Direct observation of charge order in triangular metallic AgNiO2 by single-crystal resonant X-ray scattering.

Journal article

We report resonant x-ray scattering measurements on a single crystal of the orbitally degenerate triangular metallic antiferromagnet 2H-AgNiO2 to probe the spontaneous transition to a triple-cell superstructure at temperatures below T(S)=365  K. We observe a strong resonant enhancement of the supercell reflections through the Ni K edge. The empirically extracted K-edge shift between the crystallographically distinct Ni sites of 2.5(3) eV is much larger than the value expected from the shift in final states, and implies a core-level shift of ∼1  eV, thus providing direct evidence for the onset of spontaneous honeycomb charge order in the triangular Ni layers. We also provide band-structure calculations that explain quantitatively the observed edge shifts in terms of changes in the Ni electronic energy levels due to charge order and hybridization with the surrounding oxygens.

Authors: Pascut, G; Coldea, R; Radaelli, P; Bombardi, A; Beutier, G

• Publication status: Published
• Journal: Physical Review Letters
• Volume: 106
• Issue: 15
• Pages: 157206
• Publication date: 2011-04-01
• DOI: 10.1103/physrevlett.106.157206
• EISSN: 1079-7114
• ISSN: 0031-9007
• Language: English
• Keywords: cond-mat.str-el