Strong valence fluctuation in the quantum critical heavy fermion superconductor β-YbAlB4: A hard x-ray photoemission study

M. Okawa*, M. Matsunami, K. Ishizaka, R. Eguchi, M. Taguchi, A. Chainani, Y. Takata, M. Yabashi, K. Tamasaku, Y. Nishino, T. Ishikawa, K. Kuga, N. Horie, S. Nakatsuji, S. Shin

*Corresponding author for this work

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85 Citations (Scopus)

Abstract

Electronic structures of the quantum critical superconductor β-YbAlB4 and its polymorph α-YbAlB4 are investigated by using bulk-sensitive hard x-ray photoemission spectroscopy. From the Yb 3d core level spectra, the values of the Yb valence are estimated to be ∼2.73 and ∼2.75 for α- and β-YbAlB4, respectively, thus providing clear evidence for valence fluctuations. The valence band spectra of these compounds also show Yb2 + peaks at the Fermi level. These observations establish an unambiguous case of a strong mixed valence at quantum criticality for the first time among heavy fermion systems, calling for a novel scheme for a quantum critical model beyond the conventional Doniach picture in β-YbAlB4.

Original languageEnglish
Article number247201
JournalPhysical Review Letters
Volume104
Issue number24
DOIs
Publication statusPublished - 2010 Jun 14
Externally publishedYes

ASJC Scopus subject areas

  • Physics and Astronomy(all)

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