Increasing experimental evidence points towards a two-fluid model for the low-temperature behavior of 5f systems. Assuming some 5f electrons to be localized atomic-like and others to be band-like itinerant can explain various unusual low-energy properties of U compounds including the formation of heavy fermion and their unconventional superconductivity. The dual model, however, provides an effective Hamiltonian which is valid only for the low-energy regime. It has been shown that intra-atomic correlations among the 5f electrons are a possible mechanism for orbital-selective (partial) localization. In this paper we theoretically derive criteria and specify properties which experimentally characterize correlation-induced partial localization in actinide compounds. Of particular interest are the 5f spectral function which can be related to photoemission data. Results for the U -based heavy fermion superconductor UPd 2 Al 3 are presented emphasizing the consequences for the interpretation of experimental data.
Two fluid model in low energy excited states within spin-ice systems
