Evidence for strong bound-electron-phonon interaction at 52 meV in YBa 2Cu 3O 7

Recent infrared and neutron scattering data provide evidence for strong electron-phonon coupling in the 52 meV/420 cm ^-1 range in YBa ₂Cu ₃O ₇. From a simple model of two coupled oscillators it is shown that a linear electron-phonon coupling can give the observed antiresonance structure in the frequency-dependent conductivity. We argue that the coupling is to the bound carriers responsible for the midinfrared absorption rather than to the superconducting free carriers.