Na${}_x$CoO${}_2$ in the x -> 0 Regime: Coupling of Structure and Correlation effects

Abstract

The study of the strength of correlations in Na${}_x$CoO${}_2$ is extended to the x=0 end of the phase diagram where Mott insulating behavior has been widely anticipated. Inclusion of correlation as modeled by the LDA+U approach leads to a Mott transition in the $a_g$ subband if U is no less than U${}_c$=2.5 eV. Thus U smaller than U${}_c$ is required to model the metallic, nonmagnetic CoO${}_2$ compound reported by Tarascon and coworkers. The orbital-selective Mott transition of the $a_g$ state, which is essentially degenerate with the $e_g^{\prime }$ states, occurs because of the slightly wider bandwidth of the $a_g$ bands. The metal-insulator transition is found to be strongly coupled to the Co-O bond length, due to associated changes in the $t_{2g}$ bandwidth, but the largest effects occur only at a reduced oxygen height that lies below the equilibrium position.

8 pages with 9 embedded figures

References in corpus (5)

• Ferromagnetic fluctuation and possible triplet superconductivity in Na_xCoO_2*yH_2O: Fluctuation-exchange study of multi-orbital Hubbard model
• Doping effects on the electronic and structural properties of CoO2: An LSDA+U study
• The Fermi surface of Na${}_x$CoO${}_2$
• Disproportionation Transition at Critical Interaction Strength: Na${}_{1/2}$CoO${}_2$
• Possible Pairing Symmetry of Superconductor Na_xCoO_2yH_2O

Cited by in corpus (5)

• Synthesis and properties of CoO2, the x = 0 end member of the LixCoO2 and NaxCoO2 systems
• Electronic Correlations in CoO2, the Parent Compound of Triangular Cobaltates
• Elliptical hole pockets in the Fermi surfaces of unhydrated and hydrated sodium cobalt oxides
• Electrochemical synthesis and properties of CoO2, the x = 0 phase of the AxCoO2 systems (A = Li, Na)
• Disproportionation and Critical Interaction Strength in Na${}_x$CoO${}_2$: Concentration Dependence