Spectral signature of non-equilibrium, high-density incoherent excitons

by Katja Moos (PSI)

Wednesday 20 May 2026, 15:00 → 16:00 Europe/Zurich

OVGA/200

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 nonequilibrium 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 nonequilibrium Green’s function (NEGF) approach. To treat the excitons non-perturbatively, we use the particlehole T-matrix. These calculations become tractable by using an efficient compressed representation in the exciton basis.