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Title: Direct spectroscopic evidence for completely filled Cu 3d shell in BaCu₂As₂ and α – BaCu₂Sb₂

We use angle-resolved photoemission spectroscopy to extract the band dispersion and the Fermi surface of BaCu₂As₂ and α - BaCu₂Sb₂. While the Cu 3d bands in both materials are located around 3.5 eV below the Fermi level, the low-energy photoemission intensity mainly comes from As 4p states, suggesting a completely filled Cu 3d shell. The splitting of the As 3d core levels and the lack of pronounced three-dimensionality in the measured band structure of BaCu₂As₂ indicate a surface state likely induced by the cleavage of this material in the collapsed tetragonal phase, which is consistent with our observation of a Cu⁺¹ oxidation state. However, the observation of Cu states at similar energy in α - BaCu₂Sb₂ without the pnictide-pnictide interlayer bonding characteristic of the collapsed tetragonal phase suggests that the short interlayer distance in BaCu₂As₂ follows from the stability of the Cu⁺¹ rather than the other way around. Our results confirm the prediction that BaCu₂As₂ is an sp metal with weak electronic correlations.
 [1] ;  [2] ;  [3] ;  [1] ;  [1] ;  [4] ;  [1] ;  [5] ;  [2] ;  [6] ;  [5] ;  [2]
  1. Chinese Academy of Sciences (CAS), Beijing (China)
  2. Chinese Academy of Sciences (CAS), Beijing (China); Collaborative Innovation Center of Quantum Matter, Beijing (China)
  3. Chinese Academy of Sciences (CAS), Beijing (China); Ecole Polytechnique, Palaiseau (France)
  4. Paul Scherrer Inst. (PSI), Villigen (Switzerland)
  5. Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)
  6. Ecole Polytechnique, Palaiseau (France); College de France, Paris (France); European Theoretical Synchrotron Facility (Europe)
Publication Date:
OSTI Identifier:
Publisher's Accepted Manuscript
Journal Name:
Physical Review. B, Condensed Matter and Materials Physics
Additional Journal Information:
Journal Volume: 91; Journal Issue: 23; Journal ID: ISSN 1098-0121
American Physical Society
Sponsoring Org:
Country of Publication:
United States