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Anomalous electronic Raman scattering in Na_xCoO_2 H_2O

P. Lemmens·K. Y. Choi·V. Gnezdilov·E. Ya. Sherman·D. P. Chen·C. T. Lin·F. C. Chou·B. Keimer
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Abstract

Raman scattering experiments on Na_{x}CoO_2 yH_2O single crystals show a broad electronic continuum with a pronounced peak around 100 cm-1 and a cutoff at approximately 560 cm-1over a wide range of doping levels. The electronic Raman spectra in superconducting and non-superconducting samples are similar at room temperature, but evolve in markedly different ways with decreasing temperature. For superconducting samples, the low-energy spectral weight is depleted upon cooling below T* sim 150K, indicating a opening of a pseudogap that is not present in non-superconducting materials. Weak additional phonon modes observed below T* suggest that the pseudogap is associated with charge ordering.

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P. Lemmens, K. Y. Choi, V. Gnezdilov, E. Ya. Sherman, D. P. Chen, C. T. Lin, F. C. Chou, B. Keimer. 2005-10-27. Anomalous electronic Raman scattering in Na_xCoO_2 H_2O. https://doi.org/10.1103/physrevlett.96.167204

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