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Ground-state oxygen holes and the metal-insulator transition in the negative charge-transfer rare-earth nickelates

Type of publication Peer-reviewed
Publikationsform Original article (peer-reviewed)
Author Bisogni Valentina, Catalano Sara, Green Robert J., Gibert Marta, Scherwitzl Raoul, Huang Yaobo, Strocov Vladimir N., Zubko Pavlo, Balandeh Shadi, Triscone Jean-Marc, Sawatzky George, Schmitt Thorsten,
Project Mott Physics Beyond the Heisenberg Model in Iridates and Related Materials
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Original article (peer-reviewed)

Journal NATURE COMMUNICATIONS
Volume (Issue) 7
Page(s) 13017
Title of proceedings NATURE COMMUNICATIONS
DOI 10.1038/ncomms13017

Open Access

URL http://www.nature.com/articles/ncomms13017
Type of Open Access Publisher (Gold Open Access)

Abstract

The metal–insulator transition and the intriguing physical properties of rare-earth perovskite nickelates have attracted considerable attention in recent years. Nonetheless, a complete understanding of these materials remains elusive. Here we combine X-ray absorption and resonant inelastic X-ray scattering (RIXS) spectroscopies to resolve important aspects of the complex electronic structure of rare-earth nickelates, taking NdNiO3 thin film as representative example. The unusual coexistence of bound and continuum excitations observed in the RIXS spectra provides strong evidence for abundant oxygen holes in the ground state of these materials. Using cluster calculations and Anderson impurity model interpretation, we show that distinct spectral signatures arise from a Ni 3d8 configuration along with holes in the oxygen 2p valence band, confirming suggestions that these materials do not obey a conventional positive charge-transfer picture, but instead exhibit a negative charge-transfer energy in line with recent models interpreting the metal–insulator transition in terms of bond disproportionation.
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