Doping dependence of softening in the bond-stretching phonon mode of LaSrCuO (00.29)

Fukuda, Tatsuo  ; Mizuki, Junichiro; Ikeuchi, Kazuhiko*; Yamada, Kazuyoshi*; Baron, A. Q. R.*; Tsutsui, Satoshi*

Phonons along the [100] direction, in particular the highest energy Cu-O bond-stretching LO mode, of LaSrCuO have been studied by inelastic X-ray scattering experiments. The LO phonon mode in the = 0.12 sample shows significant softening similar to early neutron studies. We show here a recovery of the softening was found in the = 0.29 sample, where superconductivity degrades and normal metallic conductivity dominates. The results suggest one-to-one correspondence between the softening of this LO phonon and the superconductivity.