Resonant inelastic X-ray scattering study of overdoped LaSrCuO

Wakimoto, Shuichi  ; Kim, Y.-J.*; Kim, H.*; Zhang, H.*; Gog, T.*; Birgeneau, R. J.*

Resonant inelastic X-ray scattering (RIXS) at the copper Kabsorption edge has been performed for heavily overdoped samplesof LaSrCuO with and . We have observed the chargetransfer and molecular orbital excitations which exhibit resonances at incident energies of and keV,respectively. From a comparison with previous results on undoped andoptimally-doped samples, we determine that the charge transfer excitation energy increases monotonically as doping increases. In addition, the -dependences of the RIXS spectral weight and absorption spectrum exhibit no clear peak at keV in contrast to results in the underdoped samples. The low-energy ( eV) continuum excitation intensity has been studied utilizing the high energy resolution of 0.13 eV (FWHM). A comparison of the RIXS profiles at and indicates that the continuum intensity exists even at in the overdoped samples, while it has been reported only at and for the sample. Furthermore, we also found an additional excitation on top of the continuum intensity at the and positions.