Transition from the Nanoscale to Bulk in the Nonequilibrium Optical Response of Laser-Dressed Materials

Understanding how the behavior of materials transitions from the nanoscale to bulk highlights properties where the finite size of matter matters. To date, such studies have focused on materials at or near thermal equilibrium, while this transition for strongly driven nonequilibrium systems is not understood. Here we investigate for the first time this transition for laser-dressed Floquet-engineered materials where resonant and nonresonant light is used to drive matter out of thermal equilibrium, creating an effective nonequilibrium material with properties that can be very different from those of pristine matter and that can be triggered on demand. As an archetypical example, we computationally characterize the linear optical absorption of laser-dressed trans-polyacetylene as a function of chain length, and also in bulk, using first-principle Hamiltonians and a recently proposed theory for the nonequilibrium optical response. The computations reveal nonequilibrium absorption sidebands that converge to equivalent features for bulk as the size of the system is increased, in a manner akin to near-equilibrium behavior. The computations also reveal nonequilibrium low-frequency features that emerge because of hybridization of Floquet states that show a persistent dependence on system size. We further demonstrate how resonant driving can be used to transform the isolated absorption peaks of a nanomaterial into broad bulk-like features. Overall, this work characterizes the structure-function relations in Floquet-engineered materials.