Electronic structure and phase separation of superconducting and nonsuperconducting K x Fe 2 - Y Se 2 revealed by x-ray photoemission spectroscopy

M. Oiwake, D. Ootsuki, T. Noji, T. Hatakeda, Y. Koike, M. Horio, A. Fujimori, N. L. Saini, Takashi Mizokawa

Research output: Contribution to journalArticle

10 Citations (Scopus)

Abstract

We have investigated the electronic structure of superconducting (SC) and nonsuperconducting (non-SC) KxFe2-ySe2 using x-ray photoemission spectroscopy (XPS). The spectral shape of the Fe 2p XPS is found to depend on the amount of Fe vacancies. The Fe 2p3/2 peak of the SC and non-SC Fe-rich samples is accompanied by a shoulder structure on the lower binding energy side, which can be attributed to the metallic phase embedded in the Fe2+ insulating phase. The absence of the shoulder structure in the non-SC Fe-poor sample allows us to analyze the Fe 2p spectra using a FeSe4 cluster model. The Fe 3d-Se 4p charge-transfer energy of the Fe2+ insulating phase is found to be ∼2.3 eV which is smaller than the Fe 3d-Fe 3d Coulomb interaction of ∼3.5 eV. This indicates that the Fe2+ insulating state is the charge-transfer type in the Zaanen-Sawatzky-Allen scheme. We also find a substantial change in the valence-band XPS as a function of Fe content and temperature. The metallic state at the Fermi level is seen in the SC and non-SC Fe-rich samples and tends to be enhanced with cooling in the SC sample.

Original languageEnglish
Article number224517
JournalPhysical Review B - Condensed Matter and Materials Physics
Volume88
Issue number22
DOIs
Publication statusPublished - 2013 Jan 31
Externally publishedYes

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Photoelectron spectroscopy
Phase separation
Electronic structure
photoelectric emission
electronic structure
X rays
Charge transfer
shoulders
spectroscopy
x rays
charge transfer
Valence bands
Coulomb interactions
Fermi level
Binding energy
Vacancies
Cooling
binding energy
valence
cooling

ASJC Scopus subject areas

  • Condensed Matter Physics
  • Electronic, Optical and Magnetic Materials

Cite this

Electronic structure and phase separation of superconducting and nonsuperconducting K x Fe 2 - Y Se 2 revealed by x-ray photoemission spectroscopy. / Oiwake, M.; Ootsuki, D.; Noji, T.; Hatakeda, T.; Koike, Y.; Horio, M.; Fujimori, A.; Saini, N. L.; Mizokawa, Takashi.

In: Physical Review B - Condensed Matter and Materials Physics, Vol. 88, No. 22, 224517, 31.01.2013.

Research output: Contribution to journalArticle

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AU - Oiwake, M.

AU - Ootsuki, D.

AU - Noji, T.

AU - Hatakeda, T.

AU - Koike, Y.

AU - Horio, M.

AU - Fujimori, A.

AU - Saini, N. L.

AU - Mizokawa, Takashi

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