Temperature and laser power dependence of femtosecond optical pair-breaking rate in optimally doped YBa₂Cu₃O_7-δ epitaxial thin films

Abstract

The temperature and laser power dependence of the femtosecond optical pair-breaking rate in optimally doped Y₁Ba₂Cu₃O_7-δ epitaxial thin films are studied. The temperature dependence is consistent with numerical simulations using the kinetic inductance model and the Rothwarf-Taylor theory. The laser power dependence shows strong nonlinear behavior. The magnitude of the nonlinearity, and its significant and systematic temperature and photon energy dependence, cannot be accounted for by the kinetic inductance model and the Rothwarf-Taylor theory, demonstrating the complexity of nonequilibrium superconductivity in high-temperature superconductors.