Interpretation of resistivity of ${\mathrm{Nd}}_{1.85}$${\mathrm{Ce}}_{0.15}$${\mathrm{CuO}}_{4\mathrm{-}\mathit{y}}$ using the electron-phonon spectral function determined from tunneling data

Tunneling measurements of ${\mathrm{\alpha }}^2$F(ω) of ${\mathrm{Nd}}_{1.85}$ ${\mathrm{Ce}}_{0.15}$ ${\mathrm{CuO}}_{4\mathrm{-}\mathit{y}}$ are shown to be in good agreement with recent published results of the phonon density of states F(ω) from neutron scattering. The locations of peaks and valleys in both functions are similar, but the spectral weights differ, suggesting that ${\mathrm{\alpha }}^2$ has a strong energy dependence. We have used ${\mathrm{\alpha }}^2$F(ω) to estimate the phonon contribution, ${\mathrm{\rho }}_{\mathrm{phonon}}$(T), to published data of the temperature-dependent resistivity, ρ(T), for thin films and single crystals of ${\mathrm{Nd}}_{1.85}$ ${\mathrm{Ce}}_{0.15}$ ${\mathrm{CuO}}_{4\mathrm{-}\mathit{y}}$. When the phonon contribution is subtracted from the experimental data, a clear ${\mathit{T}}^2$ contribution remains over most of the temperature range. The ${\mathit{T}}^2$ contribution is interpreted to be due to three-dimensional electron-electron scattering, ${\mathrm{\rho }}_{\mathit{e}\mathrm{-}\mathit{e}}$. There is also a correlation between the magnitude of ${\mathrm{\rho }}_{\mathit{e}\mathrm{-}\mathit{e}}$, and the value of the plasma frequency, ${\mathrm{\omega }}_{\mathit{p}}$ [obtained from the determination of ${\mathrm{\rho }}_{\mathrm{phonon}}$(T)], with a scaling which approximates ${\mathrm{\omega }}_{\mathit{p}}^{\mathrm{-}10/3}$. Such a scaling is expected from the carrier-concentration dependence of electron-electron scattering.