The dual nature of 5f electrons and origin of heavy fermions in U compounds

TL;DR

This paper presents a theory explaining the heavy fermion behavior in UPt$_3$ by proposing a dual nature of 5f electrons, with some localized and others delocalized, leading to large effective masses and specific electronic excitations.

Contribution

It introduces a model where two 5f electrons are localized and one is delocalized, explaining heavy fermion phenomena and anisotropic effective masses in UPt$_3$.

Findings

Explains deHaas-vanAlphen frequencies and heavy mass anisotropy

Shows only the largest 5f hopping matrix element is active

Reveals localization of electrons in orbitals with smaller hopping

Abstract

We develop a theory for the electronic excitations in UPt$_3$ which is based on the localization of two of the $5f$ electrons. The remaining $f$ electron is delocalized and acquires a large effective mass by inducing intra-atomic excitations of the localized ones. The measured deHaas-vanAlphen frequencies of the heavy quasiparticles are explained as well as their anisotropic heavy mass. A model calculation for a small cluster reveals why only the largest of the different $5f$ hopping matrix elements is operative causing the electrons in other orbitals to localize.