Phonon `notches' in a-b -plane optical conductivity of high-Tc superconductors

Abstract

It is shown that a correlation between the positions of the $c$-axis longitudinal optic ($LO_c$) phonons and ``notch''-like structures in the $a$-$b$ plane conductivity of high-$T_c$ superconductors results from phonon-mediated interaction between electrons in different layers. It is found that the relative size of the notches depends on $\lambda_{ph}(\Omega_{ph}/\gamma_{ph})$, where $\lambda_{ph}$, $\Omega_{ph}$ and $\gamma_{ph}$ are the effective coupling strength, the frequency and the width of the optical phonon which is responsible for the notch. Even for $\lambda_{ph}\approx 0.01$ the effect can be large if the phonon is very sharp.