Direct spectroscopic evidence for completely filled Cu $3d$ shell in BaCu$_2$As$_2$ and $Î±$-BaCu$_2$Sb$_2$

S. F. Wu; P. Richard; A. van Roekeghem; S. M. Nie; H. Miao; N. Xu; T. Qian; B. Saparov; Z. Fang; S. Biermann; Athena S. Sefat; H. Ding

doi:10.1103/PhysRevB.91.235109

paper

Direct spectroscopic evidence for completely filled Cu $3 d$ shell in BaCu $_{2}$ As $_{2}$ and $I^\pm$ -BaCu $_{2}$ Sb $_{2}$

arXiv:1504.00437 · doi:10.1103/PhysRevB.91.235109

Abstract

We use angle-resolved photoemission spectroscopy to extract the band dispersion and the Fermi surface of BaCu $_{2}$ As $_{2}$ and $I^\pm$ -BaCu $_{2}$ Sb $_{2}$ . While the Cu $3 d$ bands in both materials are located around 3.5 eV below the Fermi level, the low-energy photoemission intensity mainly comes from As $4 p$ states, suggesting a completely filled Cu $3 d$ shell. The splitting of the As $3 d$ 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 $I^\pm$ -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 $s p$ metal with weak electronic correlations.

6 pages, 4 figures

Direct spectroscopic evidence for completely filled Cu 3d shell in BaCu2​As2​ and I^±-BaCu2​Sb2​

Abstract

Direct spectroscopic evidence for completely filled Cu $3 d$ shell in BaCu $_{2}$ As $_{2}$ and $I^\pm$ -BaCu $_{2}$ Sb $_{2}$