Consequences of Having Two Kinds of F-Electrons for Sce Systems as Treated By a Synthesis of Many-Body Theory and Electronic Structure

Abstract

For strongly correlated electron (SCE) systems, one has to treat at least two-electron dynamics and to include both p/d band -f hybridization and p/d band-f coulomb exchange. However, the two great simplifications possible when considering magnetic ordering for uranium SCE systems have enabled us to make absolute material-specific predictions of alloying or high-pressure effects using Local Density Approximation (LDA) input into many-electron dynamics with only one non-ab-initio number (the baseline percentage division, for unalloyed material at ambient pressure, between occupied correlated-electron states having localized (magnetic) and those having delocalized (nonmagnetic) 5f electrons). Experimentally, the alloying effects can be dramatic, e.g. in UxLal-XS the magnetic ordering abruptly disappears at about 55% uranium. The theory is quite successful in its detailed absolute predictions, and this has important implications for the overall understanding of electronic behavior in SCE systems including heavy fermion systems. The key conclusion is that the hybridization, as kinematically restricted by exchange symmetry, leads to a chemical-environment-dependent sharp threshold for a drastic restructuring of the ground state in SCE systems with dramatic observable consequences. This restructuring is driven by the elimination of the localized-magnetic transition-shell electrons (f electrons for light actinide and cerium-based SCE materials, d electrons for transition-metal-oxide-based SCE materials).