Ultrafast carrier relaxation dynamics in single-layer cuprates

Using a femtosecond pump-probe optical technique, we measured the time-resolved change in reflectivity of three single-layer cuprate samples, including Bi2Sr2-xLaxCuO6+z, La2CuO4+y and La2-xSrxCuO4 grown on SrTiO3. We analyze the data in terms of a nonthermal electron relaxation model, and obtain quantitative agreement between the model and the data. The initial electron-electron thermalization process is much longer in the uperconducting samples as opposed to the overdoped nonsuperconducting sample, suggesting a bottleneck in electron thermalization process due to the presence of the superconducting gap.