Linear-Response Calculation of the Electron-Phonon Coupling in Doped CaCuO2

Using density-functional linear-response theory, we calculate the electron-phonon interaction for $s$- and $d$-wave pairing in the 0.24 hole doped infinite-layer compound ${\mathrm{CaCuO}}_2$. We find ${\lambda }_{x^2{-y}^2}\sim 0.3$ to be positive and only slightly smaller than ${\lambda }_s\sim \mathrm{0.4.}$ This suggests that the electron-phonon mechanism alone is insufficient to explain the high $T_c$ but could enhance another $d$-wave pairing mechanism. Results of calculated lattice dynamics and transport properties are also presented and discussed. Out-of-plane distortions are found essential for the stability.