We determined electronic relaxation times via pump-probe optical spectroscopy using sub-15 fs pulses for the normal state of two different cuprate superconductors.We show that the primary relaxation process is the electron-phonon interaction and extract a measure of its strength, the second moment of the Eliashberg function\lambda<\omega^{ 2}>=800\pm200 meV^{ 2} for La_{ 1.85}Sr_{ 0.15}CuO_{ 4} and \lambda<\omega^{ 2}>=400\pm100 meV^{ 2} for YBa_{ 2}Cu_{ 3}O_{ 6.5}. These values suggest a possible fundamental role of the electron-phonon interaction in the superconducting pairing mechanism.
Categories: cond-mat.supr-con