Charge Order at the Frontier between the Molecular and Solid States in Ba3NaRu2O9

S. A. J. Kimber (1) , M. S. Senn (2) , Simone Fratini (3) , H. Wu (4) , A. H. Hill (1) , P. Manuel (5) , J. Paul Attfield (2) , D.N. Argyriou (6) , P. F. Henry (6)

1 ESRF - European Synchrotron Radiation Facility
2 School of Chemistry, Edinburgh
3 NEEL - TMC - Théorie de la Matière Condensée
4 Laboratory for Computational Physical Sciences, Surface Physics Laboratory and Department of Physics, Fudan University
5 RAL - STFC Rutherford Appleton Laboratory
6 HZB - Helmholtz-Zentrum Berlin für Materialien und Energie GmbH = Helmholtz Centre Berlin for Materials and Energy = Centre Helmholtz de Berlin pour les matériaux et l'énergie

We show that the valence electrons of Ba3NaRu2O9, which has a quasimolecular structure, completely crystallize below 210 K. Using an extended Hubbard model, we show that the charge ordering instability results from long-range Coulomb interactions. However, orbital ordering, metal-metal bonding, and formation of a partial spin gap enforce the magnitude of the charge separation. The striped charge order and frustrated hcp lattice of Ru2O9 dimers lead to competition with a quasidegenerate charge-melted phase under photoexcitation at low temperature. Our results establish a broad class of simple metal oxides as models for emergent phenomena at the border between the molecular and solid states.

Domaines: Electrons fortement corrélés [cond-mat.str-el]

S. A. J. Kimber, M. S. Senn, Simone Fratini, H. Wu, A. H. Hill, et al.. Charge Order at the Frontier between the Molecular and Solid States in Ba3NaRu2O9. Physical Review Letters, 2012, 108, pp.217205. ⟨10.1103/PhysRevLett.108.217205⟩. ⟨hal-00704541⟩