Two-temperature model in plasmonic nanocrystals with complex shapes

The field of plasmonics has emerged as a novel way of manipulating the optical properties of nanomaterials upon illumination. Firstly, plasmonic nanocrystals (NCs) have shown promising uses, as their optical response can be manipulated through the careful design of their geometry; and secondly, plasmonic NCs generate heat efficiently in the presence of electromagnetic radiation. So, it is natural to wonder what opto-thermal effects occur in plasmonics NCs but with complex shapes. Here we tackle that question by studying the temporal dynamics of several complex-shape gold NCs. We use a two-temperature model to study the ultrafast photothermal responses, and we solve for the lattice and the electronic temperatures. We observe the creation of local modifications of the dielectric function via the temperature, which leads to the thermal imprint of plasmonic hotspots. Also, absorption signals are largely enhanced at the ultrafast timescales, showing that this is a general effect on all plasmonic NCs. Our results can lead to the design of ultrafast and optically reconfigurable nanophotonic devices.