NaxCoO2: Enhanced low-energy excitations of electrons on a 2D triangular lattice

Abstract

To elucidate the low-energy excitation spectrum of correlated electrons on a 2D triangular lattice, we have studied the electrical resistance and specific heat down to 0.5 K and in magnetic fields up to 14 T, in NaxCoO2 samples with a Na content ranging from x \approx 0.5 to 0.82. Two distinct regimes are observed: for x from about 0.6 to x \approx 0.75 the specific heat is strongly enhanced, with a pronounced upturn of C/T below about 10 K, reaching 47 mJ/(mol K^2). This enhancement is suppressed in a magnetic field indicative of strong low-energy spin fluctuations. At higher Na content the fluctuations are reduced and mu-SR data confirm the SDW ground state below 22 K and the much reduced heat capacity is field independent.

arXiv commentAccepted in Physica B

References in corpus (6)

• Charge-ordering, commensurability and metallicity in the phase diagram of layered Na(x)CoO(2)
• Unconventional magnetic transition and transport behavior in Na0.75CoO2
• Static magnetic order in Na${}_{0.75}$CoO${}_2$ detected by muon spin rotation and relaxation
• Observation of Bulk Superconductivity in NaxCoO2.yH2O and NaxCoO2.yD2O Powder and Single Crystals
• Unconventional Charge Ordering in Na0.70CoO2 below 300 K
• Thermal and Electrical Properties of gamma-NaxCoO2 (0.70 < x < 0.78)

Cited by in corpus (7)

• Sachdev-Ye-Kitaev Models and Beyond: A Window into Non-Fermi Liquids
• Translationally invariant non-Fermi liquid metals with critical Fermi-surfaces: Solvable models
• Local moment, itinerancy and deviation from Fermi liquid behavior in Na${}_x$CoO${}_2$ for $0.71\le x\le 0.84$
• Magnetic fluctuations and specific heat in NaxCoO2 near a Lifshitz topological transition
• Spin fluctuations, magnetic long-range order and Fermi surface gapping in NaxCoO2
• Bad metallic transport in geometrically frustrated models
• Interplay between strong correlations and electronic topology in the underlying kagome lattice of Na2/3CoO2