Phonon softening in NaxCoO2∙yH2O: Implications for the Fermi surface topology and the superconducting state
J.-P. Rueff, M. Calandra, M. d’Astuto, Ph. Leininger, A. Shukla, A. Bosak, M. Krisch, H. Ishii, Y. Cai, P. Badica, T. Sasaki, K. Yamada, K. Togano
DOI 10.1103/PhysRevB.74.020504 · Physical Review B
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Abstract
In this work we investigate the relevance of phonons for the superconductivity in Na0.35CoO2∙1.3H2O. We measure phonon dispersion in this material as well as in the nonhydrated parent compound Na0.7CoO2 by inelastic x-ray scattering. The measured phonon dispersion along the Γ−M direction shows a marked softening of Co-related optical phonon branches close to the Brillouin zone boundary, with hole doping. The phonon spectra, dispersion, and softening of Co-vibration modes are well reproduced by first-principles calculations. The critical temperature estimated from a phonon-mediated mechanism is much lower than the measured one, suggesting a nonconventional superconducting state in this material.
Source-reported materials — not catalogue approval
| Formula | Reported Tc (K) | Pressure (GPa) | Type |
|---|---|---|---|
| Na0.35CoO2*1.3H2O Archive — visibility unverified Source-occurrence policy only; no material identity or catalogue acceptance is inferred from the formula. | 4.6 | Pressure not reported | unknown |
| Na0.35CoO2 Archive — visibility unverified Source-occurrence policy only; no material identity or catalogue acceptance is inferred from the formula. | 0.15 | Pressure not reported | unknown |
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