Photoemission for f-electron materials

Thesis/Dissertation · Sun Jan 01 04:00:00 EST 1989

OSTI ID:7105618

Huang, Youngsea

The dissertation investigates the interpretation of photoemission from f-electron materials. The authors also discuss unusual room temperature solid-state reactions in Yb-Cu films that they discovered. They show the importance of considering the entire system in the photoemission process and that photoemission actually measures the energy difference between total energies of the initial state and the final excited state of the whole system. They point out misconceptions in the current interpretation of photoemission from mixed valent materials. Their results on Yb-Cu system and other high-resolution photoemission measurements on mixed valent Yb-based materials show that the 4f feature is not pinned at the Fermi level though there is a 4f{sup 14}(6s5d){sup 2} and 4f{sup 13}(6s5d){sup 3} configuration degeneracy in the ground state. They suggest that this non-pinning is a general phenomenon due to the fact that the final state is not completely relaxed in the photoemission process. They discuss the current competing models of photoemission from Ce-based materials and show problems with their interpretations. As 4f electrons are more itinerant for Ce and Yb, they give a delocalized-localized kind of interpretation for 4f levels of Ce based materials. They employ the Ce-Yb analogy (electron-hole inversion and thereby an energy scale inversion) with the impurity model to photoemission from Yb-based materials and point out contradictory results on YbAl{sub 3} in the literature. In their results on the Yb-Cu system, where the Yb valence varies from {approximately}3 to {approximately}2.2, they do not observe the Kondo resonance within the limits of their experimental resolution. They suggest that to date no Kondo resonance has been observed, and speculate either that the impurity model is inadequate for Yb-based materials or that photoemission is unable to detect a Kondo resonance.

• Research Organization: Boston Univ., MA (United States)
• OSTI ID: 7105618
• Country of Publication: United States
• Language: English

Related Subjects

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY
400201 -- Chemical & Physicochemical Properties
664200* -- Spectra of Atoms & Molecules & their Interactions with Photons-- (1992-)
74 ATOMIC AND MOLECULAR PHYSICS
ALLOYS
CERIUM ALLOYS
COPPER ALLOYS
DATA
ELECTRONIC STRUCTURE
EMISSION
ENERGY LEVELS
EXPERIMENTAL DATA
FERMI LEVEL
FILMS
INFORMATION
MATHEMATICAL MODELS
NUMERICAL DATA
PHOTOEMISSION
RARE EARTH ALLOYS
SECONDARY EMISSION
VALENCE
YTTERBIUM ALLOYS