The Optical Signatures of Stochastic Processes in Many-Body Exciton Scattering

We review our recent quantum stochastic model for spectroscopic lineshapes in the presence of a coevolving and nonstationary background population of excitations. Starting from a field theory description for interacting bosonic excitons, we derive a reduced model whereby optical excitons are coupled to an incoherent background via scattering as mediated by their screened Coulomb coupling. The Heisenberg equations of motion for the optical excitons are then driven by an auxiliary stochastic population variable, which we take to be the solution of an Ornstein-Uhlenbeck process. Here, we present an overview of the theoretical techniques we have developed as applied to predicting coherent nonlinear spectroscopic signals. We show how direct (Coulomb) and exchange coupling to the bath give rise to distinct spectral signatures and discuss mathematical limits on inverting spectral signatures to extract the background density of states.

Automated summary

In this paper, we review a recent quantum stochastic model for predicting spectroscopic signals, which takes into account the presence of coevolving and nonstationary background excitations. Starting from a field theory description and a simplified model, optical excitons are coupled to an incoherent background through scattering and screened Coulomb coupling. The Heisenberg equations of motion for the optical excitons are driven by an auxiliary stochastic population variable, modeled as a solution of an Ornstein-Uhlenbeck process. We discuss the distinct spectral signatures arising from direct and exchange coupling to the bath, as well as the mathematical limits on extracting the background density of states by inverting the spectral signatures.