“Hot” electron generation in plasmonic nanostructures – thermal vs. non-thermal effects

We develop [Dubi & Sivan, Light Sci. Appl., 2019] a coupled Boltzmann-heat equations formulation for calculating the electron distribution in plasmonic nanostructures under continuous-wave illumination, taking into account non-equilibrium and thermal effects on the same footing. This approach allows us to determine self-consistently and uniquely the increase in electron and lattice temperatures above ambient conditions although the system is inherently away from thermal equilibrium. Our results provide the first-ever quantitative prediction of the high energy non-thermal electron densities, and show that close to the Fermi level, the non-equilibrium is dominated by holes (rather than by electrons)! Most importantly, we find that most absorbed power causes heating, and only an extremely small fraction actually leads to high energy electron generation. Finally, we develop a simple model for the catalytic enhancement for chemical reactions based on illuminated metal nanoparticles. It shows [Sivan et al., Science, 2019; Dubi et al., Chem. Sci., 2020] that the faster chemical reactions reported in many previous papers are extremely unlikely to originate from the high energy non-thermal electrons. Instead, the faster reactions very likely originate from a purely thermal effect.