Theory of photoinduced changes of the superfluid weight in superconductors

We investigate changes in superfluid weight in photo-excited states. This quantity is obtained by a microscopic calculation of the third-order nonlinear response function on the assumption that the pumping intensity is low. The resultant expression includes the energy dependence of self-energy explicitly. The importance of this dependence is shown by performing numerical calculations with the electron-boson interaction included. Moreover, it is found that the vertex correction makes a predominant contribution to the photoinduced change in superfluid weight. The similarity between the linear and photoinduced responses in its temperature dependence is discussed, and a quantitative estimation of the calculated results is made in comparison with that of the experiments. (author)