has never been observed, due to their strong radioactivity which causes damage to the plutonium compound itself and lowers the quality of the specimen.

Very recently a plutonium compound PuIn3 with extremely high quality has been grown by the flux method by scientists at the Advanced Science Research Center, Japan Atomic Energy Agency. The sample was encapsulated to prevent the radioactive contamination and transported to the measurement facility rapidly to minimize the effect of radiation damage. As a result, they have succeeded in observing the quantum oscillation and determined the Fermi surfaces of PuIn3. They also found that the conduction electrons in PuIn3 have larger effective mass, several times heavier than that of the free electron, and move around the sample.

Plutonium, which is known as a nuclear material, is one of the most interesting elements because of its intriguing properties such as the multiple structural transformations. It was also reported recently that a plutonium-based superconductor with high-transition-temperature was discovered, attracting much scientific interest. The present observation that the 5f electron in plutonium compound moves around as conduction electrons will contribute in understanding the extraordinary high transition temperature of plutonium-based superconductors as well as the cuprate superconductor, an important material for the industrial application.

This result will be published as a Letter in the Journal of the Physical Society of Japan in the November issue. It was selected as one of the "Papers of Editors' Choice" of this journal.