Press Releases
Jul. 30, 2007

Direct observation of “heavy electrons” in a superconductor

— Itinerant-to-localized transition disclosed —

Electrons in solids are generally categorized into “itinerant” electrons and “localized” ones. On the other hand, so-called “heavy electrons” in some compounds are known to exhibit both characters, namely, itinerant character at low temperatures and localized character at high temperatures, in their thermodynamic and transport properties, and their precise behaviors and origin have remained mysteries since their discovery 30 years ago.

Very recently, the research team of Dr. S.-I. Fujimori, Dr. Y. Haga (JAEA), Dr. A. Fujimori (Univ. of Tokyo), Dr. H. Yamagami (Kyoto Sangyo Univ.), Dr. Y. Onuki (Osaka Univ.) and their colleagues has succeeded in the direct observation of itinerant-to-localized transition in a heavy-electron superconductor UPd2Al3 with the technique of angle-resolved photoemission spectroscopy using synchrotron radiation from SPring-8. The result demonstrated for the first time the behaviors and the details of the itinerant and localized states and the transition between them in energy-momentum space. The present result will give new, deeper insight into not only heavy-electron superconductivity but also various types of unconventional superconductivity in solids.

This work has been published on-line in the July 1st, 2007 issue of Nature Physics.