Oxygen phonon branches in overdoped La1.7Sr0.3Cu3O4

The dispersion of Cu-O bond-stretching vibrations in overdoped La1.7Sr0.3CuO4 (not superconducting) has been studied by high-resolution inelastic neutron scattering. It was found that the doping-induced renormalization of the so-called breathing and half-breathing modes is larger than in optimally doped La1.85Sr0.15CuO4. On the other hand, the phonon linewidths are generally smaller in the overdoped sample. Features observed in optimally doped La1.85Sr0.15CuO4 which suggest a tendency towards charge stripe formation are absent in overdoped La1.7Sr0.3CuO4.