From Hubbard bands to spin-polaron excitations in the doped Mott material Na${}_x$CoO${}_2$

Abstract

We investigate the excitation spectrum of strongly correlated sodium cobaltate within a realistic many-body description beyond dynamical mean-field theory (DMFT). At lower doping around $x$=0.3, rather close to Mott-critical half-filling, the single-particle spectral function of Na${}_x$CoO${}_2$ displays an upper Hubbard band which is captured within DMFT. Momentum-dependent self-energy effects beyond DMFT become dominant at higher doping. Around a doping level of $x\sim 0.67$, the incoherent excitations give way to finite-energy spin-polaron excitations in close agreement with optics experiments. These excitations are a direct consequence of the formation of bound states between quasiparticles and paramagnons in the proximity to in-plane ferromagnetic ordering.

5 pages, 3 figures; supplementary material

References in corpus (12)

• Continuous-time Monte Carlo methods for quantum impurity models
• Dynamical vertex approximation - a step beyond dynamical mean field theory
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• Strong Correlations Produce the Curie-Weiss Phase of Na${}_x$CoO${}_2$
• Local moment, itinerancy and deviation from Fermi liquid behavior in Na${}_x$CoO${}_2$ for $0.71\le x\le 0.84$
• Itinerant in-plane magnetic fluctuations and many-body correlations in Na${}_x$CoO${}_2$
• Polarization dependence of x-ray absorption spectra in Na_xCoO_2
• Correlation effects on the doped triangular lattice in view of the physics of sodium-rich Na${}_x$CoO${}_2$
• The origin of strong correlations and superconductivity in Na${}_x$CoO${}_2$

Cited by in corpus (5)

• Efficient fluctuation exchange approach to low-temperature spin fluctuations and superconductivity: from the Hubbard model to Na${}_x$CoO${}_2\cdot y$H${}_2$O
• Na order and Co charge disproportionation in Na${}_x$CoO${}_2$
• Origin of the electron disproportionation in the metallic sodium cobaltates
• Non-Fermi-liquid behaviour and Fermi-surface expansion induced by van Hove-driven ferromagnetic fluctuations: the D-TRILEX analysis
• Weak electronic correlations in the cobalt oxychalcogenide superconductor Na2CoSe2O