| |
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. The properties aredirectly related to both the electronic structure and the atomic arrangement in the materials. To elucidate ε(Q, ω),therefore, the spectroscopic measurement becomes more critical beyond the basic structural characterization. Thequestion is how to measure it. Here I would like to focus on Inelastic X-ray Scattering (IXS), which has a potential toobserve the dynamical charge correlation in energy-momentum space, directly related to ε(Q ω).
IXS has become powerful technique at the third generation synchrotron facility (SR), like SPring-8, to investigatemomentum- and energy-dependent charge and lattice dynamics. The scattering amplitude of IXS, however, is verysmall. Then the application of IXS to surface/interface and the materials in nano-size is not easy and as a consequenceonly a few works have been reported for small number of scatterers such as surfaces and nano materials even ifthe third generation SR is used. In order to show how the IXS spectroscopy is a powerful technique for a researchin materials science I will show at first some of the results on high TC cuprates.1), 2) There is one hope to enhancescattering intensities for IXS, which is the resonance. This IXS is called Resonant IXS (RIXS). Since RIXS tunes theincident x-ray energy at the K-edge and/or L-edge of the constituent atom in the material, it can investigate the chargeexcitation of the selected element (element selectivity). Recently, we have applied RIXS to the Pt catalyst to investigatethe electronic states related to the catalytic activity. I will show the preliminary results on this system.
References:
1) S. Wakimoto et al., Phys. Rev. Lett. 102 (2009) 157001.
2) K. Ishii et al., Phys. Rev. Lett. 94 (2005) 207
|
