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ε(Q, ω), dynamical dielectric function, is one of the most important quantities within the framework of a linerresponse theory in the condensed matter. To measure ε(Q, ω) experimentally in the wide energy and momentumspace is a key to understand the complex properties of not only bulk, but also nano materials. To elucidate ε(Q, ω),therefore, the spectroscopic measurement becomes more critical beyond the basic structural characterization. It isInelastic X-ray Scattering (IXS) that has a potential to observe the dynamical charge correlation in energy-momentumspace, directly related to ε(Q, ω). IXS has become powerful technique at the third generation synchrotron facility (SR),like SPring-8, to investigate momentum- and energy-dependent charge and lattice dynamics. An inelastic scatteringexperiment where electrons do not leave the system, like photoemission experiment, but makes a transition fromone state, which is below Ef, to another, which is above Ef, and therefore is a gentler spectroscopy since the systemis not violently changed during the process. There are two types of IXS: one is non-resonant, and another resonantIXS. (These are written as NIXS and RIXS, respectively.)1) In the talk, I will show the instrumentation and basics forboth NIXS and RIXS, and explain what kind of information we can get in the electronic properties from them, andshow some of the results on superconductors. The effect of phonons on superconductivity is always interesting tounderstand its mechanism. NIXS can study mostly the lattice dynamics even with a tiny single crystal, then the relationbetween the superconducting properties and the phonon can be investigated in superconductors of which the largesingle crystals are not available.2), 3) On the other hand, the RIXS can investigate the charge excitation of the selectedelement (atom) by incident X-ray energy being tuned at the K-edge of the atom. I will show the charge excitation of thehigh Tc Cu-oxide studied by RIXS, and discuss the future prospects.
References:
1) "Electro Dynamics by IXS", by W. Schulke, Oxford Science. 2007
2) M. Hoesch, et al., Phys. Rev. B 75 (2007) 140508(R).
3) T. Fukuda, et al., J. Phys Soc. Jpn. 77 (2008) 103715.
4) S. Wakimoto et al., Phys. Rev. Lett. 102 (2009) 157001.
Abstracts for School
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