Low-q dispersion of transverse acoustic phonons in YBa${}_2$Cu${}_3$O${}_{7-\delta }$

Andrea Gauzzi, Matteo D'Astuto, Francesca Licci +2

High-resolution ($\Delta E$=1.3 meV) inelastic X-ray scattering (IXS) in optimally doped untwinned YBa${}_2$Cu${}_3$O${}_{7-\delta }$ single crystals show that the dispersion of transverse acoustic…