New approach to the mixed valence problem

Thesis/Dissertation · Sun Jan 01 04:00:00 EST 1984

OSTI ID:6195497

Coleman, P

The mixed valence compounds are a class of rare earth compounds and alloys containing Ce, Sm, Eu, Tm, or Yb ions in which the 4f electrons are able to tunnel from well inside their rare earth hosts into the surrounding electron sea, giving rise to valence fluctuations between two atomic configurations of the rare earth ions. In these compounds, f electrons play and important role in conduction leading to many novel features in the equilibrium and transport properties. The electrons in the mixed valence compounds are highly correlated and the modelling of their behavior constitutes a strong coupling problem. This dissertation studies the mixed valence problem using the infinite U Anderson model to describe the hybridization of the f electrons with band electrons. Section 1 reviews the physical aspects of the mixed valence problem. Section 2 presents a new exact reformation of the Anderson model in which the singlet state of the rare earth ion is presented by a slave boson field and the spinning state by a spin j fermion. In this more convenient representation all operators obey standard commutation algebras and standard quantum field theory tools can be applied to the impurity and lattice problems. Section 3 examines the limit of large spin degeneracy N in the slave boson theory and shows this limit to be classical. 1/N plays the role of Planck's constant. The classical phase diagram is derived and the effects of quantum fluctuations at finite N studied. Section 4 applies scaling arguments to the Kondo lattice model and shows that large degeneracy enhances local spin fluctuations, leading to the stabilization of a non magnetic ground state with narrow band excitations.

• Research Organization: Princeton Univ., NJ (USA)
• OSTI ID: 6195497
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
360102 -- Metals & Alloys-- Structure & Phase Studies
37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY
400201* -- Chemical & Physicochemical Properties
ALLOYS
CERIUM ALLOYS
CERIUM COMPOUNDS
CRYSTAL LATTICES
CRYSTAL STRUCTURE
ELECTRONIC STRUCTURE
EUROPIUM ALLOYS
EUROPIUM COMPOUNDS
RARE EARTH ALLOYS
RARE EARTH COMPOUNDS
SAMARIUM ALLOYS
SAMARIUM COMPOUNDS
THULIUM ALLOYS
THULIUM COMPOUNDS
VALENCE
YTTERBIUM ALLOYS
YTTERBIUM COMPOUNDS