The establishment of coherent Bloch states in heavy Fermion materials involves entangling the f-spin degrees of freedom with those of the conduction electrons with corresponding change in the Fermi surface. Coherence only develops when excited crystal field levels become depopulated in heavy Fermions, intermediate valent materials belonging to a different regime of f-electron – conduction electron coupling. Kondo insulators are argued to be a particular instance of coherent behavior, with data from La₃Bi₄Pt₃ – Ce₃Bi₄Pt₃ alloys showing how coherence develops only at high Ce concentration.

【講師紹介】
Fisk教授は、重い電子系物質、特にCe化合物やU化合物の先駆的開発者であり、新物質開発の世界的な第一人者です。物性研究所ご来所の機会を得ましたので、これまでの研究されてきた重い電子系Ce化合物について、最近の研究も含めてご講演いただきます。