X-ray scattering studies of strongly correlated electron system

Valence electrons in strongly correlated electron systems are sometimes itinerant and sometimes localized. When they are localized, spatial modulations of charge, orbital, and spin degrees of freedom often arise. Synchrotron x-ray scattering measurements can provide information about the spatial arrangement of charges, orbitals and spin moments through scattering spectroscopies of core-electron excitations and precise analyses of spatial distribution of total electron density as well as atoms, and hence are regarded as a useful tool for studying the electronic states in strongly correlated electron systems. In future, spatial and temporal correlation of charge and magnetic moment may be measured as a function of not only reciprocal space and energy space but also real space and real time, which will open the door to the 'eight-dimensional measurements'. (author)