Surface hopping modeling of coherent charge and energy transfer in molecular materials and beyond

Surface hopping is probably the most popular approach to model energy transfer processes and other non-adiabatic phenomena, but its original formulation does not specify coherent elements of the involved density matrices. This complicates the application of surface hopping to ultrafast processes as well as to nonlinear spectroscopy, where these elements are critical. In this talk, I will describe our efforts to develop surface hopping into a fully coherent method. Notably, I will show that previous coherent implementations based on an inconsistent treatment of coherences and populations lead to unphysical density matrices, which may manifest as a violation of the Cauchy–Schwarz inequality and negative populations in the site basis. We recently developed a fully-consistent coherent implementation that does not suffer from such unphysical behavior. I will present a comparison of the method against numerically-exact results for a multichromophoric system representative of a light-harvesting complex. A high accuracy is found throughout most of parameter space, demonstrating its promise as a robust high-accuracy/low-cost method to study charge and energy dynamics in a broad variety of nanostructured materials.