Nonlinear ultrafast dynamics of high temperature YBa2Cu3O7–δ superconductors probed with THz pump / THz probe spectroscopyB. G. Perkins, H. Y. Hwang, N. K. Grady, L. Yan, D. Trugman, Q. Jia, H. T. Chen, A. J. Taylor and K. A. NelsonEPJ Web of Conferences, 41 (2013) 03010DOI: https://doi.org/10.1051/epjconf/20134103010