Abstract
We have performed a photoemission study of YbInCu 4, which undergoes a first-order phase transition at T v ≃40 K between the low-temperature intermediate-valence state and the high-temperature local-moment state. The Yb 4 f photoemission peak (Kondo peak) just below the Fermi level, which probably originates from the subsurface region of the YbInCu 4 samples but tracks the valence transition in the bulk YbInCu 4, has been studied above and below T v . It has been found that the 4 f photoemission peak is shifted from ∼− 35 meV at 75 K to −40 meV at 7 K.By analyzing the 4 f peak position and the Yb valence in the two phases using the Anderson impurity model, we find that the bare 4 f level, which is located close to the Fermi level, is shifted downward and the hybridization strength decreases in going from the high-temperature to low-temperature phases.
Highlights
The isostructural ®rst-order transition in YbInCu4, which was ®rst found by Felner and Nowik in 1986 [1], has attracted much attention due to sudden changes in the transport and thermodynamic properties within a very narrow temperature range around Tv 40±70 K [1±4]
Photoemission spectroscopy (PES) is a direct probe of occupied electronic states and is expected to give clear information especially for Yb compounds, where the 4f level is mostly occupied and signals from the outermost atomic layer are energetically well separated from bulk signals [12]
The absolute value of the valence ofbulk' Yb deduced from the photoemission spectra is much smaller than that deduced from the magnetic susceptibility and the lattice constant
Summary
Fiskd aDepartment of Physics and Department of Complexity Science and Engineering, University of Tokyo, Bunkyo-ku, Tokyo 113-0033, Japan bDepartment of Physics, Faculty of Education, Gunma University, Maebashi 371-8510, Japan cLos Alamos National Laboratory, Los Alamos, NM 84545, USA dDepartment of Physics and NHMFL, Florida State University, Tallahassee, FL 32310, USA
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