Softening of Cu-O bond stretching phonon in tetragonal HgBa${}_2$CuO${}_{4+\delta }$

H. Uchiyama, A. Q. R. Baron, S. Tsutsui +5

Phonons in nearly optimally doped HgBa${}_2$CuO${}_{4+\delta }$ were studied by inelastic X-ray scattering. The dispersion of the low energy modes is well described by a shell model, while t…