Séminaire - Local structures and their physical effects - Shin-ichi Shamoto

INSP - Sorbonne Université - 4 place Jussieu - 75005 Paris - Barre 22-32, 2^e étage, salle 201

Jeudi 12 juillet 2018 à 11h

Shin-ichi Shamoto - Advanced Science Research Center, Japan Atomic Energy Agency, 319-1195, Japan.

Abstract

Nowadays, someone may believe that electronic structures are well understood theoretically in metals and semiconductors, even in strongly correlated electron materials [1]. At the same time, their crystal structures can also be predicted from their electronic structures. On the other hand, their electronic structures have been revealed  experimentally  by  modern  state-of-the-art  photoemission  spectroscopies such as angle resolved photoemission spectroscopy. Their results often show that there are some deviations from their calculated band structures with mean field approximation. In the strongly correlated electron materials, their electronic band structures can be described by electronic structures of their local clusters possibly due to the localized electron characters [2], where quantum numbers such as orbitals can be good measures at every atom. The local cluster model helps us to understand the physical properties such as electron-phonon interaction based on the bond orders. In addition, recent crystallographic developments with high-intensity quantum beams reveals local lattice distortions in crystalline materials which are hidden by standard crystallographic analysis [3]. The magnetic excitation spectrum measured by inelastic neutron scattering also suggests the importance of electron correlation.

Here, some of structural and dynamical studies will be introduced as examples of strong interplay between local structure and their 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.