Local moment, itinerancy and deviation from Fermi liquid behavior in Na${}_x$CoO${}_2$ for $0.71\le x\le 0.84$

Abstract

Here we report the observation of Fermi surface (FS) pockets via the Shubnikov de Haas effect in Na${}_x$CoO${}_2$ for $x=0.71$ and 0.84, respectively. Our observations indicate that the FS expected for each compound intersects their corresponding Brillouin zones, as defined by the previously reported superlattice structures, leading to small reconstructed FS pockets, but only if a precise number of holes per unit cell is \emph{localized}. For $0.71\le x<0.75$ the coexistence of itinerant carriers and localized $S=1/2$ spins on a paramagnetic triangular superlattice leads at low temperatures to the observation of a deviation from standard Fermi-liquid behavior in the electrical transport and heat capacity properties, suggesting the formation of some kind of quantum spin-liquid ground state.

4 pages, 4 figures

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• 1D to 2D Na Ion Diffusion Inherently Linked to Structural Transitions in Na${}_{0.7}$CoO${}_2$
• Sodium vacancy ordering and the co-existence of localized spins and itinerant charges in NaxCoO2
• Spin correlations and cobalt charge states: A new phase diagram of sodium cobaltates
• Na ordering imprints a metallic kagome lattice onto the Co planes of Na2/3CoO2
• Revealing the ortho-II Band Folding in YBa2Cu3O7-delta Films
• Correlation effects on the doped triangular lattice in view of the physics of sodium-rich Na${}_x$CoO${}_2$
• Magnetic fluctuations and specific heat in NaxCoO2 near a Lifshitz topological transition
• Electronic phase diagram of LixCoO2 revisited with potentiostatically de-intercalated single crystals
• Rearrangement of Sodium ordering and its effect on physical properties in $N{a}_{x}Co{O}_2$ system
• Oxygen non-stoichiometry and the origin of Na ion ordering in P2-NaxCoO2
• Considerable non-local electronic correlations in strongly doped Na${}_x$CoO${}_2$
• Na-ion dynamics in Quasi-1D compound NaV2O4
• From Hubbard bands to spin-polaron excitations in the doped Mott material Na${}_x$CoO${}_2$
• Synthesis of sodium cobaltate Na${}_x$CoO${}_2$ single crystals with controlled Na ordering
• New electronic orderings observed in cobaltates under the influence of misfit periodicities
• Ferrimagnetic ordering and spin entropy of field-dependent intermediate spins in Na0.82CoO2
• Revisiting the crystal electric field of P2-NaxCoO2 for the intermediate spin state of Co3+
• Interplay between strong correlations and electronic topology in the underlying kagome lattice of Na2/3CoO2
• Enhanced low energy fluctuations and increasing out-of-plane coherence in vacancy ordered NaxCoO2
• Ab-initio studying of spin states of sodium cobaltate Na${}_{2/3}$CoO${}_2$
• Sodium ion ordering of Na0.77CoO2 under competing multi-vacancy cluster, superlattice and domain formation