Monday Colloquium: Lara Benfatto (Sapienza University of Rome) "Manipulating matter with light: the case of superconductors"

Broken-symmetry states in condensed matter offer the unprecedented opportunity to observe collective electronic modes behaving as particle-like excitations. Superconductors offers a plethora of collective excitations connected to amplitude (Higgs) and phase (Goldstone) excitations of the superconducting order parameter, and their combinations in multiband superconductors (as the Leggett mode). However, their effect remains elusive in standard equilibrium spectroscopy, due to the weak coupling to light in ordinary conditions [1]. On the other hand, strong THz pulses trigger non-linear optical effects with specific selection rules, with the unprecedented possibility to access and manipulate several collective excitations [2-5]. In this talk I will review our progresses in the theoretical understanding of light-matter interaction in superconductors when non-linear optical effects come into play