Effect of Na content and hydration on the excitation spectrum of the cobaltite Na_xCoO_2 yH_2O

Abstract

We report on a Raman scattering study on the superconducting cobaltite $N{a}_{x}Co{O}_2\cdot y{H}_{2}O$ as function of Na content and hydration (x$\approx$1/3, 3/4 and y$\approx$0, 2/3, 4/3). The observed phonon scattering and scattering continua are analyzed in terms of lattice strain due to the structural misfit and disorder. Hydration, due to the intercalation of one or two $H_{2}O$ layers, releases a part of this strain. Our Raman data suggest a connection between disorder on the partly occupied Na sites, the split off of the $a_{1g}$ level from the other $t_{2g}$ states of $C{o}^{4+}$ and superconductivity.

10 pages, 4 figures, for further information see http://www.peter-lemmens.de

References in corpus (17)

• Time-Reversal Symmetry Breaking Superconductivity in Sr2RuO4
• Spin entropy as the likely source of enhanced thermopower in $\rm\bf Na_xCo_2O_4
• Superconductivity Phase Diagram of Na(x)CoO(2).1.3H(2)O
• An Electronic Model for $Co{O}_2$ layer based systems: Chiral RVB metal and Superconductivity
• Magnetic light scattering in low-dimensional quantum spin systems
• Unconventional magnetic transition and transport behavior in Na0.75CoO2
• Crystal Structure of the Sodium Cobaltate Deuterate Superconductor NaxCoO2o4xD2O (x=1/3)
• Structure and Dynamics of Superconducting NaxCoO(2) Hydrate and Its Unhydrated Analog
• Static magnetic order in Na${}_{0.75}$CoO${}_2$ detected by muon spin rotation and relaxation
• Instabilities of interacting electrons on the triangular lattice
• Possible spin triplet superconductivity in Na${}_x$CoO${}_2\cdot y$H${}_2$0
• Chemical Instability of the Cobalt Oxyhydrate Superconductor under Ambient Conditions
• Unconventional Upper- and Lower-Critical Fields and Normal-State Magnetic Susceptibility of the Novel Superconducting Compound $N{a}_{0.35}Co{O}_2\cdot 1.3H_{2}O$
• 59Co-NMR Knight Shift of the Superconducting NaxCoO2.yH2O
• Raman Phonons and Ageing-Related Surface Disorder in NaxCoO2
• Electron-phonon and spin-phonon coupling in NaV${}_2$O${}_5$: charge fluctuations effect
• Specific heat study of the Na(0.3)CoO(2).1.3H(2)O superconductor: influence of the complex chemistry

Cited by in corpus (9)

• The crystal growth and characterization of NaxCoO2 and NaxCoO2yH2O
• Raman Phonons and Ageing-Related Surface Disorder in NaxCoO2
• Structural Phase Transitions and Sodium Ordering in Na0.5CoO2: a Combined Electron Diffraction and Raman Spectroscopy Study
• Anomalous electronic Raman scattering in Na_xCoO_2 H_2O
• Raman Spectroscopy Study of alpha-, beta-, gamma-NaxCoO2 and gamma-(Ca,Sr)xCoO2
• First principles lattice dynamics of NaCoO${}_2$
• Rearrangement of Sodium ordering and its effect on physical properties in $N{a}_{x}Co{O}_2$ system
• Electron-phonon interaction in the lamellar cobaltate Na${}_x$CoO${}_2$
• Charge order and phonon renormalizations: Possible implications for cobaltates