Theory of Excitation Broadening Using Time-Dependent Density Functional Theory for Open Quantum Systems

Abstract

The Casida equations of linear response TDDFT are extended to calculate linear spectra of open quantum systems evolving according to a Markovian master equation. By mapping a many-body open quantum system onto an open, non-interacting Kohn-Sham system, extrinsic line broadening due to electron-bath coupling can be described exactly within TDDFT. The structure of the resulting matrix equations are analyzed for the generic case of electrons linearly coupled to a harmonic bath within Redfield theory. An approximate form of the exchange-correlation kernel based on first-order G"orling-Levy perturbation theory is derived.