Strong Valence Fluctuation in the Quantum Critical Heavy Fermion Superconductor : A Hard X-Ray Photoemission Study
Physical review letters, 2010•APS
Electronic structures of the quantum critical superconductor β-YbAlB 4 and its polymorph α-
YbAlB 4 are investigated by using bulk-sensitive hard x-ray photoemission spectroscopy.
From the Yb 3 d core level spectra, the values of the Yb valence are estimated to be∼ 2.73
and∼ 2.75 for α-and β-YbAlB 4, respectively, thus providing clear evidence for valence
fluctuations. The valence band spectra of these compounds also show Yb 2+ peaks at the
Fermi level. These observations establish an unambiguous case of a strong mixed valence …
YbAlB 4 are investigated by using bulk-sensitive hard x-ray photoemission spectroscopy.
From the Yb 3 d core level spectra, the values of the Yb valence are estimated to be∼ 2.73
and∼ 2.75 for α-and β-YbAlB 4, respectively, thus providing clear evidence for valence
fluctuations. The valence band spectra of these compounds also show Yb 2+ peaks at the
Fermi level. These observations establish an unambiguous case of a strong mixed valence …
Electronic structures of the quantum critical superconductor and its polymorph are investigated by using bulk-sensitive hard x-ray photoemission spectroscopy. From the Yb core level spectra, the values of the Yb valence are estimated to be and for - and , respectively, thus providing clear evidence for valence fluctuations. The valence band spectra of these compounds also show 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 .
American Physical Society