Estimation of the electron-phonon coupling in ${\mathrm{YBa}}_2$${\mathrm{Cu}}_3$${\mathrm{O}}_7$ from the resistivity

Recent data on the single-domain resistivity of ${\mathrm{YBa}}_2$ ${\mathrm{Cu}}_3$ ${\mathrm{O}}_7$ are analyzed using the local-density-approximation calculations of the plasma frequencies and Fermi velocities. It is shown that the transport coupling constants ${\lambda }_{\mathit{t}\mathit{r}}$ for all three directions come out to be of the same order, namely about 1.5. The corresponding mean free path l=11 Å at T=300 K, which dispels the popular notion that the local-density-approximation band structure yields unreasonably large λ and small l values. The possibility of an anisotropy in ${\lambda }_{\mathit{t}\mathit{r}}$ and of a difference between λ and ${\lambda }_{\mathit{t}\mathit{r}}$ is discussed with the help of results from rigid-muffin-tin calculations of the Hopfield factors η.