Resonant inelastic x-ray scattering study the evolution of spin and charge excitations in La_2-xCe_xCuO₄ combi-films

We present resonant inelastic x-ray scattering (RIXS) study of spin and charge excitations in La_2-xCe_xCuO₄ combi-films. The doping level of the film changes continuously from one tip to the other, nominally x=0.10 to x=0.19. Doping dependence is accomplished by simply translating the film in a fine step along the doping gradient direction. We explored the evolution of spin and charge excitations from an optimal doped superconductivity at x=0.11 to an overdoped fermi liquid at x=0.18. As doping, the energy of both spin and charge excitations is hardening. For the width, the spin excitation is broadening, and the charge excitation becomes sharpening. In addition, we performed L and incident energy dependence measurements to examine the characteristics of two excitations. Spin excitation does not have L dependence nor incident energy dependence, while charge excitation has L dependence and slightly incident energy dependence. This indicates spin and charge excitations are not the two faces of the coin. Instead, spin and charge excitations are derived from short-range correlation and long-range Coulomb interaction, respectively.