Interpretation of emergent excitonic and satellite features in RT-DE non-equilibrium spectra

Determine the exact physical interpretation of the emergent in-gap excitonic peak and the satellite band observed in the non-equilibrium time-resolved spectral function A(ω, t_p) computed with the real-time Dyson expansion (RT-DE) for the long-range interacting two-band Hubbard model with periodic boundary conditions under strong optical excitation; ascertain whether these features correspond to excitonic replicas or other boson-coupled satellite states and characterize their microscopic origin.

Background

In the periodic two-band Hubbard model example with long-range interactions driven by a below-gap pump, the RT-DE produces qualitative features absent in TD-HF and HF-GKBA, including a peak just below the renormalized conduction band and a satellite band below the equilibrium valence band. These features are suggestive of excitonic physics and possible bosonic replicas, but their precise nature has not been established.

The authors note that, while the RT-DE captures these emergent structures, the exact microscopic interpretation—e.g., whether the satellite constitutes an excitonic replica arising from simultaneous quasiparticle formation and exciton dissociation—requires further investigation. This unresolved issue is highlighted explicitly as future research.