Proposed insulating ground state of Na0.5 Co O2: Squaring the triangle

Ting Pong Choy, Dimitrios Galanakis, Philip Phillips

Research output: Contribution to journalArticlepeer-review


We demonstrate that at a filling of n=1.5, a hexatic insulating state obtains in the extended Hubbard model on a triangular lattice. Composed of two tetragonal sublattices with fillings of n=1 and n=2, the insulating state is charge ordered and possesses an antiferromagnetic superlattice with a dimension of a×3. Two distinct energy scales arise in our model: a charge gap for the insulator and the effective exchange interaction in the antiferromagnet. Our model is capable of explaining both qualitatively and quantitatively the Hall coefficient including the sign change, the temperature dependence of the resistivity, and the persistence of antiferromagnetism above the insulating state.

Original languageEnglish (US)
Article number073103
JournalPhysical Review B - Condensed Matter and Materials Physics
Issue number7
StatePublished - Feb 12 2007

ASJC Scopus subject areas

  • Electronic, Optical and Magnetic Materials
  • Condensed Matter Physics


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