Unusual Electron Correlations in NaxCoO2 Due to the Spin-State Quasidegeneracy of Cobalt Ions
| Authors | |
|---|---|
| Year of publication | 2008 |
| Type | Article in Periodical |
| Magazine / Source | Progress of Theoretical Physics Supplement |
| MU Faculty or unit | |
| Citation | |
| Field | Solid matter physics and magnetism |
| Keywords | sodium cobaltates; superconductivity; electron correlations |
| Description | Recent studies exposed many remarkable properties of layered cobaltates NaxCoO2. Surprisingly, many-body effects have been found to increase at sodium-rich compositions of NaxCoO2 where one expects a simple, nearly free motion of the dilute S=1/2 holes doped into a band insulator NaCoO2. Here we discuss the origin of enigmatic correlations that turn a doped NaCoO2 into a strongly correlated electronic system. A minimal model including orbital degeneracy is proposed and its predictions are discussed. The model is based on a key property of cobalt oxides - the spin-state quasidegeneracy of CoO6 octahedral complex - which has been known, e.g., in the context of an unusual physics of LaCoO3 compound. Another important ingredient of the model is the 90 Co-O-Co bonding in NaxCoO2 which allows nearest-neighbor t2g-eg hopping. |
| Related projects: |