Speaker
Description
The coherence of excitons, bound particle-hole pairs, is key for a number of non-equilibrium phenomena, including the amplification of ultrafast shift currents or “self-driven” exciton-Floquet effects. However, coherence is often suppressed by scattering processes on an ultrafast time scale. Still, such incoherent non-equilibrium states of excitons can have a profound impact on dynamical material properties. In this work, we investigate the effects of such long-lived non-equilibrium states for the single-particle spectral function and the signature in angle-resolved photoemission spectroscopy (ARPES). To this end, we employ the non-equilibrium Green’s function (NEGF) approach. To treat the excitons non-perturbatively, we use the particle-hole T-matrix. These calculations become tractable by using an efficient compressed representation in the exciton basis.