Direct spectroscopic evidence for completely filled Cu 3 d shell in BaCu 2 As 2 and α −</mml:mo…
2015; American Physical Society; Volume: 91; Issue: 23 Linguagem: Inglês
10.1103/physrevb.91.235109
ISSN1550-235X
AutoresShangfei Wu, P. Richard, Ambroise van Roekeghem, Simin Nie, H. Miao, Nan Xu, Tian Qian, Bayrammurad Saparov, Z. Fang, Silke Biermann, Athena S. Sefat, Hong Ding,
Tópico(s)Rare-earth and actinide compounds
ResumoWe use angle-resolved photoemission spectroscopy to extract the band dispersion and the Fermi surface of BaCu$_2$As$_2$ and $\alpha$-BaCu$_2$Sb$_2$. 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 BaCu$_2$As$_2$ 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$^{+1}$ oxydation state. However, the observation of Cu states at similar energy in $\alpha$-BaCu$_2$Sb$_2$ without the pnictide-pnictide interlayer bonding characteristic of the collapsed tetragonal phase suggests that the short interlayer distance in BaCu$_2$As$_2$ follows from the stability of the Cu$^{+1}$ rather than the other way around. Our results confirm the prediction that BaCu$_2$As$_2$ is an $sp$ metal with weak electronic correlations.
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