Abstract

Electrons in many strongly correlated materials fight two competing tendencies of becoming localized versus remaining itinerant. The resolution to this struggle often leads to fascinating phenomena such as high Tc superconductors, colossal magnetoresistance, and heavy fermions. I will present our recent results on the CeMIn5 (M = Co, Rh, Ir) family of heavy fermions. De Haas van Alphen results have shown that the f electron can be either localized or itinerant depending on the chemical composition or pressure. We have shown that the crossover from localized to itinerant occurs at the antiferromagnetic quantum critical point, where diverging fluctuations lead to interesting non-Fermi liquid physics, which can not be understood in the conventional framework of quantum phase transitions. I will then present several experiments from transport, thermodynamics, and ARPES which demonstrate the dual nature of electrons in various strongly correlated systems. Suggestions for unifying themes and future directions will be discussed.