Title: Low Energy Phonons in $Bi_2Sr_2CaCu_2O_{8+δ}$ and their Possible Interaction with Electrons Measured by Inelastic Neutron Scattering,
Abstract: Angle-resolved photoemission (ARPES) experiments on copper oxide
superconductors revealed enigmatic kinks in electronic dispersions near 10 meV
presumably due to phonons or impuritites. We used inelastic neutron scattering
to measure phonon branches below 15 meV in a large single crystal sample of
optimally-doped $Bi_2Sr_2CaCu_2O_{8+\delta}$ (BSCCO). The high quality dataset
covered several Brilloiun zones with different final energies. In addition to
acoustic branches, optic branches disperse from 4 meV and 7 meV zone center
energies. The 4 meV branch interacts with acoustic phonons at small
wavevectors, which destroys the LA character of the acoustic branch beyond
~0.15 reciprocal lattice units. We propose a mechanism that explains the low
energy electronic dispersion features based on this observation.