Inelastic-neutron-scattering study of the electron-phonon interaction in a superconductingLa1.85Sr0.15CuO4single crystal

Linewidths of some transverse acoustic phonons have been studied as a function of temperature on a superconducting single-crystal sample of ${\mathrm{La}}_{1.85}$${\mathrm{Sr}}_{0.15}$${\mathrm{CuO}}_{4}$ (${\mathit{T}}_{\mathit{c}}$=33 K) with the goal of measuring the electron-phonon interaction. The phonons studied have energies in the range \ensuremath{\omega}\ensuremath{\sim}6.0--9.5 meV and observed full widths at half-maximum in the range 2${\ensuremath{\gamma}}_{\mathrm{obs}}$\ensuremath{\sim}0.25--0.5 meV. No temperature-dependent changes were observed in any of the linewidths near the transition temperature. This null result is consistent with a low electronic density of states at the Fermi surface, and an electron-phonon coupling parameter \ensuremath{\lambda} that is not unusually high compared with conventional superconductors.