I will first address our ultrafast spectroscopy investigations of iron-based high temperature superconductors, showing that there is a ubiquitous positive correlation between the electron-phonon coupling strength λ and the superconducting Tc among all known series of iron-based superconductors. Then I will talk about our recent ultrafast spectroscopy investigations on topological materials, particularly the very rare experimental evidence of Weyl Node Annihilation in magnetic Weyl semimetal Co3Sn2S2 unveiled by spin-polarized ultrafast dynamics.
