CU-O BOND-STRETCHING VIBRATIONS IN YBA(2)CU(3)0(7) STUDIED BY INELASTIC NEUTRON-SCATTERING

Inelastic neutron experiments confirm the previously reported anomalou s nature of the planar oxygen bond-stretching vibrations and furnish f urther details. It is shown that the frequency of the linear breathing mode is renormalized by 5 THz compared to insulating YBa2Cu3O6 Studie s of the Cu1-apical O bond-stretching vibrations demonstrate that freq uencies, line-widths and phonon intensities can well be understood wit hin the framework of a harmonic lattice dynamical model. This rules ou t predictions of a double well potential and strong anharmonitity for this type of vibration.