Symmetry-dependent electronic Raman scattering in La2-xSrxCuO4: Evidence for doping-induced change in the k-space anisotropy of charge dynamics

Low-frequency electronic Raman scattering in La2-xSrxCuO4 has been investigated over a wide compositional region, 0x0.34, covering the insulating, superconducting, and nonsuperconducting metallic compounds. We have found that the scattering intensity for the (xy) polarization predominates over that of the (xy) polarization in the low-doping region below x0.15, but vice versa at higher doping levels. The results indicate that anisotropy in the effective-mass tensor (or k-space dispersion) of the carriers changes systematically with hole doping, in contradiction with the simple band picture.