Origin of strong correlations and superconductivity in NaxCoO2
Giniyat Khaliullin, Jiří Chaloupka
DOI 10.1103/PhysRevB.77.104532 · Physical Review B
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Abstract
We propose a minimal model resolving a puzzle of enigmatic correlations observed in sodium-rich NaxCoO2 where one expects a simple, free motion of the dilute S=1/2 holes doped into a band insulator NaCoO2. The model also predicts singlet superconductivity at experimentally observed compositions. The model is based on a key property of cobalt oxides—the spin-state quasidegeneracy of CoO6 octahedral complex—leading to an unusual physics of, e.g., LaCoO3. We show that correlated hopping between t2g and eg states leads to the spin-polaron physics at x∼1, and to an extended s-wave pairing at larger doping when coherent fermionic bands are formed.
Source-reported materials — not catalogue approval
| Formula | Reported Tc (K) | Pressure (GPa) | Type |
|---|---|---|---|
| NaxCoO2 Archive — visibility unverified Source-occurrence policy only; no material identity or catalogue acceptance is inferred from the formula. | 5 | Pressure not reported | unknown |
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