Phonon softening in HgBa2CuO4+δ observed by inelastic X‐ray scattering

Phonon dispersion of HgBa2CuO4+δ along the direction close to [100] was measured with using inelastic X-ray scattering. The longitudinal optical Cu-O bond stretching mode shows an anomalous softening at q ∼ 0.3, similar to reports for other high-Tc cuprates, such as YBa2Cu3O7–δ and La2–xSrxCuO4. This feature indicates a common property in the high-Tc cuprates, independent of lattice distortion and transition temperature. (© 2004 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)