We have investigated the electronic structure of ${\mathrm{La}}_3{\mathrm{Ni}}_2{\mathrm{O}}_{7-\delta }$ $(\delta \approx 0.07)$ by means of hard x-ray photoemission spectroscopy (HAXPES). Although the nominal Ni valence is close to $+2.5$, the Ni $2p$ HAXPES spectra show an absence of ${\mathrm{Ni}}^{2+}/{\mathrm{Ni}}^{3+}$ charge disproportionation. The Ni $2p$ spectral shape including the main peak and the charge-transfer satellite indicate that oxygen $2p$ holes are heavily involved in the transport properties. The spectral weight suppression at the Fermi level indicates that the carriers of O $2p$ character (mixed with Ni $3d$) are affected by electronic correlation which would be associated with the density wave transition and the superconductivity controlled by pressure.

• Received 28 November 2023
• Revised 12 January 2024
• Accepted 16 February 2024

DOI:https://doi.org/10.1103/PhysRevB.109.125119

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Published by the American Physical Society