National Synchrotron Radiation Research Center
○Yong Cai

Inelastic X-ray Scattering (IXS) is a powerful experimental technique that provides energy and momentum-resolved information on lattice and charge dynamics of a variety of condensed matters, and offers in particular unique strengths in the study of the low-energy charge excitations of correlated electron systems and the electronic properties of materials under extreme thermal dynamical conditions such as high pressure and extreme temperature. The technique has been widely implemented in third-generation synchrotron radiation sources around the world. The Taiwan Inelastic X-ray Scattering Beamline (BL12XU) at SPring-8 is designed for high-resolution resonant and non-resonant experiments on electronic excitations with energy ranges covering the K (L) absorption edges of most 3d (4f) metals. In this presentation, we will focus on non-resonant studies of low-energy charge excitations of a few archetypal materials, from collective excitations in MgB₂, exciton dynamics in organic polymers, to d-d excitations in Mott insulators, recently studied on the beamline, and discuss some of the interesting physics that can be unraveled using the technique. Potential of the technique in high pressure research will also be highlighted.

References:
[1]Y.Q. Cai, H.-K. Mao, P.C. Chow, J.S. Tse et al., “Ordering of hydrogen bonds in high-pressure low-temperature H₂O”. Phys. Rev. Lett. 94, 025502 (2005).
[2]Y.Q. Cai, P.C. Chow, O.D. Restrepo, Y. Takano, et al., “Low-Energy Charge Density Excitations in MgB₂: Striking Interplay between Single-Particle and Collective Behavior for Large Momenta”, Cond-Mat 0605320.
[3]N. Hiraoka, H. Ishii, I. Jarrige, and Y.Q. Cai, “Inelastic X-Ray Scattering Studies of Low-Energy Charge Excitations in Graphite”, Phys. Rev. B 72, 075103 (2005).