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Résumé |
The theoretical description of the electronic structure of strongly correlated electron materials, such as unconventional superconductors [1], remains a great challenge. In fact, the electronic structure measured experimentally by means of state-of-the-art techniques, such as angle resolved photoemission spectroscopy, often differ from that calculated by means of mean-field approximation methods. To explain this discrepancy, we first show that, in strongly correlated electron materials, owing to the localized character of the electrons, the electronic structure can be successfully described by the electronic structure of local clusters [2], where atomic orbital quantum numbers can be used. The local cluster model helps us to understand physical properties such as the electron-phonon interaction based on bond order. Second, we discuss recent developments of crystallography based on the use of high-intensity quantum beams which enable to reveal local lattice distortions not detected by standard crystallographic analysis [3]. Third, we illustrate how the analysis of the magnetic excitation spectrum measured by means of inelastic neutron scattering can unveil electron correlations. Selected examples of structural and dynamical studies will be finally presented to illustrate the strong interplay between local structure and physical properties [4].
References
[1] Z. P. Yin, K. Haule and G. Kotliar, Nature Phys. 10 (2014) 845.
[2] A. Fujimori et al., Solid State Commun. 63 (1987) 857.
[3] T. Egami and S. J. L. Billinge, “Underneath the Bragg Peaks Structural Analysis of Complex Materials”, Pergamon (2003).
[4] S. Shamoto, to be submitted to a special issue “Frontiers of Spin, Orbital and Atomic Correlations by Neutron Scattering Study” of J. Phys. Soc. Jpn. |
