Strong electron-phonon coupling in the rare-earth carbide superconductor La2C3

J. S. Kim, Wenhui Xie, R. K. Kremer, V. Babizhetskyy, O. Jepsen, A. Simon, K. S. Ahn, B. Raquet, H. Rakoto, J.-M. Broto, and B. Ouladdiaf
Phys. Rev. B 76, 014516 – Published 24 July 2007

Abstract

We present the results of a crystal structure determination using neutron powder diffraction as well as the superconducting properties of the rare-earth sesquicarbide La2C3 (Tc13.4K) by means of specific-heat and upper critical field measurements. From the detailed analysis of the specific heat and a comparison with ab initio electronic structure calculations, a quantitative estimate of the electron-phonon coupling strength and the logarithmic average phonon frequency is made. The electron-phonon coupling constant is determined to be λph1.35. The electron-phonon coupling to low energy phonon modes is found to be the leading mechanism for superconductivity. Our results suggest that La2C3 is in the strong-coupling regime, and the relevant phonon modes are La related rather than C–C stretching modes. The upper critical field shows a clear enhancement with respect to the Werthamer-Helfand-Hohenberg prediction, consistent with the strong electron-phonon coupling. Possible effects on the superconducting properties due to the noncentrosymmetry of the crystal structure are discussed.

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  • Received 22 February 2007

DOI:https://doi.org/10.1103/PhysRevB.76.014516

©2007 American Physical Society

Authors & Affiliations

J. S. Kim, Wenhui Xie, R. K. Kremer, V. Babizhetskyy, O. Jepsen, and A. Simon

  • Max-Planck-Institut für Festkörperforschung, Heisenbergstraße 1, 70569 Stuttgart, Germany

K. S. Ahn

  • Department of Chemistry, Yonsei University, Wonju 220-710, South Korea

B. Raquet, H. Rakoto, and J.-M. Broto

  • Laboratoire National des Champs Magnétiques Pulsés, 143 Avenue de Rangueil, 31432 Toulouse, France

B. Ouladdiaf

  • Institute Laue-Langevin, Grenoble, Cedex 9, France

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Issue

Vol. 76, Iss. 1 — 1 July 2007

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