The new frontier of nonequilibrium many-body physics and pump/probe experiments
Prof. Dr. Jim Freericks (Georgetown University)

There has been a recent resurgence of pump/probe experiments, where a large amplitude femtosecond laser pulse drives a material into a nonequilibrium state and then it is probed at different time delays with less intense femtosecond pulses that examine how the system transiently responds to being driven into nonequilibrium. While original experiments focused primarily on reflectivity studies, recent work has shifted more towards photoemission and X-ray diffraction. In addition to this activity on the experimental side, recent work in theory has shown how to extend the dynamical mean-field theory approach from equilibrium to nonequilibrium. In this talk, I will describe how one can formulate and solve the quantum many-body problem in nonequilibrium and will give examples of these solutions that cover the realm of pump/probe photoemission on electron-phonon coupled systems, discussing new sum rules, and novel behavior like the emergence of the Higgs mode in the superconducting state.